9.1 mutations

what is a gene pool

a gene pools is the sum total of genes (genotypes, with all their variations, possessed by a particular species at a particular time (in a population)

what is allele frequency

how often each allele of gene occurs in the gene pool for that population.

what are factors that contribute to allele frequency and evolution

• Mutation

• Variation

• Natural selection

• Barriers to gene flow (isolation)

• Random genetic drift

• Migration and founder effect

• Speciation

• Genetic diseases

what is mutation

• A mutation is a permanent structural alteration in a organism's DNA.

• Mutations are the ultimate source of variation, introducing new alleles into a gene pool

• Mutations can have no effect, be favourable, or unfavourable for a population.

• Mutations in genes and chromosomes can result from errors in DNA replication, cell division or from damage caused by mutagens.

what are the two main types of mutations

• gene or point mutations

• chromosomal mutations

Gene or point mutation

• changes in the base sequence of a single gene so that the traits normally produced by that gene are changed or destroyed

  • These usually occur before cell division - during the replication of the DNA molecule.

chromosomal mutations

in which all or part of a chromosome is affected

what are mutagenic agents/mutagens

agents that increase the rate at which mutations occur.

what are examples of biological mutagens

bacteria, viruses

what are examples of chemical mutagens

• antibiotics

• mustard gas

• formaldehyde

• sulfur dioxide.

what are examples of physical mutagens

• radioactive wastes

• atomic and nuclear explosions

• x rays

• uv radiation

what are the ways in which mutagens can cause damage to DNA

• can trigger DNA replication errors

• can cause DNA breakage/lengthening

• can block DNA replication/damage DNA structure

• can chemically react and modify DNA

what is an induced mutation

genetic alterations that occur as a response to specific environmental conditions, often as a survival mechanism for cells under stress

what are spontaneous mutations

mutagens in biological processes, causing error such as in meiosis and mitosis.

what is a somatic mutation

• when the body cells, or somatic cells are involved with a mutation.

• Only the individual with the mutation is affected and does not pass on the mutation.

what are germinal or Germline mutations

• when reproductive cells are affected, and the mutation occurs in the gametes

• the mutations then may be passed on

• in this case, the individual is not usually affected but produces gametes with changed DNA.

what are the different effects of mutations

• missense mutation

• nonsense mutation

• neutral mutations

• silent mutations

what is a missense mutation

cause a change in the amino acid, and therefore in the protein produced.

non sense mutation

change the base sequence to the code to STOP. This means that the synthesis of the protein will stop, and so a shorter protein is produced that is unlikely to be able to fulfil it’s function

neutral mutations

cause a change in the amino acid; however the amino aid is of the same type and does not change the structure of the protein enough to change its function.

silent mutations

do not cause any change in the amino acid, and therefore in the protein produced. This is possible, as most amino acids are coded for by more than one base sequence.

what are the different ways point mutations can cause change in DNA.

can be due to a nucleotide being:

• inserted

• substituted

• deleted

inserted

a new nucleotide is added to the DNA strand

substituted

a existing nucleotide is replaced with a another one, with a different base.

deleted

a nucleotide is removed from the DNA strand

what is a frameshift

• a frameshift occurs when bases have been added or removed

• results in the series of three bases that code for an amino acid starting at a different base

• affect the outcome for all the DNA from that point on.

what are some chromosomal changes during a mutation

deletion - a piece of DNA is removed

duplication/insertion - a section of chromosome occurs twice

Inversion - breaks occur in a chromosome and the broken piece joins back in, but the way back around.

translocation - part of a chromosome breaks off and is rejoined to the wrong chromosome

non disjunction - during meiosis, chromosome pair does not separate and so one daughter cells has an extra chromosome and one has less.