Introduction to Punnett Squares Quiz

What is a Punnett square used for in genetics?

• To calculate the probability of genetic disorders

• To predict the possible genotypes of offspring

• To determine the age of fossils

• To measure the growth rate of plants

Answer explanation

A Punnett square is a tool used in genetics to predict the possible genotypes of offspring based on the genetic makeup of the parents, making it essential for understanding inheritance patterns.

Which of the following terms describes an organism with two identical alleles for a trait?

• Heterozygous

• Homozygous

• Dominant

• Recessive

Answer explanation

An organism with two identical alleles for a trait is called homozygous. In contrast, heterozygous refers to having two different alleles. Dominant and recessive describe the expression of traits, not the allele configuration.

In a monohybrid cross between two heterozygous parents (Aa x Aa), what is the probability of obtaining a homozygous recessive offspring?

• 0%

• 25%

• 50%

• 75%

Answer explanation

In a monohybrid cross (Aa x Aa), the offspring genotypes are 25% AA, 50% Aa, and 25% aa. The homozygous recessive genotype (aa) occurs in 25% of the cases, making the probability of obtaining a homozygous recessive offspring 25%.

If a Punnett square shows a cross between a homozygous dominant parent (AA) and a homozygous recessive parent (aa), what will be the genotype of all the offspring?

• AA

• Aa

• aa

• A mix of AA, Aa, and aa

Answer explanation

In a Punnett square cross between AA (homozygous dominant) and aa (homozygous recessive), all offspring will inherit one dominant allele (A) and one recessive allele (a), resulting in the genotype Aa for all offspring.

Which of the following represents a genotype?

• Blue eyes

• Aa

• Tall

• Round seeds

Answer explanation

A genotype refers to the genetic makeup of an organism, represented by alleles. 'Aa' is a genotype indicating one dominant and one recessive allele, while the other options describe phenotypes or traits.