Sex Linked Traits

Sex-linked traits

A trait associated with a gene that is carried only by the male or female parent.

X-linked

A gene carried on the X chromosome. If a male inherits an X-linked recessive trait from his mother, he expresses that trait because the Y from his father has no counteracting gene. Females are more likely to be carriers of X-linked traits but are less likely to express them.

Hemophilia

An X-linked recessive disorder in which blood fails to clot properly, leading to excessive bleeding if injured.

Color blindness

An x-linked recessive trait that affects a person's ability to perceive some colors. In rare cases, the affected person cannot see any color but this does not affect their ability to see the differences in shade.

Muscular dystrophy

sex linked diseases; group of inherited muscle disorders that cause muscle weakness without affecting the nervous system

Carrier

A person who has one recessive allele for a trait, but does not have the trait; females can be carriers for sex linked diseases but males can not

X chromosome vs Y chromosome

Y is smaller than X so it has fewer genes so often there are genes are the X chromosome that don't exist on the Y chromosome ----> males more susceptible to sex-linked diseases because they have no second allele to mask the recessive one

X-linked recessive inheritance

-males show disorder more than females

-son cannot inherit disorder from his father

X-linked dominant inheritance

All females of the affected father are diseased.

Affected mother can pass on the disease to both male and female offspring.

X chromosome

The sex chromosome found in both men and women. Females have two X chromosomes; males have one. An X chromosome from each parent produces a female child.

Y chromosome

the sex chromosome found only in males. When paired with an X chromosome from the mother, it produces a male child.

sex-linked crosses

(punnett squares)

Must include sex chromosomes to indicate sex as well as genotype

Sex-linked gene

gene located on a sex chromosome, generally the X chromosome

Pedigrees:

Sex-linked dominant vs recessive

Sex-linked dominant:

-Both males and females are affected; often more

females than males are affected

-Does not skip generations

-Affected fathers will pass the trait on to all their

daughters

Sex-linked recessive:

-More males than females are affected

-It is never passed from father to son

-All daughters of affected fathers are carriers