A homozygous plant with 20 cm diameter flowers is crossed with a homozygous plan

Question

A homozygous plant with 20 cm diameter flowers is crossed with a homozygous plant of the same species with 40 cm diameter flowers.  The F1 plants all have 30 cm diameter flowers. In the F2 generation (N=512 plants), 2 plants have 20 cm diameter flowers and 2 plants have 40 cm diameter flowers.  The rest of the plants have flowers ranging in sizes in between 20-40 cm in diameter.

(a) What frequency distribution of flower diameter do you expect to see in the F2 generation?

(b) What frequency distribution of flower diameter do you expect to see in the progeny of backcross between an F1 plant and the 40 cm diameter flowered parent?

explain the answers please. thank you

Explanation / Answer

This is a quantitave situation as we are dealing with diameter of the flower , polygenic traid.

Given basic size of the flower & total number of alleles dominant nature in the traid.

A- F2 generation show (4 phenotype) given , n= 512 - 4 = 508  

2 plants showing 40 cm in diameter

so, 2 /508= 1/ 254 ( pretty close to 256 ( 4*4*4*4) )

total gene involve in traid = 4 n=4

now , bais flower size = 20 cm given with total 4+4 alleles = 20/8 = 2.5 cm flower

therefore,frequency distribution of flower diameter in F2 generation= 2.5 cm

b- If you backcrossF1 plant with 40 cm diameter flower than

we will see 5 phenotypes

1- 40 cm

2- 37.5cm

3- 35cm

4- 32.5cm

5- 30cm

with difference of 2.5 cm

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.