Answer:
3/4 taster; 1/4 non-taster
The likelihood that their first child will be a taster: 75 %
Explanation:
Complete dominance occurs when a dominant gene variant or 'allele' completely masks the expression of the recessive allele in heterozygous individuals (i.e., individuals carrying one copy of the dominant allele and one copy of the recessive allele). In this case, both parents are heterozygous for a single gene trait (i.e., the ability to taste) which is ruled by complete dominance. In consequence, the expected phenotypic ratio in the progeny (F1) will be:
- Alleles: T (dominant taster allele); t (recessive non-taster allele)
- Parental cross: Tt x Tt
- Punnett Square from this cross:
T t
T TT Tt
t Tt tt
Expected F1 phenotypic ratio: 3/4 taster (i.e., 1/4 TT genotype + 1/2 genotype Tt = 3/4 or 75%); 1/4 non-taster (tt genotype = 1/4 or 25%). Moroever, the chance that the first child has the taster phenotype is 3/4 (75%).
Answer:
Genotypic ratio of offsprings will be: 1 (Hh) : 1 (hh)
Explanation:
This question involves a single gene coding for the possession or not of Hitchhiker's thumb in humans. The allele that codes for Hitchhiker's thumb (H) is dominant over the allele for no hitchhiker's thumb (h).
Based on this question, if woman who does not have hitchhiker's thumb (hh) marries a man who is heterozygous for hitchhiker's thumb (Hh) i.e. hh × Hh, the following gametes will be produced by each parent:
hh - h and h
Hh - H and h
Using these gametes in a punnet square (see attached image), the offsprings with the following genotypic ratio will be likely produced:
1 (Hh) : 1 (hh)
N.B:
- Two (2) of them were Hh i.e. with Hitchhiker's thumb
- The other two were hh i.e. no hitchhiker's thumb.
Two parent mice with black fur have offspring with white hair.
Since both are heterozygous, that means they both have a dominant and recessive allele, but since they have a dominant, that trait is displayed. Since both also have a recessive allele, there is a possibility that they can have offspring with a recessive trait.
In other words, if you have 2 heterozygous parents that show a dominant allele, offspring that display the recessive allele is possible.
Hope this helps :)
