In domestic chickens, sex is determined by the ZW system. A Z-linked gene determ
ID: 23712 • Letter: I
Question
In domestic chickens, sex is determined by the ZW system. A Z-linked gene determining feather formation has two alleles: F produces fast feathering, and f produces slow feathering. Give the genotypes of parental and progeny male (rooster) and female (hen) chickens for the following crosses:Part A:
Parents: fast-feathering rooster x fast-feathering hen.
Progeny: Roosters are fast-feathering, hens 1/2 slow-feathering and 1/2 fast-feathering.
A) Parents: the rooster f W,the hen Ff . Progeny: male 1/2 Ff and 1/2 ff, female 1/2 FW and 1/2 f W.
B) Parents: the rooster Ff , the hen f W. Progeny: male 3/4 Ff and 1/4 ff, female 3/4 FW and 1/4 f W .
C) Parents: the rooster Ff, the hen FW. Progeny: male 1/2 Ff and 1/2 FF, female1/2 FW and 1/2 f W.
D) Parents: the rooster ff , the hen f W. Progeny: male 1/2 Ff and 1/2 ff, female 1/2 FW and 1/2 f W.
E) Parents: the rooster Ff , the hen f W. Progeny: male 1/2 Ff and 1/2 ff, female 1/2 FW and 1/2 f W.
F) None of all above.
Part B
Parents: slow-feathering rooster x fast-feathering hen.
Progeny: All roosters are fast-feathering; all hens are slow-feathering.
A)Parents: the roosters FF, the hen fW. Progeny: male all Ff, female all FW.
B) Parents: the roosters ff , the hen FW. Progeny: male all Ff, female all fW.
C) Parents: the roosters ff , the hen FW. Progeny: male all ff, female all FW.
D) Parents: the roosters FW, the hen ff . Progeny: male all Ff, female all fW.
E) Parents: the roosters ff , the hen FW. Progeny: male 1/2 Ff, 1/2 f f, 1/2 FW and 1/2 f W.
F) None of all above.
Explanation / Answer
Part A.
Let roosters are homozygous for ZZ, and heterozygous for feather formation allele. Therefore, the following are the genotypes of the parents:
Rooster: ZF Zf
Hen: ZF W
The following is the inheritance in the offspring:
Female gametes
Male gametes
ZF
W
ZF
ZF ZF
ZF W
Zf
ZF Zf
Zf W
The progeny have the following genotypes:
Roosters: ½ FF and ½ Ff, hens (female): ½ FW and ½ fW
Therefore, the correct answer is c. C) Parents: the rooster Ff, the hen FW. Progeny: male 1/2 Ff and 1/2 FF, female1/2 FW and 1/2 f W.
Part B:
Roosters: Zf Zf
Hen: ZF W
Progeny:
Female gametes
Male gametes
ZF
W
Zf
ZF Zf
Zf W
Zf
ZF Zf
Zf W
Therefore, the correct answer is B) Parents: the roosters ff , the hen FW. Progeny: male all Ff, female all fW
Female gametes
Male gametes
ZF
W
ZF
ZF ZF
ZF W
Zf
ZF Zf
Zf W
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