What are the sex chromosomes in a chicken. Are humans as close to chickens as they are to chimpanzees? About hens and roosters
At present, no one doubts that the sex chromosomes determine the initial determination of sex.
However, the mechanism of their action and even the general picture of the chromosomal apparatus have not yet been sufficiently studied. There is no consensus on the number of chromosomes even in such a well-studied species as the domestic chicken. Matti reports that the chromosomes of birds are the least studied of all classes of vertebrates due to the large number of chromosomes in birds and their small size. The author cites the following literature data on the number of chromosomes in a chicken: 28, 32, 36, 66, 74 and 78. Matti considers the last number to be correct, and there are only 12 large chromosomes. Apparently, Nyokamer, Donelly and Farbs, considering that chickens have 5 pairs of somatic and 1 pair of sex chromosomes, only these large chromosomes are taken into account. Matti also gives data on the number of chromosomes in a number of bird species: Oceanodroma lencorrhoa - 74, Phalacrocorax carbo - 70, Sternula albifrons - 66, Larus argentatus - 66, Brachyramhus marmoratus - 50, Lunda cirrhata - 50, Anas platyrhynchos - 80 and Coturnix coturnix - 78. Jaff and Feckheimer found that chickens, turkeys and quails have 70-80 chromosomes and emphasize that the number of chromosomes for each species is constant.
All of these chromosomes, except for one pair, are somatic. The male germ cells contain one pair of sex chromosomes, which, according to various researchers, is either the first or fifth pair, and according to the latest data, the 4-5th pair. The question of whether female birds have one sex X chromosome or one X chromosome and one Y chromosome has not yet been resolved. In any case, it is clear that the sex in birds is determined by the female (in mammals, by the male), since her gametes are different (heterogametic type): half contains the X chromosome, and half either the Y chromosome or does not contain sex chromosomes at all, in while all male gametes always contain one X chromosome (homogametic type). Even in latest research there are controversies on this issue. Jaff and Feckheimer believe that female birds have only one sex chromosome, and Bamney et al convincingly prove the presence of a second chromosome in female chickens, turkeys and quails (which the authors call the W chromosome), located quite far from the first (which the authors call Z -chromosome) and having 8-10 times smaller size. This picture, as noted by the authors, differs from what occurs in the heterogametic sex of mammals (in males). In male birds, according to the authors, two sex chromosomes are interconnected, making up, as it were, one chromosome.
Benois believes that the X chromosome contains the "male factor - M", and in the gamete without sex chromosomes - the "female factor - F". Therefore, at fertilization, zygotes are obtained either FMM (providing an advantage M and causing a male) or FFMM (an advantage F - female). The author comes to the conclusion that this genetic advantage automatically orients the development of the gonad to the testis or ovary, being the first agent of sexual differentiation. Developing this position, Newcamer, Donelly and Farbs believe that the main factor determining the determination of sex is the ratio between somatic and sex chromosomes.
Let us now consider how the researchers imagine the realization of gene potencies during sex differentiation. One of the first noted the dominance of the female sex hormone Danchakova. When a female hormone is administered to genetically male individuals, according to the colorful expression of the author, "the genetic constitution of the male chromosomes of germ cells and somatic tissues is powerless to resist the energetic stimulus of the hormone, which introduces antagonistic reactions of the dominant sex - the female." Discussing the role of the gene mechanism and sex hormones in sex differentiation, Villiers, Galager and Koch believe that the male zygote in chicken embryos contains genetic factors of both sexes and that the primary factor in determining the male sex of the embryo is the dominance of male genetic factors over female ones; the intersex state should be considered an intensification of the female factors of the male zygote by injected female sex hormones. The authors note a surprising similarity between the action of genes and hormones in the determinism of the sex of the embryo. Considering that the cortex and medulla of the gonads have an opposite sexual tendency, Benoit argues that the chemicals released by genes from the very beginning of gonadal development determine the development of the cortex or medulla in the gonad. However, the author does not specify either the chemical nature of these substances, or whether they are identical to hormones, as Volf believes, or not. Domm believes that genes determine the intensity of hormonal secretion and that the gonadal component (cortex or medulla), which has a greater intensity of secretion, determines sex. Due to the fact that amphibians, unlike birds, have a heterogamous male sex, they have a more effective male hormone, while birds have a female one. Therefore, the author believes that the differentiation of sexes in birds is determined by female hormone, and the male is present in both sexes, but is suppressed by the female. The author comes to the conclusion that the heterogametic sex has a bisexual hormonal potential, i.e. female birds are capable of producing both female and male hormones. In some cyclostomes, bisexuality persists into adulthood, but in most vertebrates, hermaphroditism is an anomaly. Villiers and Weniger come to a similar conclusion that genes control the amount of hormones produced, and they in turn determine sex determination. Burns expresses the opposite opinion. The author believes that primary germ cells do not affect either the histological structure of the gonads or sex determination. According to the author, the sex of the gonad is determined by the structural elements of the gonad-forming site, regardless of the genetic constitution of the included primary germ cells, which are indifferent or bipotential even in relation to the formation of gametes.
