pedigrees & more genetics. pedigree male female heterozygous shows trait
TRANSCRIPT
Probabilities
Aa aaChild will have recessive trait?
aa
Chance of “a” allele from dad?
1/2
Chance of “a” allele from mom?
2/2 (1)
Total
1/2 x 1 = 1/2
X-linked Recessives: More commonly seen in Males
• Why?• Males only need one recessive
allele to see trait.• E.g. Color-blindness
• XcY = colorblind male• XcXc = colorblind female• XcX = carrier female
A woman with normal vision whose father was colorblind marries a colorblind male. What percent of the couple’s sons will be colorblind?
1. All
2. 75%
3. 50%
4. 25%
A woman with normal vision whose father was colorblind marries a colorblind male. What percent of the couple’s sons will be colorblind?
1. All
2. 75%
3. 50%
4. 25%
Xc X
Xc XcXc XcX
Y XcY XY
Epistasis
• A gene at one locus alters the expression of a gene at another locus.
• Example: – Black coat (B) is
dominant to brown (b)– Pigment color (C) is
dominant to no pigment color (c)
Polygenic Traits
• Additive effect of multiple genes on a single phenotype
• Results in normal distribution
• Examples: skin color, height