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Chapter 4: Patterns of Heredity. 4.1 Living things inherit traits in patterns 4.2 Patterns of heredity can be predicted 4.3 Meiosis is a special form of cell division. 4.2 Before you learned: Genes are passed from parents to offspring Offspring inherit genes in predictable patterns.
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Chapter 4: Patterns of Heredity 4.1 Living things inherit traits in patterns 4.2 Patterns of heredity can be predicted 4.3 Meiosis is a special form of cell division 4.2 Before you learned: Genes are passed from parents to offspring Offspring inherit genes in predictable patterns 4.2 Now, you will learn: How Punnett squares can be used to predict patterns of heredity How ratios and probability can be used to predict patterns of heredity
Punnett squares show possible outcomes of inheritance • Understanding patterns of heredity graphically: • Punnett Square: how the parents’ alleles might combine in offspring • Each parents has two alleles for a particular gene • An offspring receives one allele from each parent
Punnett Squares • The top of the Punnett square shows one parent’s alleles for this trait • Add two dominant regular alleles (DD) on top • Two recessive dwarf alleles (dd) on the side • Each potential offspring would have the same genotype: one dominant and one recessive allele (Dd) • The phenotype would show the dominant allele: regular height
Punnett Squares Recap Setting up and using a Punnett square is quite simple once you understand how it works. You begin by drawing a grid of perpendicular lines: Next, you put the genotype of one parent across the top and that of the other parent down the left side. For example, if parent pea plant genotypes were YY and GG respectively, the setup would be: In this example, 100% of the offspring will likely be heterozygous (YG). Since the Y (yellow) allele is dominant over the G (green) allele for pea plants, 100% of the YG offspring will have a yellow phenotype, as Mendel observed in his breeding experiments.
