It turns out that this topic has already been discussed several times on the Internet. Did Watson and Crick steal the double helix idea from Rosalind Franklin?

Janusz Wisniewski, about whom there was a post below, described this case as follows.

Rosalind Franklin, a graduate of the famous Cambridge, used in the early fifties a completely new technique of X-ray crystallography, discovered that DNA is a double helix, resembling a ladder, and its threads are phosphates. Her institute director John Randall presented the research findings, as well as the as-yet-unpublished insights of his young collaborator, in a narrow workshop attended by three people, including James Watson and Francis Crick. Shortly after that seminar, in March 1953, Watson and Crick published famous article, flawlessly describing the structure of the DNA double helix.

Modern genetics began that March. The world was numb with admiration. But not all. Rosalind Franklin suffered in silence while Watson and Crick were giving interviews, proudly entering history and reserving places for themselves in encyclopedias. She did not protest and never publicly “shared how she felt.

In 1958, Rosalind Franklin contracted cancer, although she was in good health and did not have any genetic prerequisites for this disease, and died a few weeks later.

She was thirty-seven years old.

In 1962, Watson and Crick received in Stockholm Nobel prize.

People also argue about whether Franklin would have been awarded the Nobel Prize if she had lived to this day.

And it seems to me that the story is quite ordinary. And for our time. It is clear that Crick and Watson took away the main thing from Franklin - priority. They questioned her primacy. Which discoverer is more important - a graduate student or a professor? The question is rhetorical. And in those days, it was generally difficult for a woman to object to men ..

What caused Rosalind Franklin to get cancer? From emotional distress or from the fact that she worked too much with X-rays? This, too, we will not know.

I think these two factors played the same role.

In short, even here the story of the discovery was not without a scandal. To be honest, it's a pity. I didn't know anything about Rosalind Franklin. I remember the photographs of Watson and Crick from childhood. My dad kept poking books "about science" in my nose. I remember their smiling insolent faces. And he didn't say anything about Rosalind. It's a pity. After all, you had to poke in and out of her photo, too, and say: “But this aunt did the wrong thing. She didn't fight. She was ashamed. And that's why she died. ”And you, girl, remember this and don't do that.

Double fertilization

the sexual process in angiosperms, in which both the egg and the central cell of the embryo sac are fertilized (see Embryo sac). Before. discovered by the Russian scientist S.G. Navashin in 1898 on two types of plants - lilies (Lilium martagon) and hazel grouse (Fritillaria orientalis). In D. about. both sperm are involved, brought into the embryonic sac by the pollen tube; the nucleus of one sperm (see Sperm) merges with the nucleus of the egg, the nucleus of the second - with the polar nuclei or with the secondary nucleus of the embryo sac. The embryo develops from a fertilized egg , from the central cell - Endosperm. In embryonic sacs with a three-celled egg apparatus, the contents of the pollen tube are usually poured into one of the synergids (See Synergids) , which at the same time collapses (the remnants of the synergistic nucleus and the vegetative nucleus of the pollen tube are visible in it); the second synergide subsequently dies off. Further, both sperm, together with the altered cytoplasm of the pollen tube, move into the slit-like space between the egg and the central cell. Then the sperm are dissociated: one of them enters the egg and comes into contact with its nucleus, the other enters the central cell, where it contacts the secondary nucleus or with one, and sometimes both, polar nuclei. Sperm lose their cytoplasm even in the pollen tube or upon penetration into the embryonic sac; sometimes sperm cells in the form of unchanged cells are observed in the embryo sac.

When D. about. the nuclei of the embryo sac are in interphase (see Interphase) and are usually much larger than the nuclei of the sperm, the shape and condition of which can vyryat. In skerda and some other Asteraceae, sperm nuclei have the appearance of a double twisted or twisted chromatin thread; in many plants they are elongated, sometimes twisted, more or less chromatized, without nucleoli; usually sperm are rounded interphase nuclei with nucleoli, sometimes not differing in structure from the female nuclei.

By the nature of the union of male and female nuclei, it is proposed (E. N. Gerasimova-Navashina) to distinguish two types of D. o .: premitotic - the sperm nucleus is immersed in the female nucleus, its chromosomes are despiralized; the unification of the chromosome sets of both nuclei occurs in the interphase (in the zygote); postmitotic - the male and female nuclei, preserving their shells, enter prophase (See Prophase) , at the end of which their union begins; interphase nuclei containing chromosome sets of both nuclei are formed only after the first mitotic division of the zygote. When D. about. 2 haploid nuclei merge in the ovum, therefore the nucleus of the zygote is diploid. The number of chromosomes in the nuclei of the endosperm depends on the number of polar nuclei in the central cell and on their ploidy (See Ploidy) ; the majority of angiosperms have 2 haploid polar nuclei and their endosperm is triploid. D.'s investigation about. - Xenia - manifestation of dominant signs of the endosperm of the parent plant in the endosperm of hybrid seeds. If several pollen tubes penetrate into the embryonic sac, the sperm of the first of them participate in D. of the lake, the sperm of the rest - degenerate. Cases of dyspermia, i.e. fertilization of an egg with two sperm, are very rare.

