Sources of Genetic Variation

1. Sources of Genetic Variation

2. Sources of genetic variation • All organisms have variants of the same species – eg. We are all human, yet we don’t look the same.

3. 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.

4. 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.

5. 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.

6. 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?

7. 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!

8. 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.

9. 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.

10. 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

11. 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.

12. Chromosome mutations • Pieces of chromosome may be rearranged during meiosis.

13. 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.

14. 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.

15. More sources of genetic variation • Variation in a population can be continuous, or discontinuous.

16. 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.

17. 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.

18. 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.

19. Sources of Genetic variation – sexual reproduction • Sexual reproduction rearranges the genetic material into new combinations (that the offspring carry)

20. Independent Assortment • Genes are carried on chromosomes, 23 pairs in humans.

21. Independent Assortment • Genes are carried on chromosomes, 23 pairs in humans. • Each chromosome pair is sorted independently of the other pairs during meiosis.

22. 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)

23. Recombination • Alleles are often exchanged with a chromosome’s homologue (its ‘pair’ chromosome with the same genes) - recombination

24. 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.

25. 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.

26. Mate Selection • Variation is further enhanced by the choice of mate to produce offspring.

27. 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.