In a cross between an individual who is RrPp and one who is

In a cross between an individual who is RrPp and one who is rrpp, the following offspring are obtained: 27 RrPp 21 rrrp 25 Rrpp 20 Rrpp a) Are the R and P genes linked to each other? How do you know? b) Are the R and P genes on the same chromosome as each other? In a series of crosses to look at the relationship of different genes with each other, the following crosses were performed. The numbers of offspring obtained from each cross are shown. a) For each one. note whether the genes are linked, and if so how closely (in mu); and whether the alleles are present in coupling or repulsion in the heterozygous parent. b) Which genes are most tightly linked (closest together on the same chromosome)?

Solution

3. a) As the genotypes are showing 1:1:1:1 ratio, those are not linked genes.

For further conformation adopting chisquare test

Null hypothesis: The observed values are not deviating form the Expected 1:1:1:1 ratio.

Category

RrPp

rrpp

Rrpp

rrPp

Total

Observed values

27

21

25

20

93

Exptected Ratio

1

1

1

1

4

Exprected Values

23.25

23.25

23.25

23.25

Deviation

3.75

-2.25

1.75

-3.25

D^2

14.0625

5.0625

3.0625

10.5625

D^2/E

0.604839

0.217742

0.13172

0.454301

1.408602

X^2

1.408602

Degrees of freedom

4-1

3

Inference: The calculated chi square value is lessthan the table value @ 3 DF and 0.05 probability i.e. 7.815, Hence null hypothesis accepted.

b) As the genes are showing independent assortment, which means both genes are present on same chromosome.

According to chegg guidelines we have to answer one question at a time, so post the other question as sperate question then I can help you.

Category	RrPp	rrpp	Rrpp	rrPp	Total
Observed values	27	21	25	20	93
Exptected Ratio	1	1	1	1	4
Exprected Values	23.25	23.25	23.25	23.25
Deviation	3.75	-2.25	1.75	-3.25
D^2	14.0625	5.0625	3.0625	10.5625
D^2/E	0.604839	0.217742	0.13172	0.454301	1.408602
X^2	1.408602
Degrees of freedom	4-1	3