Lit .: S.G. Navashin, Fav. works, t. 1, M. - L., 1951; Mageshvar and P., Angiosperm embryology, trans. from English., M., 1954; Poddubnaya Arnoldi VA, General embryology of angiosperms, M., 1964; Steffen K., Fertilisation, in: Maheshwari P. (ed.). Recent advances in the embryology of angiosperms, Delhi, 1963.

I. D. Romanov.

Big Soviet encyclopedia... - M .: Soviet encyclopedia. 1969-1978 .

See what "Double fertilization" is in other dictionaries:

It is characteristic only of flowering plants. With double fertilization, one of the sperm fuses with the egg, and the second with the central cell of the embryo sac. An embryo develops from a fertilized egg, a secondary one from a central cell ... ... Big Encyclopedic Dictionary

A type of sexual process that is characteristic only of flowering plants. Discovered in 1898 by S.G. Navashin at the liliaceae. Before. lies in the fact that during the formation of the seed, not only the egg is fertilized, but also the center, the nucleus of the embryo sac. From the zygote ... ...

double fertilization- The type of sexual process characteristic of flowering plants: one of the sperm fertilizes the egg, and the other (from the same pollen tube) fertilizes the central nucleus of the embryo sac, as a result of the first process a diploid is formed ... ... Technical translator's guide

It is characteristic only of flowering plants. With double fertilization, one of the sperm fuses with the egg, and the second with the central cell of the embryo sac. An embryo develops from a fertilized egg, a secondary one from a central cell ... ... encyclopedic Dictionary

Double fertilization double fertilization. The type of sexual process characteristic of flowering plants: one of the sperm fertilizes the egg, and the other (from the same pollen tube ) fertilizes the central nucleus ... ... Molecular biology and genetics. Dictionary.

It is characteristic only of flowering plants. When D. about. one of the sperm fuses with the egg, and the second with the center. the cell of the embryo sac. The embryo develops from the fertilized egg, from the center. cells of the secondary endosperm of the seed, containing ... ... Natural science. encyclopedic Dictionary

double fertilization- the process of fertilization that occurs in angiosperms, in which both sperm formed are involved. One of them fuses with the egg, the second with the central diploid cell of the embryo sac. Discovered by S.G. Navashin in ... ... Plant anatomy and morphology

DOUBLE FERTILIZATION- the sexual process in angiosperms, which consists in the fusion of one male gamete by the pollen of the tube (sperm) with the egg of the embryo sac, and the second male gamete with the secondary nucleus of the embryo sac ... Dictionary of botanical terms

double fertilization by navash- PLANT EMBRYOLOGY DOUBLE FERTILIZATION ON NAVASHIN - the fusion of the egg and sperm with the formation of a zygote (2p) and the simultaneous fusion of another sperm and a double nucleus with the formation of the primary endosperm nucleus (3p). Salient feature all ... General Embryology: Glossary of Terminology

Syngamy, the fusion of the male reproductive cell (sperm, sperm) with the female (egg, ovum), leading to the formation of a zygote, the edge gives rise to a new organism. Animal O. is preceded by insemination. In the process of O., the egg is activated, ... ... Biological encyclopedic dictionary

Double fertilization, the sexual process in angiosperms, in which both the egg and the central cell of the embryo sac are fertilized. Double fertilization was discovered by the Russian scientist S.G. Navashin in 1898 on 2 plant species - lilies ( Lilium martagon) and hazel grouse ( Fritillaria orientalis). In double fertilization, both sperm are involved, brought into the embryonic sac by the pollen tube; the nucleus of one sperm merges with the nucleus of the egg, the nucleus of the second - with the polar nuclei or with the secondary nucleus of the embryo sac. The embryo develops from the fertilized egg, and the endosperm from the central cell. In embryonic sacs with a three-celled egg apparatus, the contents of the pollen tube are usually poured into one of the synergids, which is destroyed in this case (the remains of the synergid nucleus and the vegetative nucleus of the pollen tube are visible in it); the second synergide subsequently dies off. Further, both sperm, together with the altered cytoplasm of the pollen tube, move into the slit-like space between the egg and the central cell. Then the sperm are dissociated: one of them enters the egg and comes into contact with its nucleus, the other enters the central cell, where it contacts the secondary nucleus or with one, and sometimes both, polar nuclei. Sperm lose their cytoplasm even in the pollen tube or upon penetration into the embryonic sac; sometimes sperm cells in the form of unchanged cells are observed in the embryo sac.

With double fertilization, the nuclei of the embryo sac are in interphase and are usually much larger than the nuclei of the sperm, the shape and condition of which can vyryat. In skerda and some other Asteraceae, sperm nuclei have the appearance of a double twisted or twisted chromatin thread; in many plants they are elongated, sometimes twisted, more or less chromatized, without nucleoli; usually sperm are rounded interphase nuclei with nucleoli, sometimes not differing in structure from the female nuclei.

