Question

Professor Borisandnatashavitch of the University of Northern Siberia has discovered a previously unknown population of Siberian beaver. Several unusual traits are present in this population of beaver; some individuals have erect ears while others have bent ones. After Dr. Borisandnatashavitch conducted extensive research on this population, he found that (1) it was a sex-linked trait, and (2) the allele for erect ears was dominant to that for bent ears. When Dr. Borisandnatashavitch returned to his lab in Popoffatthemouth, USSR, he brought back a male beaver with bent ears and a female with erect ears. He allowed these two animals to breed, and over a period of several years they produced a total of 58 offspring; 32 of these were female, while 26 were male. All of the offspring, regardless of sex, had erect ears. Because Dr. Borisandnatashavitch does not receive much money from the central government, he cannot afford to do genetic test on all of these animals to determine their genotypes. Please assist him by determining the genotypes of the parents and all of the offspring. Express the genotypes both symbolically and in words.

Answer 1

Since all the offsprings have errect ears which is a dominant trait, the female parent must be homozygous dominant of erect ears. ( because if female was heterozygous the progeny could be with bent ears as the male parent was with bent ears )

(if E-errect and e-bent ears ; since it is sex linked charecter is dominated and transmitted by X chromosome)

Genotype of female parent: X^EX^E  ( Homozygous Dominant with errect ears)

Genotype of male parent: X^eY⁰ ( Heterozygotes with bent ears)

Genotype of female offsprings: X^EX^E ( homozygous dominant with errect ears) or X^EX^e(Heterozygous with dominant alleles)

Genotype of male offsprins: X^EY⁰ ( Heterozygotes with errect ears)