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

人間には、XとYの2つの性染色体があります。
Y染色体は男性の性別を決定し、ヒトゲノムの最小染色体です。
Y染色体には3つの領域があります:偽常染色体部分は、さらにPAR1とPAR2の2つの領域、ヘテロクロマティック領域、およびユークロマティック領域に分けられます。
S-R-Y遺伝子は、Y染色体のユークロマティック領域に位置しています。それは男性の胎児の発達に重要な役割を果たします。
X染色体を持つ卵子がY染色体を持つ精子と融合すると、受精卵が形成されます。
その後、受精卵は連続的に分裂して胚を形成します。この段階では、男性と女性の胚は同じ経路に沿って発生しており、生理学的に同一です。
発生の初期段階では、胚にはウォルフ管とミュラー管の2つの前駆器官があります。
ウォルフ管は男性の生殖器構造に分化することができ、ミュラー管は女性の生殖器構造に分化することができます。
受精後数週間で、Y染色体上に存在するS-R-Y遺伝子が転写され、次にS-R-Yタンパク質に翻訳されます。S-R-Yタンパク質は、胎児の精巣の発達を開始します。
 S-R-Yタンパク質は転写因子として作用し、DNA上の特定の部位に結合するため、精巣形成経路が活性化されます。
その後、生殖腺は抗ミュラー管ホルモンやテストステロンなど、いくつかのホルモンを分泌し始めます。
抗ミュラー管ホルモンは、ミュラー管の発達を阻害します。
一方、テストステロンは、ウォルフ管が輸精管、射精管、精嚢に発達するのを開始します。
この経路が破壊され、生殖腺がテストステロンと抗ミュラー管ホルモンを分泌できなくなった場合、胎児が遺伝子型がXYであっても、ミュラー管は女性の生殖器官に発達します。

<ol>
	<li>ウィラード、ハンティントンF.「Y染色体の物語」 ネイチャー423、第6942号(2003):811-813。</li>
	<li>Ginalski, Krzysztof, Leszek Rychlewski, David Baker, and Nick V. Grishin. "ヒトY染色体の男性特異的領域のタンパク質構造予測。" Proceedings of the National Academy of Sciences 101, no. 8 (2004): 2305-2310.</li>
	<li>Noordam, Michiel J., and Sjoerd Repping. "ヒトY染色体:男性染色体。" Current opinion in Genetics & Development 16, no. 3 (2006): 225-232.</li>
</ol>

y染色体が男性性を決定する

Y染色体は、人間を含むいくつかの脊椎動物および哺乳類に見られる性染色体です。 22対の常染色体に加えて、人間の男性は1本のX染色体と1本のY染色体を持っています。 これらの生物では、Y染色体の有無が雄の形質の発達を決定します。

進化

約3億年前、2つの性染色体は2つの同一の常染色体から分岐しました。 時間が経つにつれて、Y染色体はほとんどの遺伝子を失い、サイズが縮小します。 現在、Y染色体のごく一部だけが X 染色体と配列類似性を共有しています。 サル、マウス、ラット、雄牛、オポッサム、チンパンジー、人間を含む8頭の哺乳類のY染色体に関する大規模な科学的研究では、Y染色体上に非常に類似した18の領域が示された。進化の過程で Y 染色体の大部分が失われたにもかかわらず、これらの領域がすべての哺乳類で保持されているという事実は、Y染色体上の遺伝子がこれらの哺乳類の生存に不可欠であることを示しています。

構造

哺乳類のY染色体には3つの主要な領域があります。Y染色体上の偽常染色体領域はX染色体と相同性を共有しており、減数分裂組換えが起こる可能性があります。したがって、偽常染色体領域に存在する遺伝子は、性関連ではなく常染色体で受け継がれます。2番目の領域は、男性特異的Y染色体領域またはMSYとして指定されるユークロマチン領域です。その長さは23Mbで、男性性のマスター調節因子であるSRY遺伝子や精子形成に必要なZFY遺伝子など、タンパク質をコードする遺伝子はほとんどありません。3番目の領域は、いくつかの反復配列を含むヘテロクロマチン領域です。

突然変異とその影響

Y染色体のMSY領域の欠失は精子の発育に影響を与え、男性不妊の原因となります。たとえば、Y染色体の長腕にあるAZF遺伝子の欠失は、男性の射精液中に精子が見つからない無精子症と呼ばれる状態を引き起こします。 さらに、MSYの特定領域の欠失は精巣胚細胞腫瘍(TGCT)と関連しています。

Y染色体が男性性を決定する

Y染色体は、人間を含むいくつかの脊椎動物や哺乳類に見られる性染色体です。22対の常染色体に加えて、人間は...

