Understanding Genetics and Punnett Squares

What is a dominant trait?

• A trait that is masked by another trait

• A trait that is expressed when at least one allele is present

• A trait that is only expressed when two identical alleles are present

• A trait that is less common in a population

What is a recessive trait?

• A trait that is always expressed

• A trait that is expressed only when two identical alleles are present

• A trait that is more common in a population

• A trait that can mask other traits

In a Punnett Square, what do the letters inside the boxes represent?

• The possible genotypes of the offspring

• The phenotypes of the parents

• The number of offspring

• The dominant traits only

If a homozygous dominant parent (AA) is crossed with a homozygous recessive parent (aa), what is the genotype of the offspring?

• AA

• Aa

• aa

• Aa and aa

What is the probability of obtaining a homozygous recessive offspring (aa) from a heterozygous (Aa) and homozygous recessive (aa) cross?

• 0%

• 25%

• 50%

• 100%

In a monohybrid cross between two heterozygous parents (Aa x Aa), what is the phenotypic ratio of the offspring?

• 1:1

• 3:1

• 1:2:1

• 2:2

What does a Punnett Square help predict?

• The exact number of offspring

• The possible genotypes and phenotypes of offspring

• The lifespan of offspring

• The environmental impact on traits

If a Punnett Square shows a 1:2:1 genotypic ratio, what are the possible genotypes?

• AA, Aa, aa

• Aa, Aa, Aa

• AA, AA, aa

• Aa, aa, aa

In a cross between a homozygous dominant (BB) and a heterozygous (Bb) individual, what is the probability of obtaining a homozygous dominant (BB) offspring?

• 25%

• 50%

• 75%

• 100%

What is the phenotypic ratio of a cross between two heterozygous individuals (Bb x Bb) for a trait where B is dominant?

• 1:1

• 3:1

• 1:2:1

• 2:2