Name: x-inactivation and barr bodies
Uploaded: 2021-04-07T12:11:58.000Z
Duration: 1 min 58 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

X-inactivation

- [해설] 똑같은 염색체를 여러 개가진 유기체가령 X 염색체가 두 개인 여성의 경우발달 초기에 유전자량 보전 과정이이루어져야 합니다.X 염색체 불활성화, 줄여서 XCI는세포 안에 있는 염색체 중 하나가무선적으로 침묵되어 동일 유전자의 과표현을방지하는 과정입니다.불활성화된 염색체는 압축되어바소체라는 조밀한 구조물이 됩니다.바소체에 대해서는 전사가 이루어질 수 없죠.모든 X 염색체 중간쯤에는X-불활성화 센터라는 영역이 있습니다.여기에는 비암호화 RNA에 대한 두 개의상보적 염기서열, XIST와 TSIX가다른 조절서열과 함께 들어가 있습니다.XCI는 불활성화할 염색체의XIST 전사를 촉진하는 활성체의 작용으로활동을 시작합니다.그 결과물인 RNA 분자는 자신이 생성된XIST 염색체를 감쌉니다.이 단계에 이어 여러 사건이 복잡하게 일어납니다.단백질 파트너 채택과DNA 모양 수정, 바소체 생산 등이죠.TSIX는 활성화 염색체에서 XIST의 안티센스(역배열) 방향으로전사가 되며상보적 결합을 통해 XIST의 활성화를 억제합니다.불활성화되어 바소체 형태가 된 염색체는유기체의 일생 내내 매우 안정적인 상태이며모든 세포의 유사분열 시 전달됩니다.예를 들면 암컷 삼색고양이의거북이 껍질 같은 털 색깔 패턴은털 색깔에 관여하는 유전자 중 하나가 X 염색체에 연결되어 있으며몸의 여러 영역에서 무선적으로침묵되기 때문에 나타납니다.

Ahn, J., and J. X. Lee. "X 염색체: X 불활성화." Nature Education 1, no. 1 (2008): 24. [<a href="https://www.nature.com/scitable/topicpage/x-chromosome-x-inactivation-323">출처</a>]

Disteche, Christine M. 및 Joel B. Berletch. "X-염색체 비활성화 및 탈출." Journal of Genetics 94, no. 4 (2015년 12월): 591–99. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4826282/"> </a>[<a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4826282/">출처</a>]

x-비활성화

인간 X 염색체는 Y 염색체보다 10배 이상의 유전자 수를 가지고 있습니다. 남성은 오직 하나의 X 염색체를 가지고 있고, 여성은 두 개의 X 염색체를 가지고 있기 때문에, 여성에게서 두 배의 단백질이 생산되리라 기대할 수도 있습니다.
 
 그러나 암컷 포유류 세포는 초기 배아 발달 중 X 염색체 중 하나에 있는 거의 모든 유전자를 비활성화(X-chromosome inactivation)합니다. 세포핵을 둘러싼 핵막안에서 비활성화된 X염색체는 바소체(Barr body)라고 불리는 작고 밀도가 높은 공으로 응축됩니다. 이 상태에선 대부분의 X 연관 유전자가 전사(transcription)될 수 없습니다.
 
 태반 포유류에서 비활성 X 염색체(모계 또는 부계)는 무작위로 결정됩니다(하지만, 유대동물은 우선적으로 부계 X 염색체를 비활성화합니다). 한 세포의 X 비활성화는 다른 세포에서의 X 비활성화와 독립적입니다. 따라서, 약 절반의 배아 세포는 모계 X 사본을 비활성화하고, 나머지 절반은 부계 사본을 비활성화하여 모자이크를 생성합니다. 이 세포들이 복제되면 같은 X 염색체가 비활성화된 세포를 생성합니다. 주목할 점은, 바소체는 난자가 되는 난소 내 세포에서 다시 활성화합니다.
 
 X 비활성화는 암컷 삼색고양이의 출현을 설명합니다. 이 고양이들은 X염색체에 위치한 검은 털과 주황색 털에 대한 대립유전자(allele)가 있는 유전자에 이형접합적(heterozygous)입니다. 얼룩덜룩한 털은 세포 집단 내 검은색과 주황색 털의 무작위 비활성화에서 비롯됩니다(삼색고양이는 다른 염색체에 의해 야기되는 하얀 털을 가지고 있습니다. 수컷 삼색고양이도 존재하지만, 이 고양이들은 여분의 X 염색체를 가지고 있고 일반적으로 불임입니다.
 
 X 비활성화는 여분의 X 염색체에 의해 야기되는 상황의 심각성을 줄여줍니다. 클라인펠터 증후군(Klinefelter syndrome)을 가진 남성은 여분의 X 염색체를 비활성화하기 위해 바소체를 형성합니다. 삼중 X 증후군(Triple X syndrome)을 가진 여성은 여분의 X 염색체를 위해 추가적인 바소체를 형성합니다.

