Tribble fur is Brown (B) or white (b) Tribble tend to be quiet (Q) or loud (q) T

Question

Tribble fur is Brown (B) or white (b)

Tribble tend to be quiet (Q) or loud (q)

Tribbles can have large Noses (N) or small ones (n)

Parental: Pure breeding Brown, Big nosed, Quiet trribles x pure breeding white, small nosed, loud tribble

F1: 100 % Brown, Big nosed, and Quiet

Backcross the F1 to the pure recessive parent yeilds >>>>

113 small nosed loud tribbles, 4 small nosed tribbles, 300 completely wild type, 113 white tribbles, 23 white small nosed triibles, 7 white loud tribbles, 318 white small nosed loud tribbles, 22 big nosed, brown, loud tribbles.

What are the genotpyes of P, F1, F2 progeny, and which gene is in the middle?

Please explain, Thanks in advance!

Explanation / Answer

1. According to the give data Tribble dominant characters are brown, big nose, and quit (BQN), and recessive characters white, small nose and loud (bqn).

2. The pure breeding parents of Brown,Big nosed, Quit (BQN/BQN) is crossed with pure breeding white, small nosed, loud (bqn/bqn)

3. So we get the F1 generation with BQN/bqn all of them af brown big nosed quit.

4. If the F1 is test crossed 8 different characteristics off-springs are produced. The genotype of these are as follows given below.

Pure breed parents BQN/BQN X bqn/bqn

F1 generation BQN/bqn   

F1 Test cross BQN/bqn X bqn/bqn

Parental types: Brown,Big nose, Quit (BQN) = 300

White, Small nose, Loud (bqn) = 318

Single cross over; White tribbles (bNQ) = 113

Small nose, loud tribbles (Bnq) = 113

White small nose (bnQ) = 23

Big nose, brown, loud (BNq) =22

Double cross over:Small nosed tribbles (BnQ) = 4

White loud tribbles (bnQ) = 7

5. As compared to genotype of double cross over, over the parental genotype one of the gene flips. From the above gene B/b flips that leads to double cross. The frequency of double cross over will be less in number.

6. The gene which flips will be in the middle of the sequence. So the correct sequency of the gene is NBQ/NBQ and nbq/nbq.

7. Finally the gene B/b is in the middle.

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