4. In a certain breed of plants, thorns are determined by the dominant allele, T
ID: 132548 • Letter: 4
Question
4. In a certain breed of plants, thorns are determined by the dominant allele, T, and thornless is determined by the recessive allele, t-T is 80% penetrant in the heterozygote. In the monohybrid cross Tt X Tt, what would be the expected ratio of phenotypes observed in a population of 500 progeny plants? A. 325 thomy: 175 thornless B. 100 thorny: 400 thornless C. 175 thorny: 325 thornless D. 400 thomy: 100 thornless E. 25 thorny: 475 thornless 5. In chickens, the dominant allele of one gene (R) determines a rose comb shape and the dominant allele of a different gene (P) determines pea comb shape. If at least one dominant allele of both genes is present, a walnut comb shape is observed. The recessive alleles of each gene, when present together in a homozygous state, give a "single comb" shape. Rose-combed chickens are mated with walnut combed chickens and the following progeny are observed: 15 walnut-combed chickens 14 rose-combed chickens 5 pea-combed chickens 6 single-combed chickens The genotypes of the birds used in this cross was: A. RRpp X RrPp B. RrPp X RrPp C. Rrpp X RrPp D. Rrpp X RRPP E RRPP X rrppExplanation / Answer
4) In a monohybrid cross between the two heterozygotes, the expected phenotypic ratio is 3:1 and the genotypic ratio is 1:2:1. The dominant allele is 80% penetrant in the heterozygote.
There are 500 offsprings. Of them, 125 will be homozygous dominant, 250 will be heterozygous and the remaining 125 will be homozygous recessive. It is given that the dominant allele is 80% penetrant in the heterozygotes. So, out of 250 heterozygotes 200 will express the dominant allele.
The dominant trait will be expressed in TT (125) and Tt (200) offsprings. Thornless trait is observed in tt (125) and Tt (50) individuals. So, in total 325 offsprings will be thorny and 175 thornless (option A).
Please post other question separately.
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.