Heredity and Punnett Squares

Front

What are alleles?

Back

Different forms of a gene.

Front

What does it mean if an allele is dominant?

Back

It means that the trait it represents will be expressed in the phenotype even if only one copy is present.

Front

What is the genotype for a homozygous dominant organism?

Back

The genotype is represented by two uppercase letters, e.g., 'AA'.

Front

What is the genotype for a homozygous recessive organism?

Back

The genotype is represented by two lowercase letters, e.g., 'aa'.

Front

What is a heterozygous genotype?

Back

A genotype consisting of one dominant and one recessive allele, e.g., 'Aa'.

Front

In a Punnett square, what do the letters represent?

Back

The letters represent the alleles from each parent.

Front

What is the purpose of a Punnett square?

Back

To predict the probability of offspring genotypes and phenotypes from parental genotypes.

Front

If a tall pea plant (T) is crossed with a short pea plant (t), what are the possible genotypes of the offspring?

Back

The possible genotypes are Tt (tall) and tt (short).

Front

What is the probability of getting a homozygous recessive offspring from a cross between Tt and tt?

Back

The probability is 50%.

Front

What does it mean for a trait to be recessive?

Back

A recessive trait is only expressed in the phenotype if two copies of the recessive allele are present.