Lecture 16 - Alleles And Inheritance

• Principle of Segregation - Principle of Independent Assortment

Alleles separate such that only one randomly chosen allele ends up in a gamete

-Separation of chromosomes (thus genes) is Independent (Separation of a pair of genes is independent of the separation of other pairs of genes) (The other allele a gamete receives (for a given gene) does not affect the allele received for other genes)

• chromosomes on a gamete are randomly selected from maternal and paternal chromosomes

Trait expressed the same way for homozygous and heterozygous genotypes • with a different expression for recessive traits

• neither allele masks the other • both expressed with heterozygous genotypes • characteristic intermediate to both homozygous genotypes

Roan coat color in shorthorn cattle

An allele is expressed in 2 dependent manner - offspring is intermediate between 2 alleles

• red + white = pink - palomino

Effect of one gene depends on the alleles present at one or more loci • modifier genes

Traits inherited through X chromosome

Trait is limited to a sex Milk production

Trait is influenced by gender • an allele that is dominant in one sex is recessive in the other sex (Polled vs horned for male vs female)

Identification and selection of superior animals To produce animals that excel for desired traits while minimizing occurrence of undesirable traits

Selection - obtain a desirable phenotype through choosing animals for mating Mating - pairing of males and females