Question 5 – Patterns of inheritance - Questions

Bulb color in onions (Allium cepa) is determined by two genes, $I/i\,$ and $R / r$ .

$I\,$ is a dominant allele that inhibits pigment production, resulting in white onion bulbs.
The recessive allele, $i$ , allows pigment production.
$R\,$ is a dominant allele that codes for the production of a red pigment.
Onion plants that are homozygous for the recessive allele, $r$ , produce yellow bulbs (in the absence of dominant inhibiting alleles).

A true-breeding white onion plant was cross-pollinated with a true-breeding yellow onion plant. All $F_1\,$ offspring had the genotype $I i R r$ .

Identify the following:

State the type of gene interaction shown by the genes $I/i\,$ and $R / r$ .

Suggest how the dominant allele $I\,$ inhibits the expression of allele $R$ .

Bulb color in onions (Allium cepa) is determined by two genes, $I/i\,$ and $R / r$ .

$I\,$ is a dominant allele that inhibits pigment production, resulting in white onion bulbs.
The recessive allele, $i$ , allows pigment production.
$R\,$ is a dominant allele that codes for the production of a red pigment.
Onion plants that are homozygous for the recessive allele, $r$ , produce yellow bulbs (in the absence of dominant inhibiting alleles).

A true-breeding white onion plant was cross-pollinated with a true-breeding yellow onion plant. All $F_1\,$ offspring had the genotype $I i R r$ .

Identify the following:

State the type of gene interaction shown by the genes $I/i\,$ and $R / r$ .

Suggest how the dominant allele $I\,$ inhibits the expression of allele $R$ .

Patterns of inheritance