3. Multiple Crosses: You are a tomato gardener! Characters that you are interest

Question

3. Multiple Crosses: You are a tomato gardener! Characters that you are interested in

influencing include: fruit color (red is dominant to yellow); viney (lots of vines are dominant

to not a lot of vines), and ripening (ripe before picked is recessive to ripe after picked). Of

course all characters are controlled by a single gene and have only 2 possible traits.

a. Devise a lettering system for each character based on the information given.

b. You cross a dominant true breed to a recessive true breed for all characters.

i. List the genotypes and phenotypes of each parent and all possible

combinations of gametes.

ii. List the genotype and phenotype of the F1 generation.

c. Cross the F1 generation with itself and answer the following questions:

i. What is the probability of the following:

1. Heterozygous for Red, Homozygous for lots of vines, heterozygous for

ripe after picked?

2. Homozygous for yellow, heterozygous for lots of vines, homozygous

for ripe before picked.

ii. What is the probability of having a plant with yellow fruits, lots of vines and

ripening before picked?

iii. What is the probability of having a plant with red fruits, few vines and

ripening after picked?

Explanation / Answer

a. Let consider the gene R codes for red and "r" codes for yellow (red is dominant to yellow); lots of veins is coded by "V" and not a lot of wines coded by "v" (lots of vines are dominant to not a lot of vines), and ripe before picked "P" is coded by ripe after picked "p" (ripe before picked is recessive to ripe after picked).

(b). Cross between dpminant true breed (RRVVPP, Red, lots of veins, ripe before picked) and a recessive true breed (rrvvpp, yellow, not lots of veins, ripe after picked) will have the offspring with the following genotypes.

RRVVPP* rrvvpp = RrVvPp -----------> F1 (100% Red, lots of veins, ripe before picked).

The gametes produced by dominant parent are all RVP and the gametes produced by recessive parent are all rvp.

(c) cross between F1 (RrVvPp* RrVvPp) will have the offspring with the following genotypes. The possible gametes are, RVP, RVp, RvP, Rvp, rVP, rVp, rvP, rvp.

1. Heterozygous for Red, Homozygous for lots of vines, heterozygous for ripe after picked (RrVVPp)-------------------> 4/ 64 (6.25%)

2. Homozygous for yellow, heterozygous for lots of vines, homozygous for ripe before picked (rrVvpp) ----------------> 2/64 (3.13%).

(ii) The probability of having a plant with yellow fruits, lots of vines and ripening before picked (rrV_P_) -------------> 9/64

(iii) The probability of having a plant with red fruits, few vines and ripening after picked (R_vvpp) ----------------------> 3/64

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