The following pedigree shows the inheritance of a dominant...

The following pedigree shows the inheritance of a dominant trait. What is the chance that the offspring of the following matings will show the trait:
(a) $\mathrm{III}-1 \times \mathrm{III}-3 ;(\mathrm{b}) \mathrm{III}-2 \times \mathrm{III}-4 ?$

Key Concepts

Pedigree Analysis

Pedigree analysis is a method used in genetics to trace the inheritance patterns of traits through generations using family trees. It helps in determining the likely genotypes of individuals based on the observed phenotypes and relationships within the family, thereby identifying carriers and affected individuals.

Dominant Inheritance

Dominant inheritance refers to the pattern in which a trait or disorder is expressed when at least one copy of the dominant allele is present. Individuals with either one or two copies of the dominant allele will exhibit the trait, making it easier to determine when a dominant pattern is at play in pedigree studies.

Genotype Deduction

Genotype deduction involves inferring the genetic makeup (genotype) of individuals based on their phenotype and family history. This process is critical in understanding how traits are passed down, particularly when dominant or recessive alleles are involved, and is essential for predicting the probability of trait expression in offspring.

Punnett Square

A Punnett square is a diagram used to predict the genotypes of offspring from parental crosses. By organizing and combining the alleles from each parent, it visually represents all possible genetic outcomes and the associated probabilities, providing a straightforward method for understanding inheritance patterns.

Probability in Genetics

Probability in genetics involves using established ratios and calculations to determine the likelihood of an offspring inheriting a particular trait or genotype. This concept is applied after deducing the parents' genotypes, often using tools like the Punnett square, to quantify the chance of displaying the trait in future generations.

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