Education

JoVE Core

Molecular Biology

分子生物学

Unit 2

ユニット2

Mendelian Genetics

メンデルの遺伝学

KEY TERMS AND CONCEPTS

主要用語と概念

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

punnett squares

Predicting Traits with Punnett Squares

Punnett squares help students predict how traits may be passed from parents to offspring. They are a simple grid used in genetics to organize possible allele combinations. An allele is a version of a gene. The square compares the alleles each parent can give. By filling in the boxes, students can see possible genotypes, which are the genetic makeup of offspring. The results can also help connect those genotypes to traits that may appear in the next generation.

monohybrid crosses

Tracking One Trait in Monohybrid Crosses

Monohybrid crosses track how one trait is passed from parents to offspring. They are used to study inheritance when only a single characteristic is followed at a time. A monohybrid cross can compare the possible outcomes for a monogenic trait, which is a trait controlled by one gene. This approach helps show how one gene can shape different inherited forms of the same characteristic. The method also connects with Mendel's work on genetics. It is a useful way to predict patterns of inheritance...

dihybrid crosses

Predicting Two-Trait Genetic Crosses

Dihybrid crosses are used to predict how two traits can be passed from parents to offspring. A dihybrid cross tracks two genes at the same time, so it helps students see how different alleles can combine in a genetic pattern. This topic is closely tied to Mendelian genetics and independent assortment. Independent assortment means that allele pairs for different traits can separate into gametes independently of one another. When students work through a dihybrid cross, they can compare the...

trihybrid crosses

Forked Line Method for Trihybrid Crosses

Forked line method for trihybrid crosses helps predict the outcome of three-trait Mendelian crosses. A trihybrid cross studies three pairs of contrasting characteristics. It combines three separate monohybrid crosses. Common examples include plant height, seed shape, and seed color. In a typical trihybrid cross, the F1 plants are heterozygous for all three traits. They can produce eight different gametes. After self-fertilization, these gametes can lead to 64 genotype combinations in the F2...

law of independent assortment

Independent Chromosome Assortment in Meiosis

Independent chromosome assortment in meiosis explains how different gene pairs can be inherited independently. This idea is one of Mendel’s laws of inheritance and is often called the law of independent assortment. The pattern depends on how homologous chromosomes line up during meiosis I. Each chromosome pair orients independently of the others, so the maternal and paternal chromosomes can separate into different gametes in many combinations. This random separation helps create genetic...

chi-square analysis

Chi-Square Test in Genetics

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pedigree analysis

Tracing Traits with Pedigree Charts

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multiple allele traits

Multiple Alleles in Trait Inheritance

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incomplete dominance

Incomplete Dominance in Traits and Disease

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lethal alleles

When Genes Cause Embryonic Death

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polygenic traits

Traits Shaped by Many Genes

Polygenic traits are characteristics shaped by many genes acting together. This pattern is different from a single-gene trait, where one gene has a larger effect on the outcome. In polygenic inheritance, each gene adds a small contribution to the final trait. Height is a common example of a polygenic trait. Many genes influence human height, so the result can vary across a wide range. These small genetic effects combine to produce differences that are easy to see in a population. Polygenic...

background and environment affect phenotype

background-and-environment-affect-phenotype

How Genes and Environment Shape Traits

Genes and the environment work together to shape phenotype, or the visible traits of an organism. A phenotype can change because of genetic background, environmental conditions, or both. Factors such as temperature, oxygen availability, and mutagens can all influence how a trait appears. Horses show how one gene can affect coat color and how a modifier gene can change that result. The Extension gene controls pigment production in the coat. The wild-type genotype EE produces black pigment,...

x and y chromosomes

Sex Chromosomes in Human Inheritance

Sex chromosomes help determine biological sex in mammals, including humans. Humans have two sex chromosomes, X and Y. Each diploid cell has 22 pairs of autosomes and one pair of sex chromosomes. A female usually has two X chromosomes, while a male usually has one X chromosome and one Y chromosome. Egg and sperm cells carry only half the usual number of chromosomes. They contain 22 autosomes and one sex chromosome. Every egg has an X chromosome. Sperm cells can carry either an X or a Y...