By the nature of the union of male and female nuclei, it is proposed (E. N. Gerasimova-Navashina) to distinguish two types of double fertilization: premitotic - the sperm nucleus is immersed in the female nucleus, its chromosomes are despiralized; the unification of the chromosome sets of both nuclei occurs in the interphase (in the zygote); postmitotic - the male and female nuclei, preserving their shells, enter a prophase, at the end of which they begin to unite; interphase nuclei containing chromosome sets of both nuclei are formed only after the first mitotic division of the zygote. With double fertilization, 2 haploid nuclei merge in the oocyte, therefore the nucleus of the zygote is diploid. The number of chromosomes in the endosperm nuclei depends on the number of polar nuclei in the central cell and on their ploidy; the majority of angiosperms have 2 haploid polar nuclei and their endosperm is triploid. The consequence of double fertilization - xenia - is the manifestation of the dominant traits of the endosperm of the parent plant in the endosperm of hybrid seeds. If several pollen tubes penetrate into the embryonic sac, the sperm of the first of them participate in double fertilization, the sperm of the rest - degenerate. Cases of dyspermia, i.e. fertilization of an egg with two sperm, are very rare.

Fertilization in angiosperms is preceded by micro- and megasporogenesis, as well as pollination.

Microsporogenesis proceeds in the anthers of the stamens. In this case, the diploid cells of the educational anther tissue as a result of meiosis are transformed into 4 haploid microspores. Over time microspore starts mitotic division and is converted into male gametophyte – pollen grain.

Pollen grain outside covered with two shells: exine and intina. Exina- the upper shell is thicker and impregnated with sporolenin, a fat-like substance. This allows the pollen to withstand significant thermal and chemical influences. The exine contains seedling pores, which were closed by "corks" before pollination. Intina contains cellulose and is elastic. There are two cells in a pollen grain: vegetative and generative.

Megasporogenesis carried out in ovule... From maternal nucellus cells as a result of meiosis, 4 megaspores are formed, of which only one remains. This megaspore grows strongly and pushes nucellus tissues towards integuments, forming embryo sac... The nucleus of the embryo sac is divided 3 times by mitosis. After the first division, the two daughter nuclei diverge to different poles: chalazal and micropilar, and there they are divided twice. Thus, there are four cores at each pole. Three nuclei at each pole separate into separate cells, and the remaining two move to the center and merge, forming a secondary diploid nucleus. On the micropilar pole there are two synergies and one larger cell - egg... At the halazal pole there are antipodes... Thus, a mature embryo sac contains 7 cells.

Pollination consists in the transfer of pollen from the stamens to the stigma of the pistil.

Fertilization... Pollen grains, which in one way or another got on the stigma, germinate. Pollen germination begins with the swelling of the grain and the formation of a pollen tube from the vegetative cell. The pollen tube breaks through the envelope in its thinner place - the so-called aperture. The tip of the pollen tube secretes special substances that soften the tissues of the stigma and column. As the pollen tube grows, the nucleus of the vegetative cell and the generative cell passes into it, which divides and forms two sperm. Through the micropyle of the ovule, the pollen tube penetrates into the embryonic sac, where it breaks, and its contents are poured inside. One of the sperm fuses with the egg to form a zygote, which then gives rise to the embryo of the seed. The second sperm fuses with the central nucleus, which leads to the formation of a triploid nucleus, which then develops into a triploid endosperm. In this way, endosperm in angiosperms triploid and secondary since formed after fertilization.

This whole process was named double fertilization... It was first described by the Russian scientist S.G. Navashin. (1898).

Antipodes and synergies dissolve after fertilization, and integuments are transformed into seed coat.

Apomixis- the development of an embryo from an unfertilized cell. The forms of apomixis depend on which parts of the ovule the embryo develops from. At parthenogenesis The (partheno-virgin) embryo arises from an unfertilized egg. If the embryo develops from any other cell of the gametophyte (antipodes, synergies), then this process is called apogamy... In the case of the formation of an embryo from nucellus cells, integuments that are not part of the gametophyte, they speak of apospory... Apomixis is common among evolutionarily advanced plant groups. Due to apomixis, plants do not depend on pollination agents

/>DOUBLE FERTILIZATION the sexual process in angiosperms, when both the egg and the center are fertilized. cell embryonic sac. Before. opened Russian. scientist S.G. Navashin in 1898 on 2 plant species - lilies (Lilium martagon) and hazel grouse (Fritillaria orientalis ) ... In D. about. both sperm are involved, brought into the embryonic sac by the pollen tube; core of one sperm merges with the nucleus of the egg , the nucleus of the second - with polar nuclei or with the secondary nucleus of the embryo sac. A fertilized egg develops embryo, from the center. cells - endosperm. In embryonic sacs with a three-celled facial apparatus, the contents of the pollen tube are usually poured into one of the synergid, which at the same time collapses (the remnants of the synergide nucleus and the vegetative nucleus of the pollen tube are visible in it ) ; the second synergide subsequently dies off. Further, both sperm, together with the altered cytoplasm of the pollen tube, move into the slit-like space between the egg and the center. cage. Then the spermatozoa dissociate: one of them enters the egg and comes into contact with its nucleus. , the other enters the central cell, where it comes into contact with the secondary nucleus or with one, and sometimes both, polar nuclei. Sperm lose their cytoplasm even in the pollen tube or when they enter the embryonic sac; sometimes spermatozoa in the form of unchanged cells are observed in

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embryonic sac.

Double fertilization; 1 - in hazel grouse: one of the sperm (a) is in contact with the egg nucleus, the second (b) - with one of the polar nuclei (the second polar nucleus is not shown); 2 - at sunflower; a - pollen tube; 6 - synergids (one of them is damaged by the pollen tube); c - egg cell; d - sperm in contact with the nucleus of the egg; d - central cell; e- the second sperm in contact with the secondary nucleus of the embryo sac.

