GENETICS Please show all work so I can fully understand. Thank you so much 4. In
ID: 132085 • Letter: G
Question
GENETICS
Please show all work so I can fully understand. Thank you so much
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 thorny: 175 thornless C. 175 thorny: 325 thornless D. 400 thorny: 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 rippExplanation / Answer
4.
When Tt xTt where T = thorns and t= thornsless
It gives
T
t
t
Tt
tt
T
Tt
Tt
It gives 3:1 ratio of phenotypes i.e. 3thorns and 1 thornless out of 4 plant
Out of 500 plants 400 will thorny and 100 will be thornless
5.
Given phenotype
Rose comb = RrPp
Pea comb= RrPp
Walnut comb= RRPP
Single comb=rrpp
Given cross is
Rose comb x walnut comb
RrPp x RrPp
RP
rp
RP
RRPP
RrPp
rp
RrPp
rrpp
Given phenotype in 1:1:1:1 ratio
Here also in1:1:1:1 ratio so that option B is answer
T
t
t
Tt
tt
T
Tt
Tt
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