hs experiments with pea plants, Mendel considered other independent traits along

Question

hs experiments with pea plants, Mendel considered other independent traits along of pea colour and texture. One of these traits was flower colour which could be eithe white (w) or purple (p). Suppose that white dominates purple; green dominates yellow and smooth dominates wrinkled. Construct the heredity diagram for the second generation of a cross of the two pure line strains SGp and WYw, assuming reproduction by selfing after the first filial generation. Include the expected proportions of each second generation combination of traits. (8 pts)

Explanation / Answer

Consider the following genes for the given phenotype (upper case letters denote dominant allele while lower case letters denote recessive alleles)

W= White

w = purple

G = green

g = yellow

S = Smooth(round)

s = wrinkled

Since true breeding strains are homozygous,

Thus genotype of SGp (Parent 1) = SSGGww

Gamates produces = only one type containg SGw

And genotype of WYw (Parent 2) = ssggWW

Gamates produces = only one type containg sgW

Crossing the parents

(Parent 1)                            x             (Parent 2)

    SGw                                                     sgW

Phenotype: all F1 generation will be smooth, green seeds with white flowers

Thus F1 generation genotype will be SsGgWw

Gamates produced: SGW, SGw, SgW, Sgw, sGW, sGw, sgW, sgw

Self-crossing F1 generation, the F2 generation will be

                                                                                           

SGW

SGw

Sgw

SgW

sGW             

sGw        

sgW

sgw

SGW

SSGGWW

SSGGWw

SSGgWw

SSGgWW

SsGGWW

SsGGWw

SsGgWW

SsGgWw

SGw

SSGGWw

SSGGww

SSGgww

SSGgWw

SsGGWw

SsGGww

SsGgWw

SsGgww

Sgw

SSGgWw

SSGgww

SSggww

SSggWw

SsGgWw

SsGgww

SsggWw

Ssggww

SgW

SSGgWW

SSGgWw

SSggWw

SSggWW

SsGgWW

SsGgWw

SsggWW

SsggWw

sGW  

SsGGWW  

SsGGWw  

SsGgWw  

SsGgWW  

ssGGWW  

ssGGWw

ssGgWW  

ssGgWw  

sGw

SsGGWw

SsGGww

SsGgww

SsGgWw

ssGGWw

ssGGww

ssGgWw

ssGgww

sgW

SsGgWW

SsGgWw

SsggWw

SsggWW

ssGgWW

ssGgWw

ssggWW

ssggWw

sgw

SsGgWw

SsGgww

Ssggww

SsggWw

ssGgWw

ssGgww

SsggWw

ssggww

The F2 generation,

Phenotypic ratio:

27: Smooth, green and white flower

9: Smooth, green and purple flower

9: Smooth, yellow and white flower

3: Smooth, yellow and purple flower

9: wrinkled, green and white flower

3: wrinkled, green and purple flower

3: wrinkled, yellow and white flower

1: wrinkled, yellow and purple flower

Genotypic ratio:

1: SSGGWW

2: SSGGWw

1: SSGGww

2: SSGgWW

4: SSGgWw

2: SSGgww

1: SSggWW

2: SSggWw

1: SSggww

2: SsGGWW

4: SsGGWw

2: SsGGww

4: SsGgWW

8: SsGgWw

4: SsGgww

2: SsggWW

4: SsggWw

2: Ssggww

1: ssGGWW

2: ssGGWw

1: ssGGww

2: ssGgWW

4: ssGgWw

2: ssGgWw

1: ssggWW

2: ssggWw

1: ssggww

SGW

SGw

Sgw

SgW

sGW             

sGw        

sgW

sgw

SGW

SSGGWW

SSGGWw

SSGgWw

SSGgWW

SsGGWW

SsGGWw

SsGgWW

SsGgWw

SGw

SSGGWw

SSGGww

SSGgww

SSGgWw

SsGGWw

SsGGww

SsGgWw

SsGgww

Sgw

SSGgWw

SSGgww

SSggww

SSggWw

SsGgWw

SsGgww

SsggWw

Ssggww

SgW

SSGgWW

SSGgWw

SSggWw

SSggWW

SsGgWW

SsGgWw

SsggWW

SsggWw

sGW  

SsGGWW  

SsGGWw  

SsGgWw  

SsGgWW  

ssGGWW  

ssGGWw

ssGgWW  

ssGgWw  

sGw

SsGGWw

SsGGww

SsGgww

SsGgWw

ssGGWw

ssGGww

ssGgWw

ssGgww

sgW

SsGgWW

SsGgWw

SsggWw

SsggWW

ssGgWW

ssGgWw

ssggWW

ssggWw

sgw

SsGgWw

SsGgww

Ssggww

SsggWw

ssGgWw

ssGgww

SsggWw

ssggww

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