Name: x- and y-linked disorder patterns
Uploaded: 2025-10-23T11:47:17.000Z
Duration: 1 min 43 s
Channel: JoVE

K12 Standards

Virginia  Standards of Learning

HIgh School

Life Science

LS.10

LS.10.c

Sex-linked Disorders

- Certaines maladies héréditairessont causées par des mutations sur un seul gène. 
Lorsqu'elles sont situées sur un chromosome sexuel,on parle de maladie liée au sexe. 
Selon le chromosome sexuel sur lequel se situe le gène,et selon qu'il en faille un ou deux exemplairespour qu'il fonctionne correctement,ces maladies sont considérées comme étant liées à l'Y,dominantes liées à l'X, ou récessives liées à l'X. 
D'abord, les maladies liées à l'Y,comme la stérilité du chromosome Y,sont causées par des mutations des gènes situés sur l'Yet ne peuvent être transmises que de père en fils. 
Ensuite, les maladies dominantes liées à l'X,syndrome de l'X fragile compris,ne nécessitent qu'un exemplaire du gène mutant,affectent tant les hommes que les femmeset ne peuvent être transmises des pères aux fils. 
Pour finir, les maladies récessives liées à l'Xaffectent plus souvent les hommes,car les femmes ont besoin de 2 exemplaires du gène mutant. 
Cependant, les femmes hétérozygotes non affectéespeuvent être porteuses du gène,et ont 50% de risque de les transmettre à leurs fils. 
Par exemple, une maladie récessive liée à l'X,appelée la myopathie de Duchenne, ou DMD,affecte presque exclusivement les hommes. 
La DMD est causée par des mutationsdu gène codant la dystrophine,une protéine impliquée dans la contraction adéquateet la réparation des cellules des muscles squelettiqueset du muscle cardiaque. 
Ces mutations peuvent mener à des changements,structurels ou fonctionnels, dans la protéine dystrophine,sans laquelle les cellules musculaires s'affaiblissentet finissent par s'atrophier.

Colaco, Stacy et Deepak Modi. « Génétique du chromosome Y humain et son association avec l’infertilité masculine. » Biologie de la reproduction et endocrinologie 16, n° 1 (2018) : 14. [<a href="https://dx.doi.org/10.1186%2Fs12958-018-0330-5">Source</a>]

Nakamura, Akinori. « Stratégies thérapeutiques basées sur les mutations pour la dystrophie musculaire de Duchenne : du diagnostic génétique à la thérapie. » Journal de médecine personnalisée 9, n° 1 (2019) : 16. [<a href="https://dx.doi.org/10.3390%2Fjpm9010016">Source</a>]

troubles liés au sexe

Comme les autosomes, les chromosomes sexuels contiennent une variété de gènes nécessaires à la fonction normale du corps. Lorsqu’une mutation dans l’un de ces gènes entraîne des déficits biologiques, le trouble est considéré comme lié au sexe.
 
 Les mutations du chromosome Y sont appelées “ liées à Y ” et n’affectent que les mâles puisqu’ils sont les seuls à porter une copie de ce chromosome. Les mutations du chromosome Y, relativement petit, peuvent avoir un impact sur la fonction sexuelle masculine et les caractéristiques sexuelles secondaires. L’infertilité du chromosome Y est un trouble qui affecte la production de sperme, causée par des suppressions dans les régions du facteur azoospermie (AZF) du chromosome Y. En général, les troubles liés à Y ne sont transmis que de père en fils ; cependant, parce que les mâles affectés ne sont généralement pas pères d’enfants sans technologies de reproduction assistée, l’infertilité du chromosome Y n’est généralement pas transmise à la progéniture.
 
 Les troubles liés à X peuvent être dominants ou récessifs. Les troubles dominants liés à X sont le résultat d’une mutation du chromosome X qui peut affecter les mâles ou les femelles. Cependant, certains troubles, y compris le syndrome du X fragile, affectent les hommes plus sévèrement que les femmes, probablement parce que les mâles n’ont pas de seconde copie normale du chromosome X. Le syndrome du X fragile se caractérise par un large éventail de problèmes de développement, y compris des troubles de l’apprentissage. L’hypophosphatémie liée à X est une autre affection dominante liée à X qui se manifeste par une forme de rachitisme résistante à la vitamine D.
 
