Question

In tomatoes, tall growth habit is the result of a dominant gene, D. Dwarf growth to its recessive allele, d. Smooth epidermis is due to a dominant gene P pubescent epidermis to its recessive allele p. a homozygous tall smooth vaiety was crossed with a dwarf pubescent variety, the f1 were testcrossed to dwarf pubescent. the results of the test cross were as follows.
tall, smooth-96

tall, pubescent-4

dwarf, smooth-3

dwarf pubescent-95

Are these genes linked? If so, what is the percent of crossing over?

Answer 1

Answer:

RF= 3.535%

Explanation:

Given;

Tall (D) is dominant over dwarf growth (d);

Smooth (P)  is dominant over pubescent epidermis(p).

Cross between homozygous tall, smooth( DDPP) and dwarf pubescent (ddpp);

= DDPP × with ddpp

F1 = DdPp (tall, smooth).

As given; F1  (DdPp) were crossed with dwarf pubescent (ddpp);

DdPp × ddpp

Progeny as given,

are=

tall, smooth (D_P_) -96;

tall, pubescent (T_pp) - 4;

dwarf, smooth (ddD_) - 3;

dwarf,pubescent ( ddpp)- 95.

Recombinants are= 3+4= 7

non-recombinants = 95+94= 191

Yes, these genes are linked genes.

Recombination frequency= total recombinants/ total progeny× 100

= 7/198× 100=3.535

So RF= 3.535%