23. In a cross between AABbCcDD and AaBbecdd, what proportion of the offspring w

Question

23. In a cross between AABbCcDD and AaBbecdd, what proportion of the offspring wou be expected to be A B C_D ? (4_ means AA or Aa.) A) 3/256 B) 3/32 C) 3/16 D) 3/8 E) 3/4 in the next A) AA x AA B) AA x aa C) Aa x Aa E) aa x aa 25. Round seeds (R) are dominant to wrinkled seeds (), and yellow seeds (1) are dominant to green seeds (v). A true-breeding pea plant with round and yellow seeds is crossed toa true-breeding plant with wrinkled and green seeds. The Fi progeny are allowed to self- fertilize. What is the probability of obtaining a yellow seed in the F2? A) 3/4 ) 1/16 C) 9/16 D) 3/16 E) 1/2 26. In dogs, black coat color (B) is dominant over brown (b), and solid coat color (S) is dominant over white spotted coat (s). A cross between a black, solid female and a black, solid male produces only puppies with black, solid coats. This same female was then mated with a brown, spotted male. Have of the offspring from this cross were black and solid, and half of the offspring were black and spotted. Which of the following could be the genotype of the black, solid male? A) BBSs B) BBss C) Bbss D) Bbss E) Bbss 27. What is the difference between a backcross and a testcross?

Explanation / Answer

24.D) is the answer- Aa × aa gives Aa,Aa,aa,aa which gives phenotypic ratio 1:1

25.A)The F1 generation obtained after crossing is YyRr which is obtained from parents YYRR and yyrr.

The F2 generation obtained by self fertilization of YyRr gives four progeny with following frequency:

Yellow and round:9/16

Yellow and wrinkled:3/16

Green and round:3/16

Green and wrinkled:1/16

there fore total number of yellow seeds is 9+3/16=12/16=3/4

27.Back cross: 1. It is the cross of hybrids of F1 generation with either of the parents .Which means either with a dominant parent or a recessive parent.

2.Back crosses recovers the elite genotypes.

  Test cross: 1.A type of back crosd but specific to the recessive parent.Crossing of a F1 generation hybrid offspring with its homozygous recessive parent is known as test cross.

2.Test cross identifies the zygosity of the dominant phenotype.

Q. no 23 and 26 are not answered due to small amount of confusion.

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