 Pour qu’une mutation récessive provoque des déficits biologiques, les deux copies d’un chromosome doivent être mutées. En conséquence, les femelles doivent recevoir deux chromosomes X mutés pour afficher un trouble lié à X. En revanche, les mâles sont affectés si leur unique chromosome X porte la mutation. En conséquence, les mâles sont affectés plus souvent par des maladies récessives liées à X, y compris la daltonisme, la dystrophie musculaire de Duchenne et l’hémophilie.

Troubles liés au sexe

Comme les autosomes, les chromosomes sexuels contiennent une variété de gènes nécessaires au fonctionnement normal du corps. Lorsqu’une mutation dans l’un de ces gènes entraîne ...

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KEY TERMS AND CONCEPTS

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x- and y-linked disorder patterns

X- and Y-linked disorders come from mutations in genes on the sex chromosomes. These genes, like those on autosomes, are needed for normal body function. When a mutation causes a biological problem, the condition is called sex-linked.

Y-linked disorders come from changes in the Y chromosome. They affect only males, because only males carry a Y chromosome. Mutations in this small chromosome can affect male sexual function and secondary sex characteristics. One example is Y-chromosome infertility, which lowers sperm production because of deletions in the azoospermia factor, or AZF, regions of the Y chromosome.

Y-linked disorders are usually passed from father to son. In many cases, affected males do not father children without assisted reproductive technologies. Because of that, Y-chromosome infertility is not typically passed on to offspring.

X-linked disorders can be dominant or recessive. X-linked dominant disorders come from a mutation on the X chromosome and can affect males or females. Fragile X syndrome is one example. It can cause a wide range of developmental problems, including learning disabilities, and it often affects males more severely because they do not have a second normal X chromosome. X-linked hypophosphatemia is another dominant condition, and it causes a vitamin-D-resistant form of rickets.

X-linked recessive disorders require both copies of a chromosome to carry the mutation for females to show the condition. Males are affected if their single X chromosome has the mutation. That is why males are affected more often by X-linked recessive conditions such as color blindness, Duchenne muscular dystrophy, and hemophilia.

X- and Y-Linked Disorder Patterns

genetic lingo

Genotype, Phenotype, and Inheritance

Genotype, phenotype, and inheritance help explain how traits and disease risk are passed from parents to offspring. In diploid organisms, including humans, most other animals, and many plants, somatic cells carry a duplicate set of chromosomes. These chromosome pairs are homologous, with similar length, centromere position, and gene locations. Diploid organisms inherit two versions of each gene, one from each parent. These versions are called alleles, and they sit at the same relative locus,...

punnett squares

Punnett Squares for Predicting Traits

Punnett squares help predict which traits offspring may inherit from two parents. They show possible genotypes, which are pairs of alleles, and can also show the chance of a phenotype, or visible trait, when the inheritance pattern is known. These grids work best for traits controlled by a single gene locus and passed on independently during meiosis. Punnett squares were developed in the early 1900s by Reginald Punnett. His work came after Gregor Mendel’s pea plant experiments revealed the...

monohybrid crosses

Mendel’s Pea Plant Inheritance Ratios

Gregor Mendel used pea plants to study how traits are passed from parents to offspring. His breeding experiments in the 1850s and 1860s showed that inheritance follows clear patterns. He crossed true-breeding plants that differed in one trait and found that dominant traits can hide recessive traits. Mendel focused on seven pea plant traits, and each trait had two forms controlled by a single gene locus. He noticed that true-breeding plants always produced offspring with the same phenotype, or...

dihybrid crosses

Mendel's Law of Independent Assortment

Mendel’s law of independent assortment explains how two traits can be inherited separately. Gregor Mendel tested this idea with pea plants that differed in two characteristics, such as pea color and pea shape. He used true-breeding parents that were homozygous for both traits but showed different phenotypes. In one example, Mendel crossed round, yellow peas with wrinkled, green peas. The parental generation had RRYY and rryy genotypes. Their first-generation offspring were all dihybrids,...

law of segregation

Mendel’s Pea Cross Ratios

Mendel’s pea plant crosses show how traits can disappear in one generation and return in the next. When he crossed plants, one parental trait sometimes seemed to vanish in the F1 generation and reappear in the F2 generation. Mendel used this pattern to explain why some traits are dominant and others are recessive. He proposed that traits are controlled by alleles, which are different versions of a gene. An organism inherits two copies of each gene, one from each parent. In his model, a...