Let us present several experimental works that help to clarify the role of individual components of the gonad in sex determination. Huffen found that the female germinal epithelium always differentiates into the ovarian cortex, regardless of whether it developed with the female or male medulla. The germinal epithelium of the male, taken before sexual differentiation (5-6th day of incubation), is influenced by the tissue with which it is in contact. So, the author's data show that the cortex of the gonads of the male and the gonads of the female are not equivalent. Consequently, the concepts of Benoit and Burns, giving great importance in determining sex, which component of the gonad (cortex or medulla) dominates in development are incorrect. Based on the results of experiments on the injection of male and female sex hormones, Hamilton comes to the conclusion that the normal, sex-specific form of regression of the Mullerian channels (from the 5th to 6th day - the beginning of differentiation of the genitourinary system, to the 8th to 9th day - the beginning channel regression) occurs due to hormone stimulation of unknown, genetically determined intracellular receptors and that the programmed involution of Müllerian channels is caused by the suppression of oxidative processes and the release of proteolytic and hydrolytic enzymes characteristic of tissue undergoing degeneration.
Based on the fact that the reshaping of the female sex with the introduction of androgenic hormones fails, but with heterosexual parabiosis or implantation in female testicles is successful, Vici and Dale suggest that animals form dioecious species of substances, similar to antibodies, which antagonize or completely suppress the development of the sex glands of the opposite sex. kind.
Faber indirectly showed the connection between gonadotropic hormone and sex determination, refuting Villiers' opinion about the absence of this connection. Summarizing his observations on a number of bird species (muscovy ducks, domestic ducks, hybrids between them, hawks), the author found that in the sex with a greater weight and body size, acidophilic cells of a larger size were observed in the pituitary gland.
1 . Unlike DNA molecules, protein molecules contain atoms:
a) sulfur;
b) hydrogen;
c) nitrogen;
d) protein and DNA molecules contain the same atoms.
2 . Mutations occur as a result of changes in:
a) DNA;
b) cellular structures;
c) metabolism;
d) protein.
3 . If we take ribosomes and enzymes from bacteria, ATP and ADP and amino acids from a fungus, DNA from a lizard for protein synthesis, then proteins will be synthesized:
a) a fungus
b) lizards;
c) bacteria;
d) all three organisms.
4 . A living system corresponding to the biomolecular level of organization of living matter:
a) plant chloroplast
b) mammalian egg;
c) influenza virus;
d) there are no such living systems on Earth at all.
5 . The chemical element that is required integral part hemoglobin protein in mammals:
a) zinc;
b) copper;
c) chlorine;
d) iron.
6 . For a quick recovery from fatigue during the preparation for the exam, it is better to eat:
a) an apple
b) a piece of sugar;
c) a sandwich;
d) a piece of meat.
7 . A plant cell, unlike an animal cell, contains:
a) ribosomes;
b) vacuoles, plastids and cellulose membrane;
c) reserve nutrients;
d) more chromosomes in the nucleus.
8 . All of the following organisms are prokaryotes:
a) bacteria, yeast, blue-green algae;
b) bacteria, blue-green algae;
c) yeast, bacteria;
d) viruses and bacteria.
9 . All of the following organisms have cell nuclei:
a) parrot, fly agaric, birch;
b) cat, nitrogen-fixing bacteria;
c) Escherichia coli, roundworm;
d) roundworm, AIDS virus, octopus.
10 . Of the listed cells, there are more mitochondria in:
a) egg cells of birds;
b) mammalian erythrocytes;
c) mammalian spermatozoa;
d) green plant cells.
11 . The chemical reactions of anabolism predominate in cells:
a) plants;
b) mushrooms;
c) animals;
d) the level of anabolism is the same for everyone.
12 . The following cells take part in sexual reproduction in multicellular organisms:
a) disputes;
b) eggs and sperm;
c) somatic;
d) different, depending on the circumstances.
13 . The cell cycle is:
a) the totality and order of all chemical reactions in the cell;
b) cell life from division to division;
c) cell life from division to division plus the time of division itself;
d) the time when the cell is preparing to divide.
14 . The somatic cell of a diploid organism before entering the stage of mitosis has a set of chromosomes:
a) diploid (2 n);
b) haploid ( n);
c) tetraploid (4 n);
d) depending on the circumstances.
