Genetics 3

Question 1

How do we label genes and their alleles for for sex-linked traits?

Answer 1

Recall:
Male = XY
Female = XX

Sex-linked genes:

FEMALES: MALES:

X^A X^A X^A Y (homozygous Dominant)
X^A X^a X^a Y ( homozygous Recessive)
X^a X^a N/A. (Heterozygous)

Question 2

X-linked rescessive: (sex-linked)

Answer 2

• Males often have the disease
• females are carriers (Carries the bad gene but does not express it). Because:
  a) their father has the gene and the mother is not a carrier.
  b) their mother is a carrier and father is unaffected
• every affected son Has a carrier mother and healthy father
• trait often skips a generation

Question 3

X-linked dominant:

Answer 3

• both males and females re equally affected
• if father is affected, all daughters are affected but no sons
• if mother is affected about half her children will be affected (both son and daughter)
• the trait does not skip a generation