In goats, the development of the beard is due to a recessive gene. The following cross involving true-breeding goats was made and carried to the F₂ generation: Offer an explanation for the inheritance and expression of this trait, diagramming the cross. Propose one or more crosses to test your hypothesis.

Key Concepts

Recessive and Dominant Genes

In genetics, traits are often determined by alleles, which can be dominant or recessive. A dominant allele masks the effect of a recessive allele when both are present. In this case, the beard trait in goats is controlled by a recessive gene, meaning that a goat must inherit two copies of this recessive allele to express the beard phenotype.

Punnett Square

A Punnett square is a diagram used to predict the genetic outcomes of a cross between two organisms. It allows for the visualization of how alleles from each parent combine in their offspring. By setting up a Punnett square for the true-breeding goats, one can determine the expected genotypic and phenotypic ratios in the F₂ generation, aiding in understanding the inheritance pattern of the beard trait.

Test Cross

A test cross is a breeding experiment used to determine the genotype of an individual exhibiting a dominant phenotype. By crossing this individual with a homozygous recessive individual, one can observe the offspring's phenotypes to infer the unknown genotype. This method is useful for confirming hypotheses about the inheritance of traits, such as the beard trait in goats.