When D. about. the nuclei of the embryo sac are in interphase and is usually much larger than the nuclei of sperm, the shape and condition to-ryh can vyryat. In skerda and some other Asteraceae, sperm nuclei have the form of a double twisted or twisted chromatin thread, in many others. plants they are elongated, sometimes twisted, b. or m chromatized, having no nucleoli; usually sperm are rounded interphase nuclei with nucleoli, sometimes not differing in structure from the female nuclei.

By the nature of the union of male and female nuclei, it was proposed (E. N. Ge-rasimova-Navashina) to distinguish two types of D. o .: premitotic - the sperm nucleus plunges into the female nucleus, its chromosomes are despiralized; the unification of the chromosome sets of both nuclei occurs in the interphase (in the zygote ) ; postmitotic - the male and female nuclei, preserving their shells, enter prophase, at the end of a cut, their unification begins; interphase nuclei containing chromosome sets of both nuclei are formed only after the first mitotic division of the zygote. When D. about. 2 haploid nuclei merge in the ovum, therefore the nucleus of the zygote is diploid. The number of chromosomes in the nuclei of the endosperm depends on the number of polar nuclei in the center. cage and from their ploidy; the majority of angiosperms have 2 haploid polar nuclei and endosperm, they have triploid. D.'s investigation about. - Xenia - manifestation of dominant signs of the endosperm of the parent plant in the endosperm of hybrid seeds. If several penetrates into the embryonic sac. pollen tubes, sperm of the first of them participate in D. of the lake, sperm of the rest - degenerate. Cases of dyspermia, i.e. fertilization of an egg with two sperm, are very rare.

A number of precise embryological studies on various representatives of angiosperms (lily, buttercups, asteraceae) S. G. Navashin convincingly showed that the endosperm, like the embryo, is a product of the sexual process. He called this unusual phenomenon, characteristic only of angiosperms, double fertilization. He announced his discovery in August 1898 at the 10th Congress of Russian Naturalists and Physicians held in Kiev, and in November of the same year published a short article on this topic in Izvestia of the Petersburg Academy of Sciences.

The idea of ​​the existence of double fertilization arose in S.G. Navashin as early as 1895 in the course of work on the study of chalazogamy in a walnut. This idea was finally confirmed and formalized into a coherent theory in the study of fertilization in a lily.

Later, S. G. Navashin described double fertilization in other flowering plants that are systematically far apart from each other - in representatives of buttercups, Compositae, walnut, thereby proving the generality of this phenomenon for all angiosperms.

Double fertilization is a distinguishing feature that separates angiosperms from gymnosperms.

The discovery by S.G. Navashin of double fertilization in angiosperms played important role in science.

The phenomenon of double fertilization clarified not only the question of the origin of endosperm, but also clarified the mysteriousness of such a phenomenon as xenia in corn. Navashin's work on the fertilization of angiosperms was met with great interest by botanists around the world.

Discussions about the essence of double fertilization continued at the beginning of the twentieth century. In the course of these discussions, and most importantly, thanks to new research, Navashin's conclusions were fully confirmed and further developed.

the sexual process in angiosperms, in which both the egg and the central cell of the embryo sac are fertilized. Before. discovered by the Russian scientist S.

G. Navashin in 1898 on 2 plant species - lilies (Lilium martagon) and hazel grouse (Fritillaria orientalis). In D. about. both sperm are involved, brought into the embryonic sac by the pollen tube; the nucleus of one sperm merges with the nucleus of the ovum, the nucleus of the second with the polar nuclei or with the secondary nucleus of the embryo sac. The embryo develops from the fertilized egg, and the endosperm from the central cell. In embryonic sacs with a three-celled egg apparatus, the contents of the pollen tube are usually poured into one of the synergids, which is destroyed in this case (the remains of the synergid nucleus and the vegetative nucleus of the pollen tube are visible in it); the second synergide subsequently dies off. Further, both sperm, together with the altered cytoplasm of the pollen tube, move into the slit-like space between the egg and the central cell. Then the sperm are dissociated: one of them enters the egg and comes into contact with its nucleus, the other penetrates into the central cell, where it contacts the secondary nucleus or with one, and sometimes both, polar nuclei. Sperm lose their cytoplasm even in the pollen tube or upon penetration into the embryonic sac; sometimes sperm cells in the form of unchanged cells are observed in the embryo sac.

When D. about. the nuclei of the embryo sac are in interphase and are usually much larger than the nuclei of the sperm, the shape and condition of which can vyryat. In skerda and some other Asteraceae, sperm nuclei have the appearance of a double twisted or twisted chromatin thread; in many plants they are elongated, sometimes twisted, more or less chromatized, without nucleoli; usually sperm are rounded interphase nuclei with nucleoli, sometimes not differing in structure from the female nuclei.

