4. In cats the m allele is lethal. The homozygous recessive dies while still an

Question

4. In cats the m allele is lethal. The homozygous recessive dies while still an embryo inside the mother cat. In
heterozygotes, the spine does not develop normally, and the cat is born without a tail – this breed of cat is
called a Manx. If two Manxes mate, what is the probability that any of their surviving kittens will be a
Manx?


5. In pea plants, the allele for yellow pods is dominant over the allele for green pods. If you cross heterozygous
pea plant with one that breeds true for green pods, what is the resulting genotypic ratio?


6. Caucasians have one of three main types of hair on their heads: straight, wavy and curly, with wavy being
intermediate between straight and curly. What offspring would be expected between two wavy-haired
parents?

Explanation / Answer

4. In cats the m allele is lethal. The homozygous recessive dies while still an embryo inside the mother cat. In heterozygotes, the spine does not develop normally, and the cat is born without a tail – this breed of cat is called a Manx.

If two Manxes mate, what is the probability that any of their surviving kittens will be a
Manx?

m allele is lethal ,
GENOTYPE mm ------ homozygous recessive dies
GENOTYPE mM -------- heterozygotes ----SURVIVES ---Manx.

Manx GENOTYPE= mM
Manx    mM X Manx    mM

MM-----------25%------------NORMAL

mM-----------50%-------------heterozygotes ----SURVIVES ---Manx. answer

mm-------------25%---------DIES



5. In pea plants, the allele for yellow pods is dominant over the allele for green pods. If you cross heterozygous
pea plant with one that breeds true for green pods, what is the resulting genotypic ratio?

yellow pods is dominant over the allele for green pods

yellow pods--------Y

green pods--------y

Yy    x yy       green pods,

Yy------------yellow pods-

yy----------green pods,

what is the resulting genotypic ratio?

1:1

6. Caucasians have one of three main types of hair on their heads: straight, wavy and curly, with wavy being
intermediate between straight and curly. What offspring would be expected between two wavy-haired
parents?

straight,-------SS

wavy---------Ss-------------intermediate in complete dominance

curly,--------ss

wavy---------Ss x wavy---------Ss

offsprings

straight,-------SS--------25%

wavy---------Ss-------------50%

curly,--------ss--------25%

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