A woman expressing a dominant phenotype is heterozygous (Dd) for the gene.

What is the probability that two grandchildren of the woman who are first cousins to one another will each inherit the dominant allele?

Key Concepts

Dominant and Recessive Alleles

In genetics, alleles are different forms of a gene. A dominant allele, represented by a capital letter (e.g., D), masks the effect of a recessive allele (e.g., d) when both are present. Therefore, an individual with at least one dominant allele will express the dominant phenotype, while a recessive phenotype is only expressed when an individual has two recessive alleles.

Punnett Square

A Punnett square is a diagram used to predict the genetic outcomes of a cross between two individuals. By organizing the alleles of each parent, it allows for the visualization of possible allele combinations in offspring. This tool is essential for calculating probabilities of inheriting specific traits, such as dominant or recessive phenotypes.

Inheritance Patterns in Cousins

Cousins share a portion of their genetic material due to their common grandparents. When considering the inheritance of alleles, the probability that cousins inherit the same dominant allele depends on the genotypes of their parents. Understanding how alleles are passed down through generations is crucial for determining the likelihood of cousins sharing specific traits.