Transcript SEX-LINKED GENES

SEX-LINKED
GENES
a. Genes that are
carried on the sex
chromosomes (X & Y)
are called sex-linked
genes
b. the traits they
control are called
sex-linked traits
c. there are both
dominant and
recessive alleles for
sex-linked genes
d. sex-linked traits show
up much more often in
a male because males
do not have a matching
X chromosome to mask
a recessive allele
e. When a recessive allele is present
it will be
expressed
in a male
f. red-green
colorblindness is a
sex-linked trait
g. Hemophilia
(the bleeder’s
disease) is also a
sex-linked trait
h. A person who has
an allele for the trait
but does not show
the trait is said to be
a carrier
i. Sex-linked
traits are passed
from mother to
son and father to
daughter
Write the genotypes for the following:
phenotypes of red-green colorblindness.
Normal male
normal female carrying no colorblind
alleles
colorblind male
normal female carrying the colorblind
allele
colorblind female
Write the phenotypes for the following
genotypes:
XH Xh
XH xH
XH Y0
Xh Y0
A woman who is a carrier for hemophilia
marries a man with hemophilia. Could
any of their children have hemophilia? If
so, would the child be male or female?
A woman who is heterozygous for
hemophilia marries a normal male. What
are the possible phenotypes of their
children?
A colorblind man marries a female who is
a carrier for colorblindness. What is the
probability that they will have a child who
is colorblind?
A colorblind male marries a female who is
not colorblind (homozygous). What are
the possible phenotypes of their children?