Name: y chromosome structure and male traits
Uploaded: 2021-04-07T12:11:58.000Z
Duration: 2 min 19 s
Channel: JoVE

K12 Standards

Louisiana Student Standards for Science

High School

Life Sciences

heredity-inheritance-and-variation-of-traits

Heredity: Inheritance And Variation Of Traits

HS-LS3-2

The Y Chromosome Determines Maleness

Il y a deux chromosomes sexuels chez l’homme : X et Y.
Le chromosome Y détermine le sexe masculin et est le plus petit chromosome du génome humain.
Il y a trois régions dans le chromosome Y : la partie pseudoautosomique, qui est elle-même divisée en deux régions - PAR1 et PAR2, la région hétérochromatique et la région euchromatique.
Le gène S-R-Y est situé dans la région euchromatique du chromosome Y. Il joue un rôle essentiel dans le développement des fœtus masculins.
Lorsqu’un ovule portant un chromosome X fusionne avec un spermatozoïde porteur d’un chromosome Y, il forme un zygote.
Le zygote se divise ensuite continuellement pour former un embryon. À ce stade, les embryons mâles et femelles se développent le long de la même voie et sont physiologiquement identiques.
Au cours des premiers stades de développement, l’embryon possède deux organes précurseurs : le canal wolffien et le canal müllérien.
Le canal wolffien peut se différencier en structures génitales masculines et le canal müllérien peut se différencier en structures génitales féminines.
Dans les semaines qui suivent la fécondation, le gène S-R-Y présent sur le chromosome Y est transcrit puis traduit en protéine S-R-Y. La protéine S-R-Y initie le développement des testicules chez le fœtus.
 La protéine S-R-Y agit comme un facteur transcriptionnel et se lie à des sites spécifiques de l’ADN, activant ainsi la voie de formation des testicules.
Ensuite, les gonades commencent à sécréter plusieurs hormones, dont l’hormone anti-müllérienne et la testostérone.
L’hormone anti-müllérienne inhibe le développement du canal müllérien.
La testostérone, quant à elle, initie le développement du canal de Wolffi en canaux déférents, canaux éjaculateurs et vésicules séminales.
Si cette voie est perturbée et que les gonades ne parviennent pas à sécréter de testostérone et d’hormone anti-müllérienne, le canal müllérien se développe en organes reproducteurs féminins même si le fœtus est génotypiquement XY.

<ol>
	<li>Willard, Huntington F. « Contes du chromosome Y. » Nature 423, n° 6942 (2003) : 811-813.</li>
	<li>Ginalski, Krzysztof, Leszek Rychlewski, David Baker et Nick V. Grishin. « Prédiction de la structure des protéines pour la région spécifique à l’homme du chromosome Y humain. » Actes de l’Académie nationale des sciences 101, n° 8 (2004) : 2305-2310.</li>
	<li>Noordam, Michiel J., et Sjoerd Repping. « Le chromosome Y humain : un chromosome masculin. » Opinion actuelle en génétique et développement 16, n° 3 (2006) : 225-232.</li>
</ol>

le chromosome y détermine la masculinité

Le chromosome Y est un chromosome sexuel présent chez plusieurs vertébrés et mammifères, dont les humains. En plus de 22 paires d’autosomes, les mâles humains possèdent un chromosome X et un chromosome Y. Chez ces organismes, la présence ou l’absence du chromosome Y détermine le développement des traits masculins.

Évolution

Il y a environ 300 millions d’années, les deux chromosomes sexuels divergeaient de deux chromosomes autosomiques identiques. Au fil du temps, le chromosome Y a perdu la plupart de ses gènes et sa taille a diminué. Aujourd’hui, seule une petite partie du chromosome Y partage une séquence similaire avec le chromosome X. Une vaste étude scientifique sur les chromosomes Y chez huit mammifères, dont des singes, des souris, des rats, des taureaux, des opossums, des chimpanzés et des humains, a montré 18 régions très similaires sur les chromosomes Y. Le fait que ces régions soient conservées chez tous ces mammifères, malgré la perte d’une grande partie des chromosomes Y au cours de l’évolution, montre que les gènes présents sur les chromosomes Y sont vitaux pour la survie de ces mammifères.

Structure

Le chromosome Y des mammifères comporte trois régions principales. Les régions pseudoautosomiques du chromosome Y partagent une homologie avec le chromosome X et peuvent subir une recombinaison méiotique. Ainsi, les gènes présents dans les régions pseudoautosomiques sont hérités de manière autosomique plutôt que liée au sexe. La deuxième région est une région euchromatine désignée comme région du chromosome Y spécifique au mâle ou MSY. Il s'étend sur 23 Mo et possède peu de gènes codant pour des protéines, tels que le gène SRY, un régulateur principal de la masculinité et le gène ZFY requis pour la spermatogenèse. La troisième région est une région hétérochromatine qui contient plusieurs séquences répétitives.

