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

- [Relatore] Alcune malattie ereditarie

sono causate da mutazioni
di un singolo gene.

E quando si trovano su
un cromosoma sessuale,

la malattia si definisce "sex-linked".

In base al cromosoma sessuale
sul quale il gene si colloca

e a seconda del fatto che una
o due copie siano necessarie

per il corretto funzionamento,

tali malattie si definiscono Y-linked,

X-linked dominanti o X-linked recessive.

Le prime, le malattie Y-linked
come l'infertilità del

cromosoma Y sono causate da
mutazioni dei geni posti sul

cromosoma Y e si trasmettono
solo da padre a figlio.

Le seconde, le malattie X-linked dominanti

come la sindrome dell'X fragile

richiedono una sola copia del gene mutato,

possono colpire sia i
maschi che le femmine

e non si trasmettono da padre a figlio.

Infine, le malattie X-linked recessive

colpiscono più i maschi, perché

nelle femmine sono necessarie
2 copie del gene mutato.

Però le femmine eterozigoti
sane possono essere portatrici e

hanno il 50% di probabilità di
passare la malattia ai figli.

Ad esempio, una malattia
X-linked recessiva

chiamata Distrofia
Muscolare di Duchenne, DMD

colpisce quasi esclusivamente i maschi.

La DMD è causata da mutazioni
del gene che codifica per la

distrofina, la proteina
che contribuisce alla

corretta contrazione e
riparazione delle cellule

muscolari scheletriche e cardiache.

Tali mutazioni possono
portare a cambiamenti

strutturali e funzionali
della proteina distrofina

senza la quale le cellule
muscolari si indeboliscono

fino ad atrofizzarsi.

Colaco, Stacy e Deepak Modi. "Genetica del cromosoma Y umano e la sua associazione con l'infertilità maschile". Biologia riproduttiva ed endocrinologia 16, n. 1 (2018): 14. [<a href="https://dx.doi.org/10.1186%2Fs12958-018-0330-5">Sorgente</a>]

Nakamura, Akinori. "Strategie terapeutiche basate su mutazioni per la distrofia muscolare di Duchenne: dalla diagnosi genetica alla terapia." Giornale di medicina personalizzata 9, n. 1 (2019): 16. [<a href="https://dx.doi.org/10.3390%2Fjpm9010016">Sorgente</a>]

malattie legate al sesso

Come gli autosomi, i cromosomi sessuali contengono una varietà di geni necessari per la normale funzione corporea. Quando una mutazione in uno di questi geni si traduce in deficit biologici, il disturbo è considerato legato al sesso.

Le mutazioni del cromosoma Y sono chiamate "Y-linked" e colpiscono solo i maschi poiché da soli portano una copia di quel cromosoma. Le mutazioni al cromosoma Y relativamente piccolo possono avere un impatto sulla funzione sessuale maschile e sulle caratteristiche secondarie del sesso. L'infertilità del cromosoma Y è un disturbo che colpisce la produzione di spermatozoi, causato da delezioni alle regioni del fattore di azospermia (AAF) del cromosoma Y. In generale, i disturbi legati all'Y vengono trasmessi solo di padre in figlio; tuttavia, poiché i maschi affetti in genere non hanno figli padre senza tecnologie di riproduzione assistita, l'infertilità del cromosoma Y non viene in genere trasmessa alla prole.

I disturbi X-linked possono essere dominanti o recessivi. I disturbi dominanti x-linked sono il risultato di una mutazione del cromosoma X che può colpire sia i maschi che le femmine. Tuttavia, alcuni disturbi, tra cui la sindrome dell'X Fragile, colpiscono i maschi più gravemente rispetto alle femmine, probabilmente perché i maschi non hanno una seconda, normale copia del cromosoma X. La sindrome dell' X fragile è caratterizzata da una vasta gamma di problemi di sviluppo, tra cui i deficit di apprendimento. L'ipofosfatemia X-linked è un'altra condizione dominante legata all'X che si manifesta in una forma resistente alla vitamina D di Rickets.

Affinché una mutazione recessiva causi deficit biologici, entrambe le copie di un cromosoma devono essere mutate. Di conseguenza, le femmine devono ricevere due cromosomi X mutati per visualizzare un disturbo x-linked. Al contrario, i maschi sono colpiti se il loro singolo cromosoma X porta la mutazione. Di conseguenza, i maschi sono colpiti più spesso da condizioni recessive legate all'X, tra cui daltonismo, distrofia muscolare di Duchenne ed emofilia.

Malattie legate al sesso

Come gli autosomi, i cromosomi sessuali contengono una varietà di geni necessari per la normale funzione del corpo. Quando una mutazione in uno di questi geni provoca ...

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KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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,...

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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

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law of independent assortment

Mendel’s Dihybrid Cross and Trait Ratios

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test cross

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Reading Family Traits in Pedigrees

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polygenic traits

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epistasis

Gene Masking in Rabbit Fur Color

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pleiotropy

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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

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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

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New York State Science Learning Standards

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X- and Y-Linked Disorder Patterns

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