According to the nature of the union of male and female nuclei, it was proposed (E. N. Gerasimova-Navashina) to distinguish two types of D. o .: premitotic - the sperm nucleus plunges into the female nucleus, its chromosomes are despiralized; the unification of the chromosome sets of both nuclei occurs in the interphase (in the zygote); postmitotic - the male and female nuclei, preserving their shells, enter a prophase, at the end of which they begin to unite; interphase nuclei containing chromosome sets of both nuclei are formed only after the first mitotic division of the zygote. When D. about. 2 haploid nuclei merge in the ovum, therefore the nucleus of the zygote is diploid. The number of chromosomes in the endosperm nuclei depends on the number of polar nuclei in the central cell and on their ploidy; the majority of angiosperms have 2 haploid polar nuclei and their endosperm is triploid. D.'s investigation about. ≈ xenia ≈ manifestation of the dominant traits of the endosperm of the parent plant in the endosperm of hybrid seeds. If several pollen tubes penetrate into the embryonic sac, the sperm of the first of them participate in D. of the lake, the sperm of the rest - degenerate. Cases of dyspermia, i.e. fertilization of an egg with two sperm, are very rare.

Lit .: Navashin S.G., Fav. works, vol. 1, Moscow-Leningrad, 1951; Mageshvar and P., Angiosperm embryology, trans. from English., M., 1954; Poddubnaya Arnoldi VA, General embryology of angiosperms, M., 1964; Steffen K., Fertilisation, in: Maheshwari P. (ed.). Recent advances in the embryology of angiosperms, Delhi, 1963.

I. D. Romanov.

Double fertilization

Lecture Pollination

For the formation of the embryo, pollination and fertilization must occur.

Pollination- the process of transfer of pollen from the stamen to the stigma of the pistil. Pollination first appears in gymnosperms, but reaches the greatest perfection in angiosperms.

There are two types of pollination: self-pollination and cross-pollination. At self-pollination the pollen of the same plant falls on the pistil of a flower; if the transfer of pollen is carried out between the flowers of different individuals, then there is cross-pollination.

It is believed to be inherent in 90% of plants. Cross-pollination causes high level heterozygosity of populations. This creates great opportunities for natural selection. Severe self-pollination is relatively rare (for example, in peas) and can lead to the splitting of the species into a number of clean lines, i.e. makes populations homozygous.

For the evolutionary process, the optimal combination of self-pollination and cross-pollination, which often occurs in nature. One of the forms limiting self-pollination is dioeciousness, i.e. on some plants, only male (staminate) flowers develop, and on others, female (pistillate) flowers, having only gynoecium. Monoecious plants have flowers containing both androecium and gynoecium. Another form that limits self-pollination is complete physiological incompatibility. It is expressed in the suppression of the germination of pollen on the stigma of the pistil of the same individual during self-pollination.

There are two types of cross-pollination: biotic and abiotic. Biotic pollination is carried out by animals. Entomophily- pollination by insects; ornithophilia- pollination by birds (hummingbirds). Abiotic pollination occurs with the help of inanimate environmental factors: wind - anemophilia; water near aquatic plants — hydrophilia.

Double fertilization

The pollen, once on the stigma of the pistil, begins to germinate. A pollen tube is formed from a vegetative cell, and two sperm from a generative cell. The pollen tube penetrates into the embryonic sac and, upon reaching the egg, bursts, which ensures the penetration of sperm into it. One sperm copulates with the egg, forming zygote, giving rise to the embryo. The second sperm fuses with a secondary diploid nucleus located in the center of the embryo sac, resulting in the formation of a triploid nucleus. As a result, a triploid cell is formed, which develops into a special nutritive tissue - endosperm(e) (from the Greek. endon- inside, sperma- seed). This is how it happens double fertilization, characteristic only of angiosperms. It was first described in 1898 by the outstanding Russian cytologists embryologist S.G. Navashin. Other cells of the embryo sac - antipodes and synergists - are destroyed.

The biological meaning of double fertilization is that the triploid endosperm develops only in the case of fertilization, which achieves a significant saving of energy and plastic resources, in contrast to gymnosperms, in which the formation of endosperm is not associated with fertilization.

In angiosperms, the endosperm is called secondary, or protein. Only in angiosperms does the embryo (sporophase) begin its development independently due to the triploid phase. In all previous groups (gymnosperms, etc.), the embryo develops due to the gametophase.

So from component parts flowers are formed:

From a fertilized egg - embryo(2n);

Diploid nucleus - endosperm(3p);

Integument ovule - seed coat seed(2n);

Nucellus - seed perisperm(2p);

Ovary wall and often with the participation of other elements of the flower (calyx, receptacle) - the wall of the fruit (pericarp).

The pericarp consists of three layers: outer - exocarp, middle - mesocarp and internal - endocarp.

In many flowering plants (about 10% of species) in the process of evolution, sexual reproduction is replaced by various forms asexual. Of these, the most famous apomixis, in which seeds in apomictic plants are formed without fertilization. In this case, there is no exchange of genetic information; therefore, all apomictic individuals have the same genetic and somatic constitution. Illustrative example plants with apomictic seed formation according to the type of parthenogenesis - dandelion, which is distinguished by its high viability. Often, especially in perennial rhizome plants, vegetative propagation predominates, and seed reproduction is suppressed.

SOCCETES

Inflorescence is called a shoot or a system of specialized shoots bearing flowers. Inflorescences are characteristic of most flowering plants. They have a main axis (inflorescence axis) and lateral axes. The lateral axes may branch or be unbranched and bear flowers. There are nodes and internodes on the axes of the inflorescences. The bracts are located at the nodes of the first-order axes, and the bracts are located at the nodes of the second-order axes.

