Genetic Inheritance Concepts

Phenotype

• The genetic makeup of an organism

• The physical trait expressed

• The evolutionary history of a species

• The behavior of an organism in its environment

At the end of meiosis, each gamete formed should only have 1 copy from each homologous chromosome pair

• Law of Segregation

• Law of Independent Assortment

• Law of Dominance

• Law of Genetic Variation

Overshadows the other allele in the heterozygous state

• Recessive

• Dominant

• Co-dominant

• Incomplete dominant

Recessive

• Only expressed in the homozygous state

• Expressed in both homozygous and heterozygous states

• Always expressed in the phenotype

• Dominant over other alleles

Incomplete Dominance

• When the genotype results in a phenotype where the two alleles are blended together.

• When one allele completely masks the effect of another allele.

• When both alleles are expressed equally in the phenotype.

• When a single allele is responsible for a trait.

Law of Dominance

• Some versions of genes are dominant over others

• All genes are equally expressed

• Dominant genes are always more common

• Recessive genes have no effect on traits

Polygenic Inheritance

• When several genes influence a trait

• When a single gene determines a trait

• When traits are inherited independently

• When environmental factors influence a trait

The actual alleles you inherit

• phenotype

• genotype

• karyotype

• allele frequency

Multiple Alleles

• More than two versions of a gene (more than just a 'dominant' and a 'recessive')

• Only two versions of a gene (dominant and recessive)

• A single version of a gene

• A gene that has no variations

Codominance

• When the heterozygous genotype results in a phenotype where both alleles are fully and separately expressed.

• When one allele completely masks the effect of another allele.

• When both alleles blend to form a new phenotype.

• When a single allele is expressed in the phenotype regardless of the other allele.