A metallic blue-colored Indian blue peahen with long pinion feathers is crossed
ID: 142446 • Letter: A
Question
A metallic blue-colored Indian blue peahen with long pinion feathers is crossed with a dull brown-colored Indian blue peacock with short pinion feathers. Half of the resulting peacocks are metallic blue with short pinions and half the resulting peacocks are metallic blue with long pinions. Half of the resulting peahens are dull brown with short pinions and half the peahens are dull brown with long pinions. Long pinions are the result of a functional protein. A) Which gene is sex-linked? B) What are the genotypes of each parent and each type of offspring?
Is the correct way to do this? Can you please do punnett square and give a key Thank you very confused
Key
Blue color - B
Dull brown color - b
Long pinion feathers L
Short pinion feathers - l
Genotypes of parents
Metallic blue-colored Indian blue peahen (female) with long pinion feathers = ZW BbLl
Dull brown-colored Indian blue peacock(male) with short pinion feathers = ZZ bll
Genotypes of offspring
Metallic blue short pionion peacock = ZZ Bll
Metallic blue long pinion peacock = ZZ BLl
Dull brown short pinion peahen = ZW bbll
Dull brown long pinion peahen = ZW bbLl
Please do punnett square Sex-linked trait would be color. why?
Explanation / Answer
The Z chromosome is known to contain all the sex linked genes. W chromosome like Y chromosome in humans does not contains genes.
Only males are showing the dominant phenotype as they receive two copies of Z chromosomes, one from mother and other from father. If colour is sex linked then all males must be dominant blue phenotype as they recieve a dominant copy from mother which is able to mask the recessive copy received from father. If pinion length was sex linked then all males must have long pinions. However this is not observed.
Also all the females are dull brown. If colour is sex linked then they receive this trait only from Z chromosome received from father who have the genotype bbll. The W chromosome they receive from mother do not have any gene. Females(ZW) are hemizygous like males (XY) in human system. If pinion length was sex linked then all the female progeny would be having short pinion which is not the case.
Therefore colour is the sex linked trait
Parental cross : (female ) ZBW X (male) Zb Zb
Progeny : ZBZb (blue male) Zb W (dull brown female)
Another trait pinion length is autosomal and the genotype of the parents are Ll and ll. because male is having short pinion (recessive) which can only be expressed in homozygous conditon. The female should be Ll as progeny are having both long and short pinion.
Ll x ll
progeny : Ll (long pinion) , ll (short pinion)
These are autosomal traits and can be transmiited equally to either sex.
So ZBZb (blue male) can inherited Ll (long pinion) to produce metallic blue male with long pinion
ZBZb (blue male) can also inherited ll short pinion) to produce metallic blue male with short pinion
ZbW (Dull brown female) can inherited Ll (long pinion) to produce dull brown female with long pinion
ZbW (Dull brown female) can inherited ll (short pinion) to produce dull brown female with short pinion