I. Black and yellow coat color in cats is known to be controlled by an X-linked locus. The two alleles at that locus are XB and Xb.
Females homozygous for the recessive Xb allele ( Xb/Xb ) are yellow. Females homozygous for the dominant XB allele ( XB/XB ) are black. Females heterozygous at that locus ( XB/Xb ) are mottled yellow and black, or "calico".
Male cats are normally either yellow ( Xb/Y ) or black ( XB/Y ). Male calico cats do occur but they are very rare and always sterile.
A black female cat, whose mother and father were black, was mated with a yellow male cat, whose mother was yellow and father was black. They had two kittens; one kitten was a female and the other was a male. Surprisingly, both the female kitten and the male kitten were calico.
A. What are the genotypes of the parents of the two kittens?
B. What is the genotype of the female calico kitten?
C. What is the genotype of the male calico kitten?
Females homozygous for the recessive Xb allele ( Xb/Xb ) are yellow. Females homozygous for the dominant XB allele ( XB/XB ) are black. Females heterozygous at that locus ( XB/Xb ) are mottled yellow and black, or "calico".
Male cats are normally either yellow ( Xb/Y ) or black ( XB/Y ). Male calico cats do occur but they are very rare and always sterile.
A black female cat, whose mother and father were black, was mated with a yellow male cat, whose mother was yellow and father was black. They had two kittens; one kitten was a female and the other was a male. Surprisingly, both the female kitten and the male kitten were calico.
A. What are the genotypes of the parents of the two kittens?
B. What is the genotype of the female calico kitten?
C. What is the genotype of the male calico kitten?
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A. What are the genotypes of the parents of the two kittens?
Female is XB/XB and male is Xb/Y
B. What is the genotype of the female calico kitten? XB/Xb
C. What is the genotype of the male calico kitten? XB/XbY.
This is because of non-disjunction in sperm, so he produces trisomy sperm XbY. When this sperm fertilizes XB egg it produces XB/XbY. As you said, it is very rare and the male calico kitten is sterile.
Female is XB/XB and male is Xb/Y
B. What is the genotype of the female calico kitten? XB/Xb
C. What is the genotype of the male calico kitten? XB/XbY.
This is because of non-disjunction in sperm, so he produces trisomy sperm XbY. When this sperm fertilizes XB egg it produces XB/XbY. As you said, it is very rare and the male calico kitten is sterile.