AnSci Final Review

• Animal domestication


  The process of adapting wild plants or animals to live in association with humans
• Production requirements for animal domestication

  • Feeding and proper nutrition
  • 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, since genetic diseases are usually untreatable, 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
• Ways genetic traits and diseases could be acquired

  • Congenital (present at birth)
  • Familial (inherited but environment also contributes)
  • Inherited (passed on from parent to offspring)

  
• Single gene inheritance


  Occurs when only a single gene gets coded for a trait
• Chromosomal inheritance


  The trait is being passed on through the replication of chromosomes, this type has more impact since there could be a lot of damaged DNA
• Multifactorial inheritance


  Includes many things such as genes, chromosomes and environment
• Teratogens


  Environmental or outside factors that influence the growth or traits of an individual and has nothing to do with the actual genetics
• Family history


  • Factors such as age of parents, number of offspring and their sex, miscarriages or stillbirths or their breed
• Autosomal dominant inheritance


  A gene that is NOT a sex chromosome is passed on and the dominant trait is expressed
• Autosomal dominant generalizations


  • Most are non enzyme protein disorders
  • Could have variable expressivity (hard to see but means to what degree a specific trait is noticeable)
  • Could have reduced or incomplete penetrance (trait would either fully be present or absent)
  • 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, if reduced then not all individuals show the trait
• 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


  Dominance patterns can be ordered
• Melanocortin Receptor 1 gene (MC1R)


  The gene that influences pigmentation
• Melanocytes


  • Found at the base of the hair follicle and has dark and light pigments, organelles include the nucleus, mitochondrion, rough ER, Golgi apparatus and melanosomes
• Phaeomelanin


  Responsible for producing red, yellow and cream pigments
• Eumelanin


  Responsible for producing black, brown and gray pigments
• Autosomal dominant inheritance by codominance

  Heterozygote could have a different phenotype than either homozygote, both phenotypes are expressed together but observed separately
• Autosomal dominant inheritance by incomplete dominance


  Both phenotypes are expressed as a blended appearance

  
• 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 is passed down through generations or it is clear that the trait is passed down from ancestors
• Enzyme deficiencies


  Arise from the inborn consequences of metabolism failure, could be the product of the build up of proteins because the lysosomes are unable to break them 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


  States that traits are passed on and present throughout generations
• Implications of autosomal recessive inheritance

  Culling the individuals is usually the best course of action, since both parents are "obligate" carriers and there is a 0% chance the offspring will be unaffected
• Carrier detection tests


  Typically performed on parents who are carriers to see what the chances of the affected offspring are
• Breeding tests


  Involve the mating of a sire to an either affected or heterozygous dam to see if the affected offspring are born, if the offspring is affected then the sire is a carrier
• Direct tests


  Could be biochemical (testing of proteins and enzymes) or DNA tests (PCR tests to look for mutations in the sequence)
• Indirect tests


  DNA linkage tests used when the causative gene is not known, only the location or biochemical tests of the gene are known
• Carrier detection tests for dominant disorders


  Used if the dominant disorder is late onset so that you are aware of the genotype prior to breeding
• Sex linked inheritance


  Occurs when the gene on the sex chromosome has fewer genes