15 . The set of chromosomes is haploid in:
a) chicken egg
b) wheat seed cells;
c) human leukocytes;
d) covering cells of higher plants.
16 . Reproduction methods, characteristic only for plants:
a) seeds, mustaches, spores;
b) bulb, mustache, layering;
c) seeds, layering, spores;
d) cell division, bulb, mustache.
17 . Advantages of sexual reproduction over asexual reproduction:
a) the simplicity of the process;
b) the complexity of the process;
c) in greater genetic diversity of individuals of the next generation;
d) in accelerating the growth of the species.
18 . The stage of meiosis and the reason why mutations can occur in the germ cell:
a) as a result of crossing over in prophase I;
b) as a result of incorrect divergence of chromosomes in telophase I or II;
c) as a result of radiation exposure of the body during the formation of germ cells;
d) for any of the above reasons.
19 . The group of living systems representing organism level organizations:
a) apple tree, apple, codling moth caterpillar;
b) apple tree, earthworm, apple flower;
c) apple tree, earthworm, caterpillar;
d) apple, caterpillar, earthworm.
20 . Correct sequence initial stages ontogeny:
a) zygote, gastrula, blastula;
b) fertilization, gastrula, blastula;
c) gametogenesis, fertilization, blastula, gastrula;
d) None of the answers are correct.
21 . Fertilization in the female body in humans normally occurs:
a) in the uterus;
b) in the upper part of the fallopian tubes;
c) in the vagina;
d) in the ovaries.
22 . For the conception of two identical twins, fertilization is necessary:
a) one egg by two spermatozoa;
b) two eggs with one sperm;
c) two eggs and two spermatozoa;
d) one egg with one sperm.
23 . More heterozygous individuals will be obtained from crossing:
a) AABB ґ aaBB;
b) AAbb ґ aaBB;
in) AaBb ґ AaBb;
G) aabb ґ Aabb.
24 . The set of sex chromosomes is normal in a rooster:
a) XO;
b) XXY;
c) XX;
d) XY.
25 . If parents have I and IV blood groups, then children may have blood types:
a) only I;
b) only IV;
c) only II or III;
d) only I or IV.
26 . For the first time, he discovered and described the fundamental laws of gene distribution in offspring when crossing hybrids:
a) J.-B. Lamarck;
b) G. Mendel;
c) C. Darwin;
d) N.I. Vavilov.
27 . The unit of evolution is:
a) an individual;
b) view;
c) population;
d) ecosystem.
28 . An example of non-hereditary variability is:
a) the appearance of an albino in the offspring of a lion pride;
b) an increase in the percentage of fat content of milk in cows with a change in the composition and mode of feeding;
c) an increase in the percentage of fat content of milk in cows of a highly productive breed;
d) loss of vision in a mole as a result of evolution.
29 . The factor determining the direction of evolution is:
a) isolation;
b) mutation;
c) natural selection;
d) population fluctuations.
30 . An example of aromorphosis is:
a) the appearance of pulmonary respiration in amphibians;
b) flat body shape in demersal fish;
c) lack of color in cave animals;
d) the presence of thorns and spines in the fruits of plants.
31 . The presence of microbes in the environment of the body is:
a) abiotic environmental factor;
b) biotic environmental factor;
c) anthropogenic factor;
d) limiting factor.
32. An example of biogeocenosis is:
a) a pond with all the inhabitants;
b) an aquarium;
c) all living inhabitants of the pond;
d) all representatives of the pond flora.
33. The brown bear in the natural ecosystem acts as a consumer of the third order when it eats:
a) berries
b) pike;
c) wild boar;
d) bulbs of herbaceous plants.
34 . The signal for the start of migration in migratory birds is:
a) the onset of cold weather;
b) the age of the chicks;
c) change in the length of the day;
d) lack of food.
35 . An integral component of all natural ecosystems are:
a) fungi and bacteria;
b) herbivores;
c) carnivorous animals;
d) insects.
36 . In the food chain grass - grasshoppers - lizards - owls for the existence of a pair of owls with a total weight of 5 kg, grass is needed:
a) 50 tons;
b) 5 tons;
c) 500 kg;
d) 2.5 tons.
37 . Specify which types of competition may arise between:
a) man and cockroaches;
b) hawk and wolf;
c) elk and mouse;
d) mustang and bison.
38 . The relationship between humans and E. coli is an example:
39. gas function living matter on Earth is carried out:
a) only plants
b) plants and some bacteria;
c) plants, bacteria and animals;
d) all living beings.
40. "On the earth's surface there is no chemical force more constantly active, and therefore more powerful in its final consequences, than living organisms taken as a whole. These words belong to:
a) N.I. Vavilov;
b) V.I. Vernadsky;
c) D.I. Mendeleev;
d) K.E. Tsiolkovsky.
