Not entirely sure how to approach this problem, because went over very little se

Question

Not entirely sure how to approach this problem, because went over very little sex-influended traits in the class.

Hornless trait in sheep is dominant in males and recessive in females; this phenomenon is known as sex-influenced traits. Prove that you understand the difference between sex-influenced traits determined by autosomal genes and sex linkage. Predict F1 and F2 in both reciprocal crosses of pure-bred horned (e.g., Dorset) and pure-bred hornless (e.g. Suffolk). Use the table provided. Indicate what's the most striking difference between the predictions of sex-influenced and sex-linked hypotheses.

Explanation / Answer

H+ is dominant and H is recessive

Sex influenced traits are autosomal where genes are not present in the sex chromosome.

a) Sex infuenced

Horned ewe (female) x hornless ram (male)

H+H+ x HH

F1: H+H : males - horned

F1: H+H : females - hornless

F2 : H+H x H+H

H+H+, HH+, H+H, HH

Males : 3 horned and 1 hornless

Females: 3 hornless and 1 horned

b) Sex influenced

Hornless ewe (female) x horned ram (male)

HH x H+H+

F1: H+H

Males : horned

Females : hornless

F2 : H+H x H+H

H+H+, HH+, H+H, HH

Males : 3 horned and 1 hornless

Females: 3 hornless and 1 horned

c) Sex linked

Sex linked means that genes are present in the sex chromosome that is either on X or Y chromosome. Here it is X-linked as it is dominant in males with single allele

Horned ewe (female) x hornless ram (male)

H+H+ x HH

F1: H+H

Male : horned because only one X chromosome carriers H+ as males have XY

Female: Hornless because only one X chromosome carriers H+ and another X has H.

Same is followed in F2 and also in the cross Hornless ewe (female) x horned ram (male)

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