Answer 1

Dr. Foster: ‘Excellent, you’ve chosen the correct answer regarding dominant and recessive alleles. Also remember: if two recessive alleles come together (aa), the recessive trait becomes visible in the phenotype. Last week, Professor York reminded us that the same phenotype can sometimes stem from different underlying genotypes. Now, let’s explore the difference between homozygote and heterozygote.’

You: ‘Yes, I recall there’s a specific way to describe individuals who have two of the same alleles versus those who carry different alleles.’

Dr. Foster: ‘Exactly. Understanding this helps us interpret data in our fruit fly crosses or any other genetic study. Take a look at these options. Which one accurately explains ‘homozygote’ and ‘heterozygote’?’

Description 1:
Homozygote for the gene is when the two alleles in an individual are the same (AA or aa).
Heterozygote for the gene is when the two alleles are different (Aa).

Description 2:
Heterozygote for the gene is when the two alleles in an individual are the same (AA or aa).
Homozygote for the gene is when the two alleles are different (Aa).

Description 3:
Heterozygote for the gene is when the two alleles in an individual are the same (AA or aa).
Homozygote for the gene is when the two alleles can be the same or different (Aa, AA, or aa).