Understanding Genetic Crosses: A Step-by-Step Guide

This page provides a detailed explanation of how to solve genetic inheritance problems using Punnett squares. The content focuses on calculating the probability of a child being born without freckles to parents who both have freckles and are heterozygous.

Definition: A Punnett square is a diagram used to predict the possible genotypes of offspring based on the genotypes of their parents.

Example: The problem demonstrates inheritance of freckles where:

• A = dominant allele (freckles present)
• a = recessive allele (no freckles)
• Parents' genotype: Aa (heterozygous)

Vocabulary:

• Heterozygous: Having two different alleles for a particular gene
• Allele: Alternative forms of a gene
• Genotype: Genetic makeup of an organism

Highlight: The solution shows that when both parents are heterozygous (Aa), there is a 25% chance of having a child without freckles (aa).

Quote: "Prawdopodobieństwo urodzenia się dziecka, u którego ujawni się cecha recesywna wynosi 25%"

The page methodically explains the process of setting up and completing a Punnett square, starting with labeling parent genotypes, identifying possible gametes, and determining offspring genotypes. The final calculation demonstrates that one out of four possible combinations (25%) results in a child without freckles.