The Science of Animal Agriculture Ch. 4 The Science of Genetics.
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Transcript of The Science of Animal Agriculture Ch. 4 The Science of Genetics.
The Science of Animal Agriculture
Ch. 4
The Science of Genetics
Genetic Basics
• Gregor Mendel (1822-1884)– first person to develop workable theory
• transfer of traits
– used garden peas
– based on purebred strains
Law of Dominance
• overriding or dominant factors make certain recessive traits disappear
Law of Segregation
• the alleles responsible for the traits from each parent are separated and then combined with factors from the other parent at fertilization
Law of Independent Assortment
• Factors for certain characteristics are passed from parents to the next generation separate from the other factors or genes that transmit other traits
Punnett Square
• Developed by R.C. Punnett
• illustrates the possible combinations for a particular trait
RRR
R
rrrr
Rr
Rr
Rr
Rr
Punnett Square
• Developed by R.C. Punnett
• illustrates the possible combinations for a particular trait
RrR
r
RrrR
RR
Rr
Rr
rr
Genetics Basics
• genes are in chromosomes– different animals have different chromosome
#’s• cattle = 30 pairs• horses = 32 pairs• apples = 34 pairs
• each allele contains two genes– one by each parent
Selective Breeding
• the choosing of individuals of a single strain and species
• artificial selection
• need to avoid inbreeding
Hybridization
• the crossing of different species
• hybrid vigor– the ability of hybrids or strain crosses to
exceed the parents in performance
• most hybrids are sterile
Crossbreeding
• the mating of unrelated strains of the same species to avoid inbreeding