X-비활성화

인간의 X 염색체는 Y 염색체보다 10배 이상의 유전자를 포함하고 있습니다. 남성은 X 염색체가 하나뿐이고 여성은 두 개의 염색체를 가지고 있기 때문에 ...

Education

교육

JoVE Core

Molecular Biology

분자생물학

Unit 2

제2단원

Mendelian Genetics

멘델의 유전학

KEY TERMS AND CONCEPTS

주요 용어 및 개념

x-inactivation and barr bodies

X-inactivation is a process that reduces gene activity on one X chromosome. It helps balance gene expression in cells that have more than one X chromosome. A key result of this process is the formation of a Barr body, which is the inactive X chromosome seen in the nucleus.

This topic also includes Xist, a gene linked to X-inactivation. Xist produces RNA that coats the X chromosome and helps turn it off. Together, Xist and the Barr body show how cells control X-linked genes during development and cell function.

X-Inactivation and Barr Bodies

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

The chi-square test in genetics helps compare expected and observed results. It is a statistical hypothesis test used to see whether a difference between an expected value and an observed value is significant. In genetics, it helps decide whether to accept or reject a hypothesis based on how far the observed data moves from the expected data. The test was developed by Pearson in 1990. The first step is to set up a null hypothesis. This hypothesis says there is no real difference between the...

pedigree analysis

Tracing Traits with Pedigree Charts

Pedigree analysis uses family trees, called pedigrees, to trace how traits and diseases pass from one generation to the next. A pedigree chart helps scientists and students see inheritance patterns clearly across relatives. The chart uses standard symbols to show family members and their relationships. It can reveal whether a trait is likely passed through dominant or recessive inheritance, and it can also help identify patterns linked to sex chromosomes. By studying a pedigree, it is...

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

Lethal alleles can change inheritance patterns by causing death before birth. In mice, Lucien Cuénot studied the agouti gene, which helps control coat color through an agouti-signaling protein that affects melanin distribution in mammals. The wild-type allele produces a gray-brown coat, while the mutant allele produces a yellow coat. Cuénot also found that the yellow allele was linked to yellow mouse obesity syndrome. This syndrome is associated with early-onset obesity and tumors. When he...

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

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.

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

X-chromosome balance in animals helps equalize gene expression between males and females. Sex can be determined by the number and type of sex chromosomes. In humans, females have two X chromosomes and males have one X and one Y chromosome. In C. elegans, one X chromosome is male, while two X chromosomes make a hermaphrodite. The X chromosome carries more than sex-related genes. It also includes genes involved in body functions such as brain development and the immune system. Because males and...

x-inactivation

X-inactivation is a process that reduces gene activity on one X chromosome. It helps balance gene expression in cells that have more than one X chromosome. A key result of this process is the formation of a Barr body, which is the inactive X chromosome seen in the nucleus. This topic also includes Xist, a gene linked to X-inactivation. Xist produces RNA that coats the X chromosome and helps turn it off. Together, Xist and the Barr body show how cells control X-linked genes during development...

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

Learn how X-inactivation reduces gene activity on one X chromosome and leads to Barr body formation, with Xist helping silence the chromosome.

X-Inactivation and Barr Bodies | JoVE K12

molecular biology

JoVE Core 분자생물학은 명확하고 간결한 애니메이션을 통해 분자 단계에서 일어나는 세포 과정을 설명합니다.또한, 과학자가 직접 실험을 진행하는 실사 영상을 통해 분자생물학 개념의 응용 사례를 보여줍니다.

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

9-12

Biology

Heredity

Genetic mechanisms and inheritance

Alabama Course of Study Science

Heredity: Inheritance and Variation of Traits

9-12.B.3.11.a

Texas Essential Knowledge and Skills

BIO.8

BIO.8.B

myJoVE Corporation

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Euchromatin

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Heterochromatin

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Chromatin Position Affects Gene Expression

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Punnett Squares

Monohybrid Crosses

Dihybrid Crosses

Trihybrid Crosses

Trihybrid Crosses
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Law of Independent Assortment

Chi-square Analysis

The chi-square test is a statistical hypothesis test. It is used to check whether there is a significant difference between an expected value and an ...

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

Agouti: A Lethal Allele
Lucien Cu&#233;not discovered lethal alleles in 1905 while studying the inheritance of coat color in mice. The agouti gene is ...

Polygenic Traits

Background and Environment Affect Phenotype

Although the genetic makeup of an organism plays a major role in determining the phenotype, there are also several environmental factors, such as ...

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.

HS-LS3-1

X and Y Chromosomes

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The Y Chromosome Determines Maleness

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The Ratio of X Chromosome to Autosomes

In most organisms, sex is determined by the ratio of X and Y chromosomes. However, in some organisms, such as Drosophila and C.elegans, sex is determined ...

X-linked Traits

Sex Linked Disorders

Dosage Compensation

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Meiosis I

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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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Apply concepts of statistics and probability to explain the variation and distribution of expressed traits in a population. Emphasis is on distribution and variation of traits in a population and the use of mathematics (e.g., calculations of frequencies in Punnett squares, graphical representations) to describe the distribution.

HS-LS3-3

X-Inactivation and Barr Bodies

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