1. Human Variation & Evolution

Species - Definition

A group of individuals that can interbreed to produce fertile offspring

Allele

A different version of the same gene

Gene Pool

Sum of all alleles in a population

Population

A group of organisms of the same species living in the same place at the same time

Mutation

Permanent change in DNA sequence, due to mistakes when copied or environmental factors

Mutagen

Agents known to increase the rate of mutations

Allele Frequency

The study of the frequency of alleles in a gene pool for a particular popultion

What are the two types of mutations (by how much is affected)?

• Gene Mutations

• Chromosomal Mutations

Gene Mutations

Changes to a single gene during replication where traits are changed or destroyed

Chromosomal Mutations

All or part of a chromosome is affected

Mutagens - Examples

• Sulphur Dioxide

• Nuclear Explosions

• Some antibiotics

• X - Rays

• UV

• Cosmic Rays

• Mustard Gas

• Radioactive Waste

• Formaldehyde

Damage Caused by Mutagens

• Trigger DNA replication errors

• DNA breaks / lengthens

• Chemically react and modify DNA

What are the two causes of mutations?

• Induced

• Spontaneous

Induced Mutations

Induced mutations are mutations caused by mutagenic agents in the environment

Spontaneous Mutations

Spontaneous mutations are caused by random errors in biological processes such as meiosis and mitosis

What are the two types of mutations (based on the type of cells affected)?

Somatic Mutation

Germline Mutation

Somatic Mutation

• Occurs in body cells - mutation passed on to daughter cells during cells division

• Includes cancerous growth

Germline Mutation

Occurs in reproductive cells (gametes) - mutation passed onto embryo

Parent doesn’t have mutation

What are the types of mutation (based on the effect)?

• Missense Mutations

• Nonsense Mutations

• Neutral Mutations

• Silent Mutations

Missense Mutations

Cause a change in the amino acid, and therefore a protein is produced

Nonsense Mutations

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 its function

Neutral Mutations

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

Silent Mutations

Does 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.