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. 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 AAATCGTTTTCGMutant 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.