Mutations et leurs effets

Les délétions dans la région MSY du chromosome Y affectent le développement des spermatozoïdes et provoquent la stérilité masculine. Par exemple, les délétions du gène AZF sur le bras long du chromosome Y conduisent à une affection appelée azoospermie, dans laquelle les spermatozoïdes ne se trouvent pas dans l'éjaculat masculin. De plus, des délétions dans des régions spécifiques de MSY sont associées à des tumeurs des cellules germinales testiculaires (TGCT).

Le chromosome Y détermine la masculinité

Le chromosome Y est un chromosome sexuel présent chez plusieurs vertébrés et mammifères, y compris les humains. En plus des 22 paires d’autosomes, l’homme ...

Education

Enseignement

JoVE Core

Molecular Biology

Biologie moléculaire

Unit 2

Unité 2

Mendelian Genetics

La génétique mendélienne

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

y chromosome structure and male traits

The Y chromosome is a sex chromosome that helps guide male development in humans and other vertebrates and mammals. Human males usually have one X chromosome and one Y chromosome, along with 22 pairs of autosomes. In these organisms, the presence or absence of the Y chromosome influences whether male traits develop.

The Y chromosome evolved from an autosome about 300 million years ago, when two sex chromosomes began to diverge. Since then, it has lost most of its genes and become much smaller. Only a small region still shares sequence similarity with the X chromosome. A large study of Y chromosomes in eight mammals, including monkeys, mice, rats, bulls, opossums, chimpanzees, and humans, found 18 highly similar regions. Their long-term retention suggests that Y-linked genes remain important for mammalian survival.

The mammalian Y chromosome has three main regions. The pseudoautosomal regions match parts of the X chromosome and can undergo meiotic recombination, which means they can be inherited more like autosomes than sex-linked genes. The second region is the male-specific Y chromosome region, or MSY. It is a euchromatin region about 23 Mb long and contains few protein-coding genes, including SRY, a master regulator of maleness, and ZFY, which is required for spermatogenesis. The third region is heterochromatin, which contains many repetitive sequences.

Changes in the MSY region can have major effects on reproduction. Deletions in this region can disrupt sperm development and lead to male sterility. For example, deletions in the AZF gene on the long arm of the Y chromosome can cause azoospermia, a condition in which spermatozoa are not found in the male ejaculate. Deletions in specific MSY regions are also linked to testicular germ cell tumors, or TGCTs.

Y Chromosome Structure and Male Traits

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the y chromosome determines maleness

The Y chromosome is a sex chromosome that helps guide male development in humans and other vertebrates and mammals. Human males usually have one X chromosome and one Y chromosome, along with 22 pairs of autosomes. In these organisms, the presence or absence of the Y chromosome influences whether male traits develop. The Y chromosome evolved from an autosome about 300 million years ago, when two sex chromosomes began to diverge. Since then, it has lost most of its genes and become much smaller.

the ratio of x chromosome to autosomes

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key terms and concepts

Explore how the Y chromosome evolved, how its three regions differ, and how MSY deletions can affect sperm development and male fertility.

Y Chromosome Structure and Male Traits | JoVE K12

molecular biology

JoVE Core Biologie Moléculaire illustre les processus moléculaires au sein de la cellule grâce à des leçons vidéos claires et concises. Les applications de ces concepts sont ensuite démontrées grâce à des expériences concrètes en laboratoire.

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Ohio’s Learning Standards and Model Curriculum

9-12

Biology

Heredity

Genetic mechanisms and inheritance

Tennessee Academic Standards

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Links Among Engineering, Technology, Science, and Society

BIO1.ETS2.2

Alabama Course of Study Science

Heredity: Inheritance and Variation of Traits

9-12.B.3.11.a

Next Generation Science Standards

Life Science

HS-LS3-1

Texas Essential Knowledge and Skills

BIO.8

BIO.8.B

new-york-state-science-learning-standards

New York State Science Learning Standards

Inheritance and Variation of Traits

HS-LS3-1.

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Formulate, refine, and evaluate questions to clarify relationships about the role of DNA and chromosomes in coding the instructions for characteristic traits passed from parents to offspring. Emphasis should be on traits including completely dominant, codominant, incompletely dominant, and sex-linked traits (e.g., pedigrees, karyotypes, genetic disorders, Punnett squares). Examples do not need to include dihybrid crosses.

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Y Chromosome Structure and Male Traits

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