Alleles Phenotype and Hetero vs. Homozygous

prerequisite review

What is a gene?

• A segment of DNA that codes for a type of protein

• It determines the characteristics that we develop (single or multiple).

What are alleles?

• Different versions of the same gene

• You inherit one from each parent

What is homozygous?

When both alleles are the same (e.g., AA or aa).

What is heterozygous?

When the two alleles are different (e.g., Aa).

What is a dominant allele?

An allele that is expressed if present (e.g., in Aa or AA genotypes).

What is a recessive allele?

An allele that is suppressed unless both copies are present (e.g., only expressed in aa, not in Aa)

What is a genotype?

• The collection of alleles for a particular gene (e.g., Aa vs. AA).

What is a phenotype?

The characteristics you get from the genotype (the observable traits resulting from allele expression).

How do phenotypes compare in Aa vs. AA?

The phenotypes are the same because both express the dominant trait, regardless of the genotype (heterozygous or homozygous).

How do genotypes compare in Aa vs. AA?

Even if phenotypes are the same— one might be heterozygous (Aa) and the other homozygous (AA).

Summarize the relationship between genotype and phenotype.

• Genotype is the alleles you have (e.g., Aa or AA)

• Phenotype is the expression of those alleles (e.g., dominant trait in both Aa and AA).