Patterns of Inheritance: Terminology

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Patterns of Inheritance Terminology
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Some Important Terms

• Genetics study of heredity
• Heredity the passing of traits from parents to
  their offspring

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Traits Are Determined by Genes

• Trait variation of a particular inherited
  character
• Gene unit of inherited information in DNA
• Typically, traits are determined by genes.

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Genotype vs. Phenotype

• Genotype the genetic makeup of an organism
• Phenotype the observable traits of an organism
• Typically, the phenotype is determined by the
  genotype.

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Variation Among Genotypes

• Populations of organisms frequently have several
  different versions of the same gene. These
  versions are called alleles.
• Allele alternative form of a gene

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Combinations of Alleles

• As we have already seen, diploid organisms have
  two copies (alleles) of the same gene (homologous
  chromosomes)
• Homozygous having identical alleles for a gene
• Heterozygous having different alleles for a gene

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Dominance

• the biological principle that recognizes that
  some alleles are dominant and some are recessive

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Dominant vs. Recessive

• Dominant descriptive of an allele in a
  heterozygous individual that appears to be the
  only one affecting a trait
• Example both homozygous dominant (AA) and
  heterozygous (Aa) individuals exhibit the
  dominant trait
• Recessive descriptive of an allele in a
  heterozygous individual that does not appear to
  affect a trait
• Example only homozygous recessive (aa)
  individuals exhibit the recessive trait

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Example of a Recessive TraitFainting Goats
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