Question

Please explain these in a way that makes sense as soon as possible

1. Two different autosomal loci (t1 and t2) can render a mouse tailless. The tailless alleles at both loci are recessive. Homozygosity for the recessive allele at either of the loci or at both loci renders the mouse tailless. A tailless mouse homozygous for t1 is mated to a tailless mouse that is homozygous for t2 and produces F1 mice with NORMAL tails. What will be the ratio of tailed: tailless mice in the F2 ? 1 E e. 9:7 c. 12:4 d. 13:3 b. 3:1 a. 7:1 Vinca (the periwinkle family) have a height determined by polygenes. The shortest Vinca grow to a full height of only 3 inches, while the largest Vinca is 27 inches high at maturity. If one crosses a 3 inch Vinca and a 27 inch Vinca, 15 inch Vinca result. If the F1 are allowed to interbreed, then one gets a range of plants from 3 to 27 inches high. However, one only obtains about one plant in 256 that is 3 inches high, and only about one plant in 256 that is 27 inches high. 2.D 2. How many loci are involved in height determination in Vinca? d. 4 f. 6 e. 5 g 8 b. 2 c. 3 a. 1 3. C 3. What is the contribution per contributing allele? b. 2 inches d. 4 inches e. 6 inches a. 1 inch c.3 inches 4 E 4. From the F1 x F1 cross, what is the probability of observing 24 inch Vinca plants? c. 56/256 d. 4/256 e. 8/256 a. 1/256 b. 28/256 5 B 5. If a 15 inch F1 Vinca is crossed with a 3 inch Vinca, how frequently will a 6 inch Vinca result? a. 1/16 b. 4/16 d. 4/256 e. 8/256 c. 6/16 6. Two races of corn averaging 48 and 96 inches in height respectively are crossed. The F1 is quite uniform averaging 72 inches tall. The F1 plants are self-fertilized to give an F2. Of 512 F2 plants only two are as short as 48 inches and two are as tall as 96 inches. How many polygene ALLELES are 6 C involved in this trait? c. 8 d. 5 b. 4 e. 6 a. 3 7. How much does each contributing allele contribute to height in corn? 7 B d. 4 inches b. 6 inches c. 3 inches e. 1 inch a. 8 inches 8. Of 512 F2 plants, how many will be 78 inches tall? b. 112 8. B c. 163 d. 228 e. 32 a. 56 9.One type of roan color in horses is fully dominant over normal solid color and results in the presence of white hairs interspersed among the solid color hairs. The locus for one type of paint in horses (Overo paint) is fully dominant, but when homozygous the Overo allele is lethal. Both loci are autosomal. Two roan and paint horses that are heterozygous for roan and heterozygous for Overo paint horse? Consider only living progeny. were crossed. What is the probability that their first offspring is also a roan and paint 9 B b. 1/2 a. 3/8 c. 5/12 d. 8/12 e. 9/16

Answer 1

1. Option E is correct.
Parental cross: t1t1T2T2 X T1T1t2t2
F1 progeny: T1t1T2t2
F1 selfing: T1t1T2t2 X T1t1T2t2
F2 progeny phenotypic ratio = 9:7
T1_T2_ = Tailed = 9
T1_t2t2 = Tailless = 3
t1t1T2_ = Tailless = 3
t1t1t2t2 = Tailless = 1

2.
Shortest = aabbccdd = 3 inches
Largest = AABBCCDD = 27 inches
Parental cross: aabbccdd X AABBCCDD
F1 progeny: AaBbCcDd
Number of genes = 4 (Each with two alelles)
Contribution from each dominant allele = 3 inches
24 inches = The presence of one recessive allele = 8/256

15 inches = AaBbCcDd
3 inches = aabbccdd
Parental cross: AaBbCcDd X aabbccdd
6 inches = The presence of one dominant allele = 8/256