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Sources of Genetic Variation. Sources of genetic variation. All organisms have variants of the same species – eg . We are all human, yet we don’t look the same. Sources of genetic variation. All organisms have variants of the same species – eg . We are all human, yet we don’t look the same.
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Sources of genetic variation • All organisms have variants of the same species – eg. We are all human, yet we don’t look the same.
Sources of genetic variation • All organisms have variants of the same species – eg. We are all human, yet we don’t look the same. • Genetic variation is mostly to do with the ‘shuffling’ of the existing genetic material into new combinations.
Sources of genetic variation • All organisms have variants of the same species – eg. We are all human, yet we don’t look the same. • Genetic variation is mostly to do with the ‘shuffling’ of the existing genetic material into new combinations. • These new combinations get passed on from generation to generation.
Sources of genetic variation • All organisms have variants of the same species – eg. We are all human, yet we don’t look the same. • Genetic variation is mostly to do with the ‘shuffling’ of the existing genetic material into new combinations. • These new combinations get passed on from generation to generation. • In addition to this, mutation creates new alleles in individuals and is an important part of the evolutionary process.
Sources of genetic variation • All organisms have variants of the same species – eg. We are all human, yet we don’t look the same. • Genetic variation is mostly to do with the ‘shuffling’ of the existing genetic material into new combinations. • These new combinations get passed on from generation to generation. • In addition to this, mutation creates new alleles in individuals and is an important part of the evolutionary process. • Why?
Gene Mutations • Mutations may cause alterations in the genetic instructions coded in the DNA of chromosomes. Original DNA AAATCGTTTTCG Mutant DNA AAATCTTTTTCG Substitute T instead of G causes a whole new amino acid to be made – in turn making a different protein, etc etc. Basically stuffs everything up!
Gene Mutations • Mutations may cause alterations in the genetic instructions coded in the DNA of chromosomes. • Most mutations are harmful, some are neutral, while very few may provide some improvement on the earlier version of the gene.
Gene Mutations • Mutations may cause alterations in the genetic instructions coded in the DNA of chromosomes. • Most mutations are harmful, some are neutral, while very few may provide some improvement on the earlier version of the gene. • Mutations may be accumulated (inherited) over many generations.
Gene Mutations • Mutations may cause alterations in the genetic instructions coded in the DNA of chromosomes. • Most mutations are harmful, some are neutral, while very few may provide some improvement on the earlier version of the gene. • Mutations may be accumulated (inherited) over many generations. • http://www.youtube.com/watch?v=kp0esidDr-c
Gene Mutations • Mutations may cause alterations in the genetic instructions coded in the DNA of chromosomes. • Most mutations are harmful, some are neutral, while very few may provide some improvement on the earlier version of the gene. • Mutations may be accumulated (inherited) over many generations. • http://www.youtube.com/watch?v=kp0esidDr-c • So, in general, a mutation is a change in some part of the DNA which is random, and alters the whole course of that section of DNA.
Chromosome mutations • Pieces of chromosome may be rearranged during meiosis.
Chromosome mutations • Pieces of chromosome may be rearranged during meiosis. • Sections can be duplicated, turned upside down, moved from one chromosome to another, or lost.
Chromosome mutations • Pieces of chromosome may be rearranged during meiosis. • Sections can be duplicated, turned upside down, moved from one chromosome to another, or lost. • Most cases are harmful, but occasionally they can be helpful.
More sources of genetic variation • Variation in a population can be continuous, or discontinuous.
More sources of genetic variation • Variation in a population can be continuous, or discontinuous. • Discontinuous = determined by a single gene. EG – you either have the trait, or you don’t. Blood groups are a good example because you are one or another – you can’t be in between.
More sources of genetic variation • Variation in a population can be continuous, or discontinuous. • Discontinuous = determined by a single gene. EG – you either have the trait, or you don’t. Blood groups are a good example because you are one or another – you can’t be in between. • Continuous = traits determined by a large number of genes. EG – Height. Everyone ranges.
More sources of genetic variation • Variation in a population can be continuous, or discontinuous. • Discontinuous = determined by a single gene. EG – you either have the trait, or you don’t. Blood groups are a good example because you are one or another – you can’t be in between. • Continuous = traits determined by a large number of genes. EG – Height. Everyone ranges. • Environmental influences (eg. different diets) also contribute to an observable variation in a population – it may help or hinder their true genotype.
Sources of Genetic variation – sexual reproduction • Sexual reproduction rearranges the genetic material into new combinations (that the offspring carry)
Independent Assortment • Genes are carried on chromosomes, 23 pairs in humans.
Independent Assortment • Genes are carried on chromosomes, 23 pairs in humans. • Each chromosome pair is sorted independently of the other pairs during meiosis.
Independent Assortment • Genes are carried on chromosomes, 23 pairs in humans. • Each chromosome pair is sorted independently of the other pairs during meiosis. • This random shuffling makes a huge variety of gametes from a single individual (parent)
Recombination • Alleles are often exchanged with a chromosome’s homologue (its ‘pair’ chromosome with the same genes) - recombination
Recombination • Alleles are often exchanged with a chromosome’s homologue (its ‘pair’ chromosome with the same genes) – recombination • This is usually a result of ‘crossing over’ – the mutual exchange of pieces of chromosome which swap the groups of genes.
Recombination • Alleles are often exchanged with a chromosome’s homologue (its ‘pair’ chromosome with the same genes) – recombination • This is usually a result of ‘crossing over’ – the mutual exchange of pieces of chromosome which swap the groups of genes. • Errors in crossing over can result in chromosome mutations.
Mate Selection • Variation is further enhanced by the choice of mate to produce offspring.
Mate Selection • Variation is further enhanced by the choice of mate to produce offspring. • “Choosiness” will provide different combinations of genes that will come together in the offspring, depending on which two parents mate.