Question

Traits Tribbles make two noises- they Purr (P) or they Coo (p)

Tribble hair is Long (H) or short (h)

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

Tribbles have Long Legs (L) or short legs (l)

Tribbles tend to be Quiet (Q) or loud (q)

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

Tribbles can be Fast (F) or slow (f).

Cross #1 P: Pure breeding fast, long haired, purring tribble x pure breeding slow, short haired, cooing tribble

F1: 100% fast, long haired, purring tribbles

Backcross between the F1 and the cooing parent yields the following tribbles

25 Purring, Fast, Long Haired

25 Purring, slow, short haired

25 Purring, fast, short haired

25 Purring, slow, long haired

25 Cooing, fast, long haired

25 cooing, slow, short haired

25 cooing, fast, short haired

25 cooing, slow, long haired

1. Diagram out each cross including the Parental, F1, and F2 generations. Label each individual (genotype and phenotype) and indicate linkage (by diagraming the chromosomes) where necessary.

Answer 1

The F1 cross is: FFHHPP X ffhhpp

F1 result: FfHhPp

F2 cross is: FfHhPp X ffhhpp

Result:

There will be total 8 genotypes: 2^{(alleles-genes)} = 2^(6-3) = 8

1:1:1:1:1:1:1:1 ratio.

Labelling of each individual:

1. 25 Purring, Fast, Long Haired (P_F_H_)
2. 25 Purring, slow, short haired (P_ffhh)
3. 25 Purring, fast, short haired (P_F_hh)
4. 25 Purring, slow, long haired (P_ffH_)
5. 25 Cooing, fast, long haired (ppF_H_)
6. 25 cooing, slow, short haired (ppffhh)
7. 25 cooing, fast, short haired (ppF_hh)
8. 25 cooing, slow, long haired (ppffH_)

Please note that there is no linkage in this back cross. If there had been linkage, then the number of parental types should be greater than the number of recombinants. But here all genotypes are equal. This means that no genes are linked.

So, the diagramming of chromosomes (for linkage) is not possible here.

**Note: For diagrams of each cross, each part should be posted separately.