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Alleles

Dominant - expressed when paired with a different allele Represented by an uppercase letter

Recessive - no effect when paired with a dominant allele Represented by a lowercase letter

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Alleles in an Individual

Homozygote - same two alleles (AA or aa)

Heterozygote - two different alleles (Aa) Genotype - the genetic makeup Phenotype - observable characteristics

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Genotype and Phenotype

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Genetic Cross

When two individuals are mated P generation - parent generation F1 generation - first generation

F2 generation - second generation

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Gene Mutations

Different alleles originally arose from a mutation

Mutation - change in DNA that makes up a gene

Mutations can be: Harmful Beneficial Neutral

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Basic Patterns of Inheritance

Mendel started with true breeding plants

Recessive trait skipped a generation

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Summarizing Mendel’s Theory

Alternative versions of genes (alleles) cause variation Offspring inherit one copy of a gene from each parent Alleles are dominant if they determine the phenotype Two copies of a gene separate in meiosis Gametes fuse randomly