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

There are two sex chromosomes in humans: X and Y.
The Y chromosome determines the male sex and is the smallest chromosome of the human genome.
There are three regions in the Y chromosome: the pseudoautosomal portion, which is further divided into two regions - PAR1 and PAR2, the heterochromatic region, and the euchromatic region.
The S-R-Y gene is located in the euchromatic region of the Y chromosome. It plays a vital role in the development of male fetuses.
When an egg carrying an X chromosome fuses with a sperm carrying a Y chromosome, it forms a zygote.
The zygote then continuously divides to form an embryo. At this stage, male and female embryos are developing along the same pathway and are physiologically identical.
During the early stages of development, the embryo has two precursor organs: the Wolffian duct and the Mullerian duct.
The Wolffian duct can differentiate into male genital structures and the Mullerian duct can differentiate into female genital structures.
In the weeks after fertilization, the S-R-Y gene present on the Y chromosome is transcribed and then translated into the S-R-Y protein. The S-R-Y protein initiates the development of testes in the fetus.
&#160;The S-R-Y protein acts as a transcriptional factor and binds to specific sites on the DNA, thus activating the testes forming pathway.
Then, the gonads start secreting several hormones, including anti-mullerian hormone and testosterone.
Anti-mullerian hormone inhibits the development of the Mullerian duct.
Testosterone, on the other hand, initiates the development of the Wolffian duct into vas deferens, ejaculatory ducts, and seminal vesicles.
If this pathway is disrupted and the gonads fail to secrete testosterone and anti-mullerian hormone, the Mullerian duct develops into female reproductive organs even if the fetus is genotypically XY.

the y chromosome determines maleness

The Y chromosome is a sex chromosome&#160;found in several vertebrates and mammals, including humans. In addition to 22 pairs of autosomes, the human males have one X chromosome and one Y chromosome. In these organisms, the presence or absence of the Y chromosome determines the development of male traits.
<h4>Evolution</h4>
Around 300 million years ago, the two sex chromosomes diverged from two identical autosomal chromosomes. Over time, the Y chromosome has lost most of its genes, shrinking in size. Today, only a small part of the Y chromosome shares sequence similarity with the X chromosome. A large scientific study on Y chromosomes in eight mammals, including monkeys, mice, rats, bulls, opossums, chimpanzees, and humans, showed 18 highly similar regions on Y chromosomes. The fact that these regions are retained in all these mammals, despite losing a large portion of Y chromosomes during evolution, shows that the genes on Y chromosomes are vital for the survival of these mammals.
<h4>Structure</h4>
The mammalian Y chromosome has three major regions. The pseudoautosomal regions on the Y chromosome share homology with the X chromosome and can undergo meiotic recombination. Thus, genes present in the pseudoautosomal regions are inherited in an autosomal rather than a sex-linked fashion. The second region is a euchromatin region designated as a Male-specific Y chromosome region or MSY. It spans 23 Mb in length and has few protein-coding genes, such as the SRY gene, a master regulator of maleness and the ZFY gene required for spermatogenesis. The third region is a heterochromatin region that contains several repetitive sequences.
<h4>Mutations and their effects</h4>
Deletions in the MSY region of the Y chromosome affect sperm development and cause male sterility. For example, deletions in the AZF gene on the long arm of the Y chromosome lead to a condition called azoospermia, where spermatozoa are not found in male ejaculate. In addition, deletions in specific regions of MSY are associated with testicular germ cell tumors (TGCTs).

The Y chromosome is a sex chromosome&#160;found in several vertebrates and mammals, including humans. In addition to 22 pairs of autosomes, the human ...

Education

JoVE Core

Molecular Biology

Unit 2

Mendelian Genetics

KEY TERMS AND CONCEPTS

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

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trihybrid crosses

Forked Line Method for Trihybrid Crosses

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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

Multiple alleles can shape how a trait is inherited in a population. A gene may have more than two allele forms, even though each person still carries only two alleles for that gene. These allele combinations can produce traits with more than two possible outcomes. The ABO blood group system is a common example of a multiple allele trait. It shows how different alleles can interact to determine an organism’s phenotype, or observable trait. Multiple allele traits help explain why inheritance...

incomplete dominance

Incomplete Dominance in Traits and Disease

Incomplete dominance is a pattern of inheritance where two alleles both affect a trait in a heterozygous organism. In this case, one allele is not fully dominant over the other. The result is a phenotype that looks like a blend or intermediate form. Gregor Mendel’s pea plant experiments helped explain the usual dominant and recessive pattern. He showed that each gene in a diploid cell has two alleles, one inherited from each parent. In his model, a dominant allele shows its effect with one or...

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 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

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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

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New York State Science Learning Standards

Inheritance and Variation of Traits

HS-LS3-1.

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Dihybrid Crosses

Trihybrid Crosses

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Law of Independent Assortment

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Pedigree Analysis

Multiple Allele Traits

Incomplete Dominance

Gregor Mendel&#39;s work (1822 - 1884) was primarily focused on pea plants. Through his initial experiments, he determined that every gene in a diploid ...

Lethal Alleles

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Polygenic Traits

Background and Environment Affect Phenotype

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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.

X and Y Chromosomes

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X-linked Traits

Sex Linked Disorders

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X-inactivation

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Meiosis I

Meiosis II

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Nondisjunction

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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.

Mutations

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HS-LS3-3

Y Chromosome Structure and Male Traits

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