Download Aquaculture Science

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
rr
r
r
R
Rr
Rr
R
Rr
Rr
RR
Punnett Square
• Developed by R.C. Punnett
• illustrates the possible combinations
for a particular trait
Rr
R
r
R
RR
Rr
r
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