Genetics
- Created by: StephanieWatson
- Created on: 07-12-13 13:09
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- Genetics
- Study of the science of heredity
- Gregor Mendel 1800's
- Mendel's 1st law - genes are passed on. Offspring - First Filial Generation
- Mendel's 2nd law - if members of 1st filial generation are crossed with another then the resultant offspring will be in a 3:1 ratio dominant to recessive
- Gregor Mendel 1800's
- Chromosomes
- DNA molecules
- 2 Identical Chromatids
- Mammals - arranged in pairs. One from Mother and one from father
- Genes
- Site of gene on a chromosome = Locus
- Code for a particular protein
- Alleles / Allelomorphs
- Different versions of a given gene
- Dominant - suppress the effect of others
- Reccessive -Alleles masked by the dominant version
- Genotype
- Heterozygous - 2 different alleles
- Homozygous - two identical versions of a gene
- Phenotype
- Physical appearance
- Back Crossing to the recessive
- Homozygous animals will always breed true for a particular trait
- Test the genotype
- Reality - look back at stud books
- Heterozygous X Homozygous. Progressive Retinal Atrophy inherited this way carried on Simple Autosome recessive gene - Dogs
- Sex Linked genes
- Y is little, so most sex linked characteristics found on X chromosome
- Females tend to be carriers, Males tend to show condition
- Tortoiseshell cats - orange colouration carried on X chromosome -> has to have 2 X chromosomes -> tend to be female
- Can be male, not hermaphodite, must be chromosomally slightly abnormal - XXY or XXXY
- Y is little, so most sex linked characteristics found on X chromosome
- Epistasis
- Where a different gene altogether influences the expession of the alleles
- Mutation
- Rare occasions mistakes are made by the body whilst copying the DNA in gamete formation
- Lethal Mutations - resultant gametes so altered that are inconsistent with life, individual cannot survive
- Some may not affect the new individual at all. Others convey an advantage - Evolutionary change
- Rare occasions mistakes are made by the body whilst copying the DNA in gamete formation
- Inbreeding
- Involves mating of individuals who are more closely related than animals chosen from general population
- More likely to have many genes in common, increases likelihood of producing offspring with recessive traits
- Less desirable traits may be passed along too.
- Pedigree dogs - increased incidence of disease
- Line Breeding
- Form of inbreeding
- Involves animals that are not so closely related
- Mating within a certain family or line
- Increases likelihood of obtaining desirable characteristics, without too high a risk of producing undesirable ones
- Out-breeding
- Breeding of individuals less closely related than mates chosen at random in the population
- Increases heterozygousity and introduces new genes into the population
- Heterosis/Hybrid vigour - this cross conveys this, conveys some superiority on the heterozygote
- Deformities/Malformations
- Deviation from normal anatomy
- Foetal development or acquired during life
- Congenital Abnormalities
- Abnormality present from birth
- May be inherited from parents through the genes or may be due to environmental factors which may result in failure of normal foetal development e.g. radiation or viral infections
- Teratogen - Agent that induces a birth defect
- Hereditary defects
- Caused by genes inherited from parents
- May not be apparent at birth - PRA
- Study of the science of heredity
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