Chapter 2- Animal Breeding And Genetics
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What is the genotype
Genetic makeup of an animal
What is the difference between animal breeding and animal propagation
• animal breeding is increasing the quality of each generation • animal propagation is increasing animal numbers
What is the phenotype
The animal’s actual performance
What influences the phenotype
Depends on the genetic makeup and the effects of temperature, feed, stress, and management
What are cells composed of
-outer membrane, inner cytoplasm, and nucleus
What does the nucleus contain
• heredity material of the cell - controls the cell’s growth, metabolism, and reproduction
Where is the genetic material found
Chromosomes
What determines the animal’s genotype and what are they
Genes are composed of DNA and each animal has a slightly different combination
What is necessary to determine a given trait and where are they located
A pair of genes is needed to determine a given trait and they are located on the same site on homologous chromosomes
What is a gene
Heredity unit consisting of a DNA sequence at a specific location on a chromosome
What is an allele
A gene found on the same location of homologous chromosomes
What is homozygous.
When both genes at a particular location on homologous chromosomes are on the same allele or are identical
What is heterozygous.
When two alleles are a given location in homologous chromosomes are not the same
What is dominant
A gene whose effect masks the phenotypic expression of its allele, shown by capital letters
What is recessive
A gene whose expression is hidden by a dominant gene and only expresses itself when in the homozygous state, shown by lower case letter
What qualitative traits have modifying genes that cause minor variations in phenotype
• coat color • honed versus pulled cattle • in cattle, at least nine major loci affect • hair color and hair pattern • in general, black is dominant
What is a mutation
When a trait that did not exist in either parent appears
What happens to mutations
• mutated genes are passed to the offspring - some mutations are beneficial, harmful, or little significance
What are common causes of mutations
• Exposure to various chemicals - exposure to radiation
What are the four systems mating
• inbreeding • line breeding • outcrossing • cross breeding
What is inbreeding.
Mating of animals that are more closely related to each other than the average relationship in a population
What does inbreeding cause
• A decrease in performance in traits such a fertility, survivability, and hybrid vigor called inbreeding depression • the undesirable genes tend to become more homozygous
How can inbreeding be useful
-With heavy culling it increases homozygosity for the superior genes
What happens with intensive inbreeding
D1- gets 50% of genes D2- gets 75% of genes D3- gets 87.5% of genes D4- gets 93.75% of genes