A cucumber plant that produces red flower and spherical frui

A cucumber plant that produces red flower and spherical fruit is crossed with a plant that produces white flower and long fruit. All the F_1 have pink flower and long fruit. When the F_1 are intercrossed, F_2 progeny are produced with the following phenotypes and numbers: 90 pink flower and long fruit 45 red flower and long fruit 45 white flower and long fruit 40 pink flower and spherical fruit 30 pink flower and short fruit 20 red flower and spherical fruit 20 white flower and spherical fruit 15 red flower and short fruit 15 white flower and short fruit Provide the most likely genetic explanation for the results and assign genotypes of: Parental red flower and spherical fruit cucumber: Parental white flower and long fruit cucumber: F_1 progeny: F_2 pink flower and spherical fruit progeny: Among those twenty F_2 plants with white flower and spherical fruit, how many would be breed true? Briefly explain and circle your answer.

Solution

a)

Genotype of parent with red flower and spherical fruit is RRss

b)

Genotype of parent with white flower and long fruit is rrSS

c)

Genotype of F1 offspring with pink flower and long fruit is RrSs

d)

Genotype of F2 pink flower and sphreical fruit progeny is Rrss

rrss

(white flower and

spherical fruit)

e)

The F2 individuals are obtained in 9:3:3:1 ratio. Among 20 F2 plants with white and spherical fruit (rrss) = 20 x1/16 = 5/4 = 1.25% are true breeding with genotype rrss.

male/ female	RS	Rs	rS	rs
RS	RRSS	RRSs	RrSS	RrSs
Rs	RRSs	RRss	RrSs	Rrss
rS	RrSS	RrSs	rrSS	rrSs
rs	RrSs	Rrss	rrSs	rrss (white flower and spherical fruit)