Sex-linked traits
A sex linked trait is a trait that is genetically determined by an allele located on the sex chromosome.
There are different genotypes a person can have for a sex-linked trait. Females can either be homozygous for the trait, heterozygous or don't have the allele for the trait at all.So they are either uneffected, affected or a carrier for the trait. but males, since they have two different sex chromosomes, can only have the allele for the trait o one of their sex chromosomes or don't have it at all. That means a male is either affected or not affected, he can't be a carrier.
Example:
This a sex-linked recessive disorder on the x chromosome. In this disorder, the muscle tissue is continuely damamged so thet the musle becomes weaker and weaker until the individual finally is unable to move and most commonly dies from respiratory damage. The prognosis for people with MD varies according to the type and progression of the disorder. Some cases may be mild and progress very slowly over a normal lifespan, while others produce severe muscle weakness, functional disability, and loss of the ability to walk. Some children with MD die in infancy while others live into adulthood with only moderate disability Some symptoms include frequent falls, difficulty getting up from a lying or sitting position, trouble running and jumping, waddling gait, large calf muscles and learning disabilities.
x-Inactivation
X-inactivation is a process that occurs only in females. One X chromosome is randomly turned off, which alters the phenotype, but not the genotype. Some of the descending cells have the maternal, some te paternal x working. The inactivated x coils up and remains in the nucleus. It's called the barr body. By inactivating one x chromosome in each cell, the number of chromosomes in males and females is equaled out, because after that each cell in their bodies has only one working x chromosome.
