Explaining inheritance: Mendel and beyond | Starter Quiz | Oak National Academy

One gene controls pea pod shape. The inflated pod allele (I) is dominant. The constricted pod allele (i) is recessive. How many i alleles must a pea plant inherit to have constricted pods?

• 1

• 1 or 2

• 2

Answer explanation

A plant must inherit two recessive alleles to have constricted pea pods, because the characteristic associated with a recessive allele is only shown when the genotype is homozygous.

The diagram is a model of the inheritance of I and i alleles from two parent pea plants. What is this type of diagram called?

• evolutionary tree

• family tree

• food web

• Punnett square

Answer explanation

The Punnett square diagram is a model of the inheritance of alleles of a single gene.

Two pea plants with the genotype Ii are bred together. Which Punnett square has been completed correctly to show the possible genotypes of the offspring plants?

• 
• 
• 
• 

Answer explanation

Punnett square C correctly shows that each offspring plant inherits one allele from each of its parents.

The Punnett square shows that the proportion of offspring that will have the genotype ii is ___ in 4.

Answer explanation

Only one of the four possible genotypes in the offspring is ii.

What is the probability that an offspring of these parent plants will have the genotype ii?

Answer explanation

Only one of the four possible genotypes in the offspring is ii, so the probability is 1 ÷ 4 = 0.25.

The allele for inflated pods (I) is dominant. The Punnett square shows that the ratio of individuals with inflated pods to constricted pods in the offspring will be ___:1.

Answer explanation

The allele for inflated pods (I) is dominant, so offspring with the genotype II or Ii will have inflated pods. Only offspring with the genotype ii will have constricted pods.