The biological meaning of inflorescence is the increasing likelihood of pollination of flowers in both entomophilous and anemophilous plants. Undoubtedly, inflorescences are more noticeable among the green leaves than single flowers, and the insect will visit many more flowers per unit of time if they are collected in inflorescences. Usually, the inflorescences are grouped near the top of the plant, at the ends of the branches, but sometimes, especially in tropical trees, they arise on the trunks and thick branches. This phenomenon is known as caulifloria(from the Greek. kaulis- stem and armor. flos- flower). An example is the chocolate tree (Theobroma cacao). It is believed that in a tropical forest, caulifloria makes flowers more accessible to pollinating insects. The presence of inflorescences protects the plant from infertility in the event of the death of a single flower.

Depending on the degree of branching of the axes, simple and complex inflorescences are distinguished. Have simple inflorescences on the main axis single flowers are located (bird cherry, plantain, sunflower); at complex inflorescences- not single flowers, but lateral axes (sweet clover, lilac, wheat, bluegrass). In some plants, the apical meristems are spent on the formation of the apical flower, and in this case the inflorescences are referred to as closed (sympodial), or uncertain. In closed inflorescences, the apical flowers usually open earlier than the underlying lateral ones, and therefore they are called acuminous. In other plants, the apical meristems remain in a vegetative state, and such inflorescences are called open (monopodial), or uncertain. In open inflorescences, flowers bloom sequentially from bottom to top, therefore they are called side-colored.

The classification of inflorescences is rather complicated, but reference books and determinants take into account two features: the nature of branching and the method of growth.

SEE MORE:

Flowering (angiosperms) plants belong to seed plants (along with gymnosperms) and, therefore, sexual reproduction in them is carried out with the help of seeds. Moreover, only in flowering plants during sexual reproduction such a phenomenon as double fertilization is observed. It was discovered in 1898 by the scientist S. Navashin.

The essence of double fertilization is that in flowering plants two sperm are involved in fertilization. One of them fertilizes the egg, resulting in the formation of a zygote. The second sperm fertilizes the so-called central cell, from which storage tissue (endosperm) develops. At the same time, a double set of chromosomes is restored in the zygote, and in the future endosperm - a triple set (which is unique). Below, the process of double fertilization in flowering plants is described in more detail.

In the stamens, in their pollen sacs, pollen grains ripen. Each pollen grain contains two cells: vegetative and generative.

In the ovary of the pistil, an ovule develops (one, several or many, depending on the type of plant). Inside the ovule, as a result of division, eight cells are formed containing a single set of chromosomes (gametophyte). Two of these cells fuse to form a central cell. Another one of these cells becomes the egg.

When a pollen grain hits the stigma of the pistil, the vegetative cell of the grain forms a pollen tube, which grows through the tissues of the pistil and penetrates into the ovule.

For this, there is a special hole in the ovum - a pollen inlet.

The generative cell of the pollen grain divides and forms two sperm. Through the pollen tube, they penetrate into the ovule. One sperm fertilizes an egg, a zygote is formed, containing a double set of chromosomes. The second sperm is fused with the central cell, resulting in a cell with a triple set of chromosomes.

As a result of numerous divisions, the zygote develops into the embryo of a new plant. As a result of the division of the central cell, the endosperm (nutrient tissue for the embryo) is formed. The walls of the ovule become the seed coat. Thus, the ovule becomes a seed.

The pistil ovary is converted into a fruit. Sometimes, not only the ovary, but also other parts of the flower is involved in the formation of the fetus. The fruit is a kind of adaptation of flowering plants to the spread of seeds. The variety of possible distribution methods (using animals, wind, water, self-spreading) gave rise to a huge variety of angiosperm fruits.

Ending. See No. 20, 21, 22/2002

Biology lessons in grade 10 (11)

Appendix 1. Overhead for lesson 6

Appendix 2. Card for working at the board

Appendix 3. Computer testing

"Double fertilization of flowering plants"

Test 1. How many ovules can there be in a pistil?

1. Always alone.
2. Usually equal to the number of seeds.
3. Usually equal to the number of fruits.
4. Equal to the number of pistils.

Test 2. The flower is an organ of asexual and sexual reproduction. What is the manifestation of asexual reproduction?

1. In the formation of seeds.
2. In the formation of fruits.
3. In education controversy.
4. In the formation of gametes.

Test 3. What parts of the flower form the perianth?

1. A calyx of sepals.
2. Corolla of petals.
3. Calyx and corolla.
4. Calyx, corolla, androecium and gynoecium.

Test 4. How is the male gametophyte of flowering plants represented?

1. A set of stamens.
2. A pollen sac.
3. Microspore.
4. Pollen grain.

Test 5. How is the female gametophyte of flowering plants represented?

1. A pestle.
2. Pistil ovary.
3. The ovule.
4. The embryonic sac.

Test 6. What is formed from a fertilized egg?

1. Seed.
2. Fruit.
3. The embryo of the seed.
4. Endosperm.

Test 7. What is formed from a fertilized central cell?

1. Fruit.
2. Seed.
3. The embryo of the seed.
4. Endosperm.

Test 8. What is formed from integuments?

