Question 1. (5 Marks)

Pea pod shape is controlled by a one gene - two allele genetic system. Full pod shape is completely

dominant to constricted pea pod shape. Pea plant size is also controlled by a one gene – two allele

system with tall size being completely dominant to dwarf size. Given a plant was heterozygous for pod

shape and homozygous recessive for plant size:

a What is the phenotype of this plant?

b.If this plant was crossed to a dihybrid (heterozygote), what would be the phenotypic ratio of pod

shape among the progeny?

c.What would be the phenotypic ratio of plant size? 

d. What would be the phenotypic ratio of pod shape and plant size together? 

Question 2. (10 Marks)

A pure breeding, tall pea plant white flowers is crossed with a pure-breeding short plant with red flowers.

The F1 plants are tall with red flowers. When allowed to self-fertilise themselves, these F1 plants

produce the following F2: 326 tall, red; 104 tall, white; 117 short red and 29 short white. Explain these

data; indicating genotypes of the parents and the different F2 phenotypes. What is the expected

numbers in the various F2 classes? Test the goodness of fit between the data and your hypothesis

using .

Question 3. (5 Marks)

In any breeding program (i.e. for cattle, horses, dogs guinea pigs), which is more easily eliminated from

a population; a trait expressed by a completely dominant allele, or a trait expressed by a completely

recessive allele? 

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