law of independent assortment

Mendel’s Dihybrid Cross and Trait Ratios

Mendel’s dihybrid cross shows how two traits are inherited at the same time. A dihybrid cross is a cross in which both parents are homozygous for two distinct traits, and the F1 generation is heterozygous for both traits. Mendel used pea plants with round yellow peas and wrinkled green peas as an example. One parent had genotype YYRR, and the other had genotype yyrr. In the F1 generation, every plant showed the dominant traits, so the plants were YyRr and had yellow, round peas. The F2...

probability laws

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test cross

Using Test Crosses to Identify Genotypes

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polygenic traits

Polygenic Traits in Human Height

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pedigree analysis

Reading Family Traits in Pedigrees

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multiple allele traits

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epistasis

Gene Masking in Rabbit Fur Color

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nature and nurture

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pleiotropy

SOX10 and Multiple Traits in Pleiotropy

Pleiotropy is when one gene affects more than one trait. The SOX10 gene is a clear example because it can influence pigmentation, hearing, and intestinal movement. These traits may seem unrelated, but they can all be linked to the same gene change. In humans, a deleted region in SOX10 can cause Waardenburg Syndrome Type 4, or WS4. WS4 is an autosomal recessive disorder, which means a person usually inherits two altered copies of the gene. Common signs include a white forelock,...

sex-linked disorders

X- and Y-linked disorders come from mutations in genes on the sex chromosomes. These genes, like those on autosomes, are needed for normal body function. When a mutation causes a biological problem, the condition is called sex-linked. Y-linked disorders come from changes in the Y chromosome. They affect only males, because only males carry a Y chromosome. Mutations in this small chromosome can affect male sexual function and secondary sex characteristics. One example is Y-chromosome...

x-linked traits

X-Linked Inheritance in Families

X-linked inheritance explains how traits on the X chromosome are passed through families. In most mammalian species, females have two X sex chromosomes, while males have one X and one Y. A mutation on one X chromosome may be masked in females by a normal allele on the other X. In males, that same mutation is more likely to show because there is no second normal X to balance it. Traits caused by changes on the X chromosome are called X-linked traits. Color blindness is a well-studied example.

x-inactivation

Barr Bodies and X-Chromosome Balance

Barr bodies and X-chromosome balance help explain how female mammalian cells control gene activity from the X chromosome. The human X chromosome carries far more genes than the Y chromosome. Because males usually have one X chromosome and females have two, females would make twice as many of some proteins without a control system. To prevent that imbalance, female mammalian cells inactivate nearly all the genes on one X chromosome during early embryonic development. The inactive X condenses...

non-nuclear inheritance

Maternal DNA in Mitochondria and Chloroplasts

Maternal DNA in mitochondria and chloroplasts explains how some genes are inherited outside the nucleus. Most DNA is in the nucleus, but mitochondria and chloroplasts in the cell cytoplasm also carry their own DNA and can copy it independently of nuclear DNA. Mitochondria are found in both plant and animal cells. They are called the powerhouses of eukaryotic cells because they break down glucose to make energy for cellular activity. Mitochondrial DNA has about 37 genes, and many help with...

chromosomal theory of inheritance

How Genes Map to Chromosomes

Genes map to chromosomes, and this idea explains how Mendel’s inheritance patterns work. Gregor Mendel published his pea plant breeding results in 1866. He showed that physical traits follow predictable patterns. At the time, scientists did not yet know that genes existed. Mendel used the word "factors" for the hereditary units he studied. The details behind Mendel’s laws of segregation and independent assortment were still unknown for many years. In the late 1800s, better microscopes and...

key terms and concepts

Learn how X-linked and Y-linked mutations affect inheritance, with examples including Fragile X syndrome, Y-chromosome infertility, color blindness, and hemophilia.

X- and Y-Linked Disorder Patterns | JoVE K12

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heredity-inheritance-and-variation-of-traits

Heredity: Inheritance and Variation of Traits

HS-LS3-1

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New York State Science Learning Standards

Inheritance and Variation of Traits

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X- and Y-Linked Disorder Patterns

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