Genetics and Punnett Squares

Front

What does homozygous mean?

Back

An organism is homozygous when it has two identical alleles for a particular gene (e.g., BB or bb).

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What does heterozygous mean?

Back

An organism is heterozygous when it has two different alleles for a particular gene (e.g., Aa).

Front

What is a dominant allele?

Back

A dominant allele is an allele that expresses its trait even when only one copy is present (e.g., A in Aa).

Front

What is a recessive allele?

Back

A recessive allele is an allele that only expresses its trait when two copies are present (e.g., tt).

Front

What are alleles?

Back

Alleles are different forms of a gene that can exist at a specific locus on a chromosome.

Front

What is a Punnett square?

Back

A Punnett square is a diagram used to predict the genotypes of offspring from a genetic cross.

Front

How do you determine the genotype from a Punnett square?

Back

The genotype is determined by the combination of alleles that appear in the squares of the Punnett square.

Front

What is the phenotypic ratio in a monohybrid cross?

Back

The phenotypic ratio in a monohybrid cross is typically 3:1 for dominant to recessive traits.

Front

What is the genotypic ratio in a monohybrid cross?

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The genotypic ratio in a monohybrid cross is typically 1:2:1 for homozygous dominant, heterozygous, and homozygous recessive genotypes.

Front

What is the significance of a test cross?

Back

A test cross is used to determine the genotype of an individual showing a dominant phenotype by crossing it with a homozygous recessive individual.