Download Sex-Limited, Linked, and Influenced Traits Some traits are carried on

Sex-Limited, Linked, and Influenced Traits
Some traits are carried on the sex chromosomes, X and Y. Most traits carried are present on only
the X-chromosome. The Y-chromosome is smaller, and so, very few genes are located on this
chromosome.
Sex traits can be categorized into three types of inheritance: sex-limited, sex-linked, and sexinfluenced.
Sex-limited traits are traits that are visible only within one sex. For instance, barred coloring in
chickens normally is visible only in the roosters.
Sex-linked traits would be considered traits like sickle cell anemia and color blindness. They are
said to be linked because more males (XY) develop these traits than females (XX). This is
because the females have a second X gene to counteract the recessive trait. Thus, the trait is more
likely to be visible in the male.
Sex-influenced traits are autosomal traits that are influenced by sex. If a male has one recessive
allele, he will show that trait, but it will take two recessive for the female to show that same trait.
One such gene is baldness.
One of the identified genes involved in male pattern baldness is located on the X chromosome,
which is inherited only from the maternal side in the case of men, but this one gene does not
explain all the cases of male pattern baldness. Baldness in a child cannot be predicted only from
the mother's lineage. There are probably other unidentified autosomal genes that are also
involved. In other words, genetics does play a role in male pattern baldness, but the genes can
come from either parent, not just the mother
The typical pattern of female pattern baldness is different from that of male pattern baldness. The
hair thins all over the head, but the frontal hairline is maintained. There may be a moderate loss of
hair on the crown, but this rarely progresses to total or near baldness as it may in men.
In woman, (using B and b as the alleles) B is actually the recessive trait and b (the gene for nonbaldness) is the dominant trait. In men, it's reversed: B is the dominant trait and b is the recessive
trait. So it's rarer for women to be bald, but it does happen.
Also when women do have the balding gene it happens a lot later in life, when estrogen levels are
lower, so the process starts after menopause, so it still takes time for them to get severely bald
after that.the high estrogen level keeps the baldness from happening(?)