1. Pericarp.
2. Seed peel.
3. Endosperm.
4. Cotyledons.

Test 9. What is the pericarp formed from?

1. From integuments.
2. From the walls of the ovary.
3. From a pestle.
4. From the receptacle.

Test 10. Who Discovered Double Fertilization?

1.S.G. Navashin.
2. I.V. Michurin.
3. N.I. Vavilov.
4. G. Mendel.

Lesson 7. Test for the section "Reproduction and development"

Tasks: to generalize factual material from general biological and evolutionary positions, to check the assimilation of specific factual material, to deepen and expand the knowledge of students.

Demo material: films, students' essays, newspapers, bulletins.

DURING THE CLASSES

Repetition. Written Verification work(30 minutes).

Tests and questions for offset are posted a week in advance. The topics of essays, newspapers are offered.

The test will include the same tests and questions, but in a different order. The teacher distributes leaflets with questions to each table, the class is divided into two options, each option is offered 10 tests (1-10, 11-20, 21-30, 31-40) and one theoretical question. The next class will have other tests and other theoretical questions.

Test questions

Option 1

1. What is the name of the set of chromosomes characteristic of a species?
2. What is the set of chromosomes in somatic and germ cells?
3. How many chromosomes and DNA are in different periods of the interphase?
4. What are the paired, identical chromosomes of a somatic cell called?
5. What are the primary constriction and ends of the chromosome called?
6. How many chromosomes and DNA are in a cell before mitosis and at the end of mitosis?
7. How many chromosomes and DNA are in prophase, metaphase and anaphase of mitosis?
8. What is the meaning of meiosis?
9. What are the first and second divisions of meiosis called?
10. What processes take place in the cell in prophase I of meiosis?
11. How many chromosomes and DNA are there before meiosis, after the first and second divisions?
12. What is the set of chromosomes and DNA in metaphase I and anaphase I of meiosis?


15. When does recombination of genetic material occur in meiosis?
16. List the phases of meiosis during which the chromosomes are dichromatid.

18. What is the name of the division, in which multiple nuclear fission occurs and several individuals are formed (in trypanosomes, malaria plasmodium)?
19. What is characteristic of the genotypes of daughter individuals in comparison with the mother during asexual reproduction?
20. What set of chromosomes do spores have?
21. What is the name of the membrane of the mammalian ovum?
22. When does oogenesis begin in humans?
23. What is the name of reproduction, in which the development of a new organism occurs from an unfertilized egg?
24. What is the set of chromosomes of gametogonia, 1st order gametocytes, 2nd order gametocytes?
25. What is formed after spermatogenesis from one spermatocyte?
26. What is formed after oogenesis from one oocyte?
27. What organisms have external fertilization?
28. What are the male and female gametophytes of flowering plants?
29. What is formed from the integuments and the central cell of the embryo sac?
30. What is the pericarp formed from?
31. Who Discovered Double Fertilization?
32. From what periods does the ontogenesis of animals develop?
33. From what periods does animal embryogenesis develop?
34. What is formed as a result of zygote crushing?
35. What is the name of a two-layer embryo of a lancelet?
36. What is formed from the ectoderm, endoderm and mesoderm of the neurula?
37. From which germ layers are formed the spine, epidermis and lungs?
38. What animals are deuterostomes?
39. Name three animals with direct postembryonic development.
40. Name three animals with indirect postembryonic development.

Theoretical questions

1. The mitotic cycle of the cell.
2. Draw and explain the behavior of a pair of homologous chromosomes in prophase, metaphase, anaphase and telophase of the first meiotic division.

Option 2

1. What is formed after spermatogenesis from one spermatocyte?
2. What animals are deuterostomes?
3. What is formed from the integuments and the central cell of the embryo sac?
4. What is the name of the set of chromosomes characteristic of the species?
5. How many chromosomes and DNA are there in different periods of the interphase?
6. How many chromosomes and DNA are in prophase, metaphase and anaphase of mitosis?
7. What is the name of a two-layer embryo of a lancelet?
8. What is the meaning of meiosis?
9. What processes take place in a cell in prophase I of meiosis?
10. How many chromosomes and DNA are there before meiosis, after the first and second division?
11. What is the set of chromosomes and DNA in metaphase I and anaphase I of meiosis?
12. What is the pericarp formed from?
13. What is characteristic of the interphase between the first and second divisions of meiosis?
14. What is the set of chromosomes and DNA in metaphase II and anaphase II of meiosis?
15. What is formed after oogenesis from one oocyte?
16. What are the paired, identical chromosomes of a somatic cell called?
17. What is characteristic of asexual reproduction?
18. From what periods does animal embryogenesis develop?
19. How many chromosomes and DNA are in a cell before mitosis and at the end of mitosis?
20. What is the name of the division, in which multiple nuclear fission occurs and several individuals are formed (in trypanosomes, malaria plasmodium)?
21. What is characteristic of the genotypes of daughter individuals in comparison with the mother during asexual reproduction?
22. What germ layers form the spine, epidermis and lungs?
23. What set of chromosomes do spores have?
24. What is the name of the membrane of the mammalian ovum?
25. What are the names of the primary constriction and ends of the chromosome?
26. When does oogenesis begin in humans?
27. Name three animals with indirect postembryonic development.
28. What is the name of reproduction, in which the development of a new organism occurs from an unfertilized egg?
29. What is the set of chromosomes of gametogonia, gametocytes of the 1st order, gametocytes of the 2nd order?
30. What is the set of chromosomes in somatic and germ cells?
31. What organisms have external fertilization?
32. What are the male and female gametophytes of flowering plants?
33. Who discovered double fertilization?
34. From what periods does the ontogenesis of animals develop?
35. List the phases of meiosis during which the chromosomes are dichromatid.
36. What is formed as a result of zygote crushing?
37. What are the first and second divisions of meiosis called?
38. What is formed from the ectoderm, endoderm and mesoderm of the neurula?
39. When does recombination of genetic material occur in meiosis?
40. Name three animals with direct postembryonic development.

