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

- [Anlatıcı] Aynı kromozomun birden çok kopyasını taşıyan organizmalarda, örneğin iki X kromozomu olan dişilerde, erken gelişim evrelerinde bunu dengeleyici bir süreç gerekli olur.
 X kromozomunun inaktivasyonu denen süreçte hücredeki kromozomlardan rastgele bir tanesi aynı genin aşırı ekspresyonunu önlemek için etkisiz hale gelir.
 İnaktivasyona uğrayan kromozom yoğunlaşarak Barr cisimciği adındaki kompakt yapıyı oluşturur.
Bu yapı transkripsiyondan etkilenmez.
 Her X kromozomunun ortasına yakın bir yerde bir X inaktivasyon merkezi bulunur ve birbirini tamamlayan iki dizi içerir: Biri, başka düzenleyici dizilerin yanında RNA kodunun açılması içindir ve buna XIST ya da TSIX adı verilir.
 X inaktivasyonunu başlatan aktivatörler inaktivasyona uğrayacak olan kromozomda XIST transkripsiyonunu gerçekleştirir.
Böylece oluşan RNA molekülleri, içinden çıktıkları XIST kromozomunun yüzeyini kaplar.
 Bu adımdan sonra gerçekleşen karmaşık olaylarda proteinlere eşleme yapılır, DNA yeniden şekillenir ve Barr cisimciği oluşur.
 TSIX, aktif kromozomdan anti-anlam doğrultusunda XIST'e transkripte edilir ve tamamlayıcı bağlamayla XIST aktivitesini bastıracak şekilde etki gösterir.
Barr cisimciği halinde inaktive olmuş kromozom organizmanın yaşamı boyunca çok istikrarlıdır ve her mitoz hücre bölünmesinde yeni hücreye aktarılır.
 Örneğin, alaca kürklü dişi kedilerin kürklerinin bu renk ve desende olmasının nedeni, hücrelerinde kürk rengini kodlayan genlerden birinin X ile bağlantılı olup vücutlarının değişik bölgelerinde rastgele inaktivasyona uğramasıdır.

Ahn, J. ve J. X. Lee. "X kromozomu: X inaktivasyonu." Doğa Eğitimi 1, hayır. 1 (2008): 24. [<a href="https://www.nature.com/scitable/topicpage/x-chromosome-x-inactivation-323">Kaynak</a>]

Disteche, Christine M. ve Joel B. Berletch. "X-Kromozom İnaktivasyonu ve Kaçış." Genetik Dergisi 94, no. 4 (Aralık 2015): 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/">Kaynak</a>]

x inaktivasyonu

İnsan X kromozomu, Y kromozomundaki gen sayısının on katından fazlasını içerir. Erkeklerde yalnızca bir X kromozomu olduğu ve dişilerde iki tane olduğu için, dişilerin iki kat daha fazla protein üretmesi beklenebilir ve bu da istenmeyen sonuçlar doğurabilir.

Bunun yerine, bu olası sorundan kaçınmak için dişi memeli hücreleri, erken embriyonik gelişim sırasında X kromozomlarından birindeki neredeyse tüm genleri etkisiz hale getirir. Hücre çekirdeğini çevreleyen nükleer zarfta, inaktive edilmiş X kromozomu, Barr gövdesi adı verilen küçük, yoğun bir top halinde yoğunlaşır. Bu durumda, X'e bağlı genlerin çoğu transkripsiyon için erişilebilir değildir.

Plasental memelilerde, inaktive edilmiş X kromozomu —maternal veya paternal— rastgele belirlenir (ancak keseli hayvanlar tercihen baba X kromozomunu inaktive eder). Bir hücrede X inaktivasyonu, diğer hücrelerdeki X inaktivasyonundan da bağımsızdır. Böylece, embriyonik hücrelerin yaklaşık yarısı maternal X kopyasını inaktive eder; kalan yarısı baba kopyayı etkisiz hale getirerek bir mozaik oluşturur. Bu hücreler çoğaldığında, inaktive edilmiş aynı X kromozomuna sahip hücreler üretirler. Özellikle, Barr gövdeleri yumurtalıkların içindeki yumurtaya dönüşen hücrelerde yeniden etkinleştirilir.

X inaktivasyonu, dişi kaplumbağa kabuğu ve patiska kedilerinin görünümünü açıklar. Bu kediler, X kromozomunda bulunan siyah kürk ve turuncu kürk için alellere sahip bir gen için heterozigottur. Benekli kürkleri, hücre gruplarındaki siyah ve turuncu kürk alellerinin rastgele inaktivasyonundan kaynaklanır (patiska kedilerinin ayrıca farklı bir kromozomun neden olduğu beyaz kürk yamaları vardır). Erkek kaplumbağa kabuğu renkli kediler ve patiska kedileri var olmalarına rağmen, fazladan bir X kromozomuna sahiptirler ve genellikle kısırdırlar.

X inaktivasyonu, ekstra X kromozomlarının neden olduğu koşulların ciddiyetini azaltır. Klinefelter sendromlu erkekler, ekstra X kromozomlarını etkisiz hale getirmek için Barr gövdeleri oluşturur. Üçlü X sendromlu kadınlar, fazla X kromozomu veya kromozomları için ek Barr gövdeleri oluşturur.

X inaktivasyonu

İnsan X kromozomu, Y kromozomundakinin on katından fazla gen içerir. Erkeklerde sadece bir X kromozomu ve dişilerde iki X kromozomu bulunduğundan, ...