Answers.
1 - a. 2 - a. 3 – b. 4 - in. 5 - G. 6 – b. 7 – b. 8 – b. 9 - a. 10 - in. 11 - a. 12 – b. 13 - in. 14 - a. 15 - a. 16 - b. 17 - in. 18 - G. 19 - in. 20 - G. 21 - b. 22 - G. 23 – b. 24 - in. 25 - in. 26 - b. 27 - in. 28 – b. 29 - in. 30 - a. 31 - b. 32 - a. 33 – b. 34 - in. 35 - a. 36 - b. 37 - G. 38 - G. 39 - G. 40 – b.
Sample tasks from examination work in biology for the 11th grade
The human Y chromosome is as different from the chimpanzee Y chromosome as it is from the chicken chromosome.
Brian Thomas, M.S.*
In a recent comprehensive study, scientists compared the human Y chromosome with the chimpanzee Y chromosome and found that they "surprisingly different" .
@ Jeff Johnson www.mbbnet.umn.edu
The Y chromosome is present only in males and contains genes that determine male signs. In addition, this chromosome contains genetic and regulatory information that is used throughout the body. In a study published in the January issue of the journal Nature, a group of scientists suddenly encountered such a huge number of unexpected differences in DNA sequences on human and chimpanzee Y chromosomes that it took much longer than originally planned. Among other things, the researchers found interesting features, characteristic of certain "classes of sequences" within each chromosome.
Most of the data obtained during the study are not consistent with popular misstatement, according to which the similarity between humans and chimpanzees is 98%. In addition, these data contradict another, even more common hypothesis, which suggests that humans and chimpanzees have a common ancestor. One class of sequences within the chimpanzee Y chromosome was less than 10% similar to a similar class of sequences on the human Y chromosome and vice versa. Another large class was only half similar to a similar class of another species and vice versa. And one class of sequences in the human Y chromosome in general "had no counterpart on the chimpanzee Y chromosome" .
If evolutionary assumptions of long-term gradual genetic change are to be followed, Y-chromosome structures, alignments, genes, and other sequences should be virtually identical in both species. This similarity should be especially clear when considering the relatively short (according to the evolutionary time scale) period of 6 million years when chimpanzees and humans supposedly diverged from a common ancestor. However, the data obtained indicate significant differences between chromosomes. R. Scott Hawley, a research geneticist at the Stower Institute in Kansas City who was not involved in the study, told The Associated Press: “The results of the study are simply amazing” .
In one of the magazine articles Nature The discrepancy between these data and standard evolutionary interpretations has been commented on rather reservedly: “In fact, the Y-chromosome genes of humans and chimpanzees, which diverged 6 million years ago, differ as much as the autosomal genes of humans and chickens, whose common ancestors lived on Earth 310 million years ago.”. Autosomes are all chromosomes except for the X and Y sex chromosomes.
So, the human Y chromosome is different from the chimpanzee Y chromosome. as strong as from chicken chromosomes. And in order to explain where all these differences between humans and chimpanzees come from, supporters of large-scale evolution are forced to invent stories about rapid overall rearrangements and the rapid formation of DNA containing new genes, as well as regulatory DNA.
But since each respective Y chromosome is single and completely dependent on the host organism, it is most logical to assume that humans and chimpanzees were created in a special way - separately, as completely different creatures.
Links and notes
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How many chromosomes do roosters and chickens have, you will learn from this article.
How many chromosomes do a rooster and a hen have?
After numerous studies, scientists have found that the body of a rooster and a chicken contains the same number of chromosomes - 78 units.
The rooster is a male chicken, a male of the galliform family. They are distinguished from females by a large crest, earrings and a magnificent, multi-colored tail plumage.
Interestingly, in birds, unlike humans, gender is not determined by the XX set ( female body) or XY ( male body), while ZZ and ZW are sets, respectively. Also, only in chickens, the cells of their body know their future sex even before the chicks are born. Scientists are at a loss what kind of sex determination system they have, because they have not encountered one before. Thus, the cells of the bird themselves determine it. They do not obey the commands produced by the sex glands, but lead their own internal routine.
What are chromosomes?
Chromosomes is the genetic material found in a cell of an organism. Each of them contains a DNA molecule in a twisted helix. Full set chromosome is called a karyotype. Each chromosome is a complex of proteins and DNA. And all types of living organisms have their own, permanent and different from the rest of the chromosome species set.
The appearance of a chromosome resembles a long thread with hundreds of beads strung on it. Each of them is a genome. In addition, the beads have their own strictly fixed place on the chromosome, called a locus, and it controls a single trait or a whole group of traits of an individual.