Theoretical questions

1. The mitotic cycle of the cell.
2. Draw and explain the behavior of a pair of homologous chromosomes in prophase, metaphase, anaphase and telophase of the first meiotic division.
3. Asexual reproduction and its forms.
4. Eggs, sperm. Gametogenesis.
5. Types of ontogenesis. Stages of embryogenesis.
6. Formation of spores and gametes in flowering plants. Double fertilization.

Watching films, listening to abstracts in order to deepen knowledge on this section (10 min).

Topics for essays:“Natural and artificial parthenogenesis”, “Cloning”, “Hermaphroditism”, “The role of hormones in the life of organisms”, “Aging and immortality”.

Answers to tasks

Assignment on the topic "Mitosis". Test 1. 2. Test 2. 1. Test 3. 3. Test 4. 2. Test 5. 2. Test 6. 3. * Test 7. 1, 2. Test 8. 3. Test 9. 3. * Test 10. 2, 3, 4, 5.

Assignment on the topic "Meiosis". Test 1. 1. Test 2. 2. Test 3. 1. * Test 4. 1, 2, 3. Test 5. 7. * Test 6. 4, 5, 6. Test 7. 8, Test 8. 8. * Test 9. 1, 3, 7. Test 10. 1.

Assignment on the topic "Asexual and Sexual Reproduction." Test 1. 8. Test 2. 4. Test 3. 6. Test 4. 7. Test 5. 3. * Test 6. 1, 3. Test 7. 2. * Test 8. 2, 3, 4. * Test 9. 1, 2, 3. Test 10. 4.

Assignment on the topic “Gametogenesis. Fertilization". Test 1. 1. Test 2. 3. Test 3. 4. Test 4. 1. Test 5. 4. Test 6. 1. Test 7. 3. Test 8. 2. * Test 9. 1, 2. * Test 10. 1, 2, 3.

Assignment on the topic "Double fertilization of flowering plants." Test 1. 2. Test 2. 3. Test 3. 3. Test 4. 1. Test 5. 4. Test 6. 3. Test 7. 4. Test 8. 2. Test 9. 2. Test 10. 1.

James Dewey Watson is an American specialist in molecular biology, geneticist and zoologist; best known for his participation in the discovery of the structure of DNA in 1953. Winner of the Nobel Prize in Physiology or Medicine.

After successful completion The University of Chicago and Indiana University Watson spent some time doing chemistry research with biochemist Herman Kalckar in Copenhagen. He later moved to Cavendish's laboratory at the University of Cambridge, where he first met his future colleague and comrade Francis Crick.

Watson and Crick came up with the idea of ​​a DNA double helix in mid-March 1953, studying experimental data collected by Rosalind Franklin and Maurice Wilkins. The discovery was announced by Sir Lawrence Bragg, director of Cavendish's laboratory; this happened at a Belgian scientific conference on April 8, 1953. However, the press did not actually notice an important statement. On April 25, 1953, an article about the discovery was published in scientific journal"Nature". Other biologists and whole line Nobel laureates quickly appreciated the monumentality of the discovery; some even called it the greatest scientific discovery 20th century.

In 1962, Watson, Crick and Wilkins received the Nobel Prize in Physiology or Medicine for their discovery. The fourth participant in the project, Rosalind Franklin, died in 1958 and, as a result, could no longer apply for the award. Watson also received a monument at the American Museum of Natural History in New York for his discovery; since such monuments are erected only in honor of American scientists, Crick and Wilkins were left without monuments.

Watson is considered to this day one of the greatest scientists in history; however, as a person, many openly disliked him. James Watson several times became a defendant in rather high-profile scandals; one of them was directly related to his work - the fact is that during the work on the DNA model, Watson and Crick used the data obtained by Rosalind Franklin without her permission. With Franklin's partner, Wilkins, the scientists worked quite actively; Rosalind herself, quite possibly, until the end of her life, and may not have known how important her experiments played in understanding the structure of DNA.

From 1956 to 1976, Watson worked in the Harvard Department of Biology; during this period he was mainly interested in molecular biology.

In 1968, Watson was appointed director of the Cold Spring Harbor laboratory in Long Island, New York (Long Island, New York); through his efforts in the laboratory, the level of quality has risen considerably research work and funding has improved markedly. Watson himself during this period was primarily engaged in cancer research; along the way, he made the laboratory under his control one of the best centers of molecular biology in the world.

In 1994, Watson became president research center, in 2004 - rector; in 2007, he left his post after rather unpopular statements about the existence of a connection between the level of intelligence and origin.

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