Inheritance based on gene interactions

They hypothesized the chemical nature of function of gene

J. Watson and F. Crick on 1956

Is a segment of DNA

Gene

involves separation of alleles at a locus during meiosis.

Segregation

shows the ratio of different types of offspring.

Segregation Ration

Specific phenotypes are often controlled by one or more gene pairs whose alleles exhibit modes of expression other than dominance and recessiveness.

Gene interaction

Genes express themselves phenotypically in two ways:

Non-additive gene interaction and Additive gene action

expression of one gene doesn’t necessarily add to the phenotypic expression of the other

members of allelic pairs may interact to produce a certain phenotypic effect

two entirely separate pairs of genes may interact with each other to produce a particular phenotype

Non-additive gene interaction

the effect of one gene contributes to the effect of another gene that contributes to the same phenotype

Additive Gene action

When two genes affecting a character in different manners occur together in an individual and occupy identical locations in the homologous chromosomes, the individual is said to be ____________

heterozygous

contains one gene for polled trait, one gene for horned trait

Heterozygous genotype

Distinct, detectable genetic expression of two alleles.

Codominance

This occurs if 2 alleles are responsible for the production of 2 distinct, detectable gene products.

Codominance

Resulting heterozygous individuals are superior to either homozygotes.

Heterosis or hybrid vigor

They affect traits related to physical fitness or vigor

Hybrid vigor or heterosis

Epistasis, came from the greek word ________

Stoppage

It occurs when the expression of one gene or gene pair masks or influences the expression of another gene or gene pair.

Epistasis

Epistasis may occur under different conditions:

Homozygous presence of a recessive allele may prevent or override the expression of other alleles at a second locus.

A single dominant allele at first locus may influence expression of alleles at second gene locus.

Two gene pairs may complement one another such that at least one dominant allele at each locus is required to express a particular phenotype.

The previous patterns of inheritance involves simple autosomal inheritance. However, not all loci are found on the autosomes but also on the sex chromosomes. This pattern of inheritance is said to be ______________

sex-linked.

refer to traits determined by the genes that are linked on the X-chromosome.

Sex-linked

are of prime importance on selection programs. This is because the main aim when deciding which animals to breed is to choose those that are going to have the best offspring

Breeding Values

refer to the portion of the phenotypic variance in a population that is due to heredity. It includes mostly additive types of gene action.

Heritability Estimates