3.Among Urepian Rock-things, skin texture is determined by a single autosomal ge

Question

3.Among Urepian Rock-things, skin texture is determined by a single autosomal gene. The wild type allele of this gene (th+) codes for hard, scale-like skin, whereas a mutant allele (th) codes for soft, smooth skin. When a Rock-thing with hard skin is crossed with a Rock-thing whose phenotype is soft, smooth skin, only smooth, soft-skinned offspring are ever observed. One possible answer is that: (Hint: For each answer, see if the offspring phenotypes are consistent the parental matings).

A. the parental Rock-thing with the soft, smooth skin is homozygous at the gene and the th allele is dominant.

B. the parental Rock-thing with the hard skin is heterozygous for the gene and the th+ allele is dominant.

C. the parental Rock-thing with the soft, smooth skin is heterozygous at the gene and the th+ allele is dominant.

D. neither allele is dominant

Explanation / Answer

The correct option is ...........................A. the parental Rock-thing with the soft, smooth skin is homozygous at the gene and the th allele is dominant.

th+ (wild)........... codes for hard, scale-like skin

th(mutant).............. codes for soft, smooth skin

parental cross: thth x th+th+

Offsprings: th (soft, smooth skin), all are soft,smooth skin, shows 'th' is dominant.

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