Education

JoVE Core

Molecular Biology

Moleküler Biyoloji

Unit 2

Ünite 2

Mendelian Genetics

Mendel Genetiği

KEY TERMS AND CONCEPTS

TEMEL TERİMLER VE KAVRAMLAR

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 Moleküler Biyoloji, hücrenin moleküler süreçlerini açık ve özlü animasyonlu video dersleriyle sergiler. Buna ek olarak, bilim insanı-eylem videolarında, bu kavramların uygulaması modern laboratuvarlarda gerçek deneylerle gösterilmektedir.

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

What are Cells?

Cells are the smallest and basic units of life, whether it is a single cell that forms the entire organism, e.g., in a bacterium, or trillions of them, ...

the-tree-of-life-bacteria-archaea-and-eukaryotes

The Tree of Life - Bacteria, Archaea, and Eukaryotes

Prokaryotic Cells

Prokaryotes are small unicellular organisms that include the domains &#8212; Archaea and Bacteria. Bacteria include many common microorganisms, such as ...

Eukaryotic Compartmentalization

One of the distinguishing features of eukaryotic cells is that they contain membrane-bound organelles, such as the nucleus and mitochondria, that carry ...

Eukaryotic Evolution

The endosymbiont theory is the most widely accepted theory of eukaryotic evolution; however, its progression is still somewhat debated. According to the ...

Animal and Plant Cell Structure

Animal and plant cells not only differ in their structure, function, and mode of nutrition but also in how they reproduce, specialize, and organize into ...

Cytoplasm

The cytoplasm consists of organelles and a framework of protein scaffolds called the cytoskeleton suspended in an aqueous solution, the cytosol. The ...

The Nucleus

The nucleus is a membrane-bound organelle that acts as a control center in a eukaryotic cell. It contains chromosomal DNA, which controls gene expression ...

The DNA Helix

Deoxyribonucleic acid, or DNA, is the genetic material responsible for passing traits from generation to generation in all organisms and most viruses. DNA ...

The Central Dogma

The central dogma explains the flow of genetic information from DNA nucleotides to the amino acid sequence of proteins.
RNA is the Missing Link Between ...

DNA Packaging

DNA as a Genetic Template

Two structural features of the DNA molecule provide a basis for the mechanisms of heredity: the four nucleotide bases and its double-stranded nature. The ...

Organization of Genes

Chromosome Structure

A functional eukaryotic chromosome must contain three elements: a centromere, telomeres, and numerous origins of replication.
The centromere is a DNA ...

Chromosome Replication

Before a cell can divide, it must accurately replicate all of its chromosomes, including the DNA and its associated histone and non-histone ...

The Nucleosome

DNA in a human cell is almost 2m long and it is packed inside a tiny nucleus that is only a few microns in diameter. The level of compaction of DNA inside ...

The Nucleosome Core Particle

Nucleosomes are the DNA-histone complex, where the DNA strand is wound around the histone core. The histone core is an octamer containing two copies of ...

Nucleosome Remodeling

Nucleosomes are the basic units of chromatin compaction. Each nucleosome consists of the DNA bound tightly around a histone core, which makes the DNA ...

Chromatin Packaging

Each human somatic cell contains 6 billion base-pairs of DNA. Each base-pair is 0.34 nm long, which means that each diploid cell contains a staggering 2 ...

Karyotyping

Histone Modification

The histone proteins have a flexible N-terminal tail extending out from the nucleosome. These histone tails are often subjected to post-translational ...

Spreading of Chromatin Modifications

The histone&#160;proteins in the nucleosomes are post-translationally modified (PTM) to increase or decrease access to DNA. The commonly observed PTMs are ...

Histone Variants at the Centromere

Histone variants are the histone proteins with structural and sequence variations. These variants may be regarded as &#8220;mutant&#8221; forms that ...

Inheritance of Chromatin Structures

Epigenetics is the study of inherited changes in a cell&#39;s phenotype without changing the DNA sequences. It provides a form of memory for the ...

Euchromatin

The extent of chromatin compaction can be studied by staining chromatin using specific DNA binding dyes. Under the microscope, the dense-compacted regions ...

Heterochromatin

chromatin-position-affects-gene-expression

Chromatin Position Affects Gene Expression

Chromatin is the massive complex of DNA and proteins packaged inside the nucleus. The complexity of chromatin folding and how it is packaged inside the ...

Punnett Squares

Monohybrid Crosses

Dihybrid Crosses

Trihybrid Crosses

Trihybrid Crosses
Some of Mendel&#8217;s crosses examined three pairs of contrasting characteristics. Such a cross is called a trihybrid cross. A ...

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

Among mammals, the gender of an organism is determined by the sex chromosomes. Humans have two sex chromosomes, X and Y. Every human diploid cell has 22 ...

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 ...

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

In animals, gender is determined by the number and type of sex chromosome. For example, human females have two X chromosomes, and males have one X and one ...

What is Meiosis?

Meiosis is the process by which diploid cells divide to produce haploid daughter cells. In humans, each diploid cell contains 46 chromosomes, half from ...

Meiosis I

Meiosis II

Meiosis vs. Mitosis

Crossing Over

Crossing over is the exchange of genetic information between homologous chromosomes during prophase I of meiosis I. Genetic recombination gives rise to ...

Nondisjunction

Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate correctly and move to the opposite poles of the cells. This ...

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

Mutations are changes in the sequence of DNA. These changes can occur spontaneously or they can be induced by exposure to environmental factors. Mutations ...

Base-pairing and DNA Repair

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

Description

Transcript

Tags

More videos by Standards