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

Drosophila Sex Determination by X:A Balance

In Drosophila, sex is determined by the balance between X chromosomes and autosomes, not by the X and Y chromosomes alone. The Y chromosome is active in these flies, but it does not set sex. Instead, it carries genes needed for sperm production in adult males. A normal male Drosophila has one X chromosome and two sets of autosomes. A normal female has two X chromosomes and two sets of autosomes. When this X:A ratio changes, flies can develop different sexual phenotypes, including metamales,...

x-linked traits

X-Linked Inheritance in Families

X-linked inheritance in families explains how traits linked to the X chromosome pass from parents to children. These traits are often tracked through family trees because the pattern can differ between males and females. A male has one X chromosome and one Y chromosome. A female has two X chromosomes. Because of this difference, a trait on the X chromosome can show up in a different way depending on the sex of the child. Family examples often include traits such as color blindness. Studying...

sex linked disorders

Sex-Linked Disorders and Inheritance Patterns

Sex-linked disorders are genetic conditions that follow inheritance patterns tied to the sex chromosomes. These disorders help explain how certain traits can appear more often in one sex than the other. The transcript focuses on examples of sex-linked disorders, including Y-linked infertility, Fragile X syndrome, and Duchenne muscular dystrophy. Y-linked infertility is passed through the Y chromosome, while Fragile X syndrome and Duchenne muscular dystrophy are associated with sex-linked...

dosage compensation

X-Chromosome Balance in Animals

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x-inactivation

X-Inactivation and Barr Bodies

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blood types

Blood Types and Transfusion Matching

Human blood types help determine safe blood transfusion matching. Blood is classified by antigens on the surface of red blood cells and antibodies in the plasma. Correct blood typing matters because an unsafe match can affect transfusion success. The International Society of Blood Transfusion has identified 38 human blood types, and ABO, Rh, and MNS are among the most common. The ABO blood group depends on antigens made by genes on chromosome 9. Red blood cells carry a base glycoprotein called...

blood transfusion and agglutination

Matching Blood Types for Safe Transfusion

Blood transfusion is a medical treatment used to restore blood volume after major blood loss from an accident or a medical procedure. It works by taking blood from a suitable donor and giving it to a recipient. Safe transfusion depends on matching blood types and checking for immune compatibility. The history of blood transfusion began in the 17th century, when early experiments were done in animals. In 1818, James Blundell, a British doctor, performed the first successful human blood...

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 分子生物学は、明確で簡潔なアニメーション ビデオ レッスンを通じて細胞の分子プロセスを紹介します。さらに、科学者の実際のビデオでは、これらの概念の応用が現代の研究室での実際の実験を通じて実証されています。

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

9-12

Biology

Heredity

Genetic mechanisms and inheritance

Tennessee Academic Standards

links-among-engineering-technology-science-and-society

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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Heterochromatin

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Punnett Squares

Monohybrid Crosses

Dihybrid Crosses

Trihybrid Crosses

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Law of Independent Assortment

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Pedigree Analysis

Multiple Allele Traits

Incomplete Dominance

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Lethal Alleles

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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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X-linked Traits

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Meiosis I

Meiosis II

Make and defend a claim based on evidence that inheritable genetic variations may result from: (1) new genetic combinations through meiosis, (2) viable errors occurring during replication, and/or (3) mutations caused by environmental factors. Emphasis is on using data to support arguments for the way variation occurs. Claims should not include the phases of meiosis or the biochemical mechanisms of specific steps in the process.

Y Chromosome Structure and Male Traits

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