The process of adapting wild plants or animals to live in association with humans
Production requirements for animal domestication
Feeding and propernutrition
Animal health
Specific selection of stock
Domestication began
10,000 – 20,000 BCE
Selective breeding
Specific for improving growth, performance or any trait that is selected to improve genetic value and choose those who have the desired phenotype
Preventative medicine
Includes culling decisions and dealing with genetic diseases
Genetic diseases are usually untreatable, so it is usually best to cull the affected animal from breeding stock
Herd genetics
Can be determined through a variety of mating systems and selection methods and techniques
Purebred breeders
Most likely to seek genetic advice because their main products for sale are the genes
The majority of genetic progress is done by purebred breeders or seed stock suppliers
Genetic traits and diseases
Could be acquired in the following ways: Congenital, Familial, Inherited
Patterns of inheritance
Single gene
Chromosomal
Multifactorial
Teratogens are environmental or outside factors that influence the growth or traits of an individual and has nothing to do with the actual genetics
Family history
Very important when looking at genetics, including factors such as age of parents, number of offspring and their sex, miscarriages or stillbirths or their breed
Autosomal
Trait is passed on a gene that is NOT a sex chromosome
Autosomal dominant generalizations
Most are non enzyme protein disorders
Could have variable expressivity
Could have reduced or incomplete penetrance
Many are the result of a new mutation
Homozygote recessive is often lethal
Variable expressivity
The degree to which a phenotypic trait can be seen
Reduced penetrance
Either the presence or absence of a trait, where not all individuals with the allele express the phenotype
Many autosomal dominant traits are the results of new mutations within a species
Homozygous individuals for autosomal dominant traits usually results in early death
Dominance hierarchy
The ordered patterns of dominance
Melanocortin Receptor 1 gene (MC1R)
The gene that influences pigmentation
Melanocyte components
Nucleus
Mitochondrion
Rough ER
Golgi apparatus
Melanosomes
Phaeomelanin
Responsible for producing red, yellow and cream pigments
Eumelanin
Responsible for producing black, brown and gray pigments
Autosomal dominant inheritance
Could be by codominance or incomplete dominance, where heterozygotes have a different phenotype than either homozygote
Codominance
Merle colouring in Australian Shepherds
Incomplete dominance
Palomino colour in horses
Autosomal recessive generalizations
Most are enzyme deficiencies
Phenotypes are presented consistently
Symptoms are usually severe
Usually passed down through generations
Enzyme deficiencies
Arise from the inborn consequences of metabolism failure, often due to the build up of proteins that the lysosomes are unable to break down
If the phenotype is expressed by autosomal recessive inheritance, then the trait is usually consistent within families
Autosomal recessive diseases are usually severe, present at birth, and lethal if left untreated
Consanguinity
The state where traits are passed on and present throughout generations due to inbreeding
The implication of autosomal recessive inheritance is to cull the affected individuals, as both parents are 'obligate' carriers with a 0% chance of unaffected offspring
Carrier detection tests
Typically performed on parents who are carriers to see what the chances of affected offspring are
Breeding tests
Involve mating a sire to an affected or heterozygous dam to see if affected offspring are born, to determine if the sire is a carrier
Direct tests
Could be biochemical (testing proteins and enzymes) or DNA (PCR tests looking for mutations)
Indirect tests
DNA linkage tests used when the causative gene is not known, to find a marker linked to the suspected gene
Sex linked inheritance
Occurs when the gene is on the sex chromosome, with fewer genes
Xinactivation
Occurs in female mammals, where one of the X chromosomes is inactivated
X linked diseases
Muscular dystrophy in dogs, hemophilia in horses and dogs