2. A black guinea pig crossed with an albino guinea pig produced 12 black offspr
ID: 11079 • Letter: 2
Question
2. A black guinea pig crossed with an albino guinea pig produced 12 black offspring. When the albino was crossed with a second black one, 7 blacks and 5 albinos were obtained. What is the best explanation for this genetic situation? Write genotypes for the parents, gametes, and offspring.3. The litter resulting from the mating of two short-tailed cats contains three kittens without tails, two with long tails, and six with short tails. What would be the simplest way of explaining the inheritance of tail length in these cats? Show the genotypes.
4. A normal vision man and woman produce three boys, one of which is colorblind and the other two with normal vision. What are the genotypes of the parents? (This is a sex-linked problem)
Explanation / Answer
2. A black guinea pig crossed with an albino guinea pig produced 12 black offspring.
When the albino was crossed with a second black one , 7 blacks and 5 albinos were obtained.
What is the best explanation for this genetic situation? Write genotypes for the parents, gametes, and offspring.
B-dominant –balck trait,b-----recessive albino
BB X bb
GAMETES
B
B
b
Bb black
Bb black
b
Bb black
Bb black
Bb-black
albino was crossed with a second black one
parents ---Bb xbb
GAMETES
B
b
b
Bb black
bb albino
b
Bb black
bb albino
3. The litter resulting from the mating of two short-tailed cats contains three kittens without tails, two with long tails, and six with short tails. What would be the simplest way of explaining the inheritance of tail length in these cats? Show the genotypes.
TNTN-NO TAIL
TLTL ----LONG TAIL
TNTL--------- short-tailed
TNTL--------- short-tailed X TNTL--------- short-tailed
PRODUCES ALL ABOVE GENOTPYES
4. A normal vision man and woman produce three boys, one of which is colorblind and the other two with normal vision. What are the genotypes of the parents? (This is a sex-linked problem)
Mother is carrier
PARENTS MALE X Y X Xc X Mother is carrier
Xc
X
X
X Xc carrier
X X NORMAL
Y
Y Xc COLORBLIND
XY NORMAL
GAMETES
B
B
b
Bb black
Bb black
b
Bb black
Bb black
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