Variation

- Genetic variation: Controlled by genes; can't be changed.
- Environmental variation: Controlled by the environment, e.g., sun, piercings, and hair dye.
- Genes and environment, such as skin colour and height, can cause variation.

- Continuous variation: (Quantitative data), range of values (e.g., height). The information is displayed on a line graph.
- Discontinuous variation: (Discrete data), categories you fall into, e.g., blood group. The information is displayed on a bar chart.

Genetic Variation Causes:

1) Meiosis: Genetically different gametes.
2) Sexual reproduction: A random choice of partners.
3) Mutations

- A mutation is a change to the base sequence of a gene.
- They can be random and spontaneous, occurring during DNA replication before a cell divides, or caused by mutagens—chemicals, like tar in cigarettes. e.g., X-rays

Types of Mutation:

- Insertion

- Mutations create new alleles.
→ Because a mutation changes the base sequence of DNA, it affects protein structure—it won't fit into the enzyme's active site anymore.
- It codes for a different sequence of amino acids.
- The protein will be a different shape and may not work properly.
→ For instance, cystic fibrosis results in a mutation in the CFTR gene.

- If a mutation happens in a body cell, it might cause cancer.
- If a mutation occurs in a cell that produces sperm or egg cells, it may cause a genetic disorder in the offspring.

- Sometimes, a mutation can be beneficial.
- Some mutations are neutral—neither good nor bad.
- Sickle cell anaemia is a recessive condition that can be beneficial in countries where malaria is prevalent.

- Mutations can sometimes occur in non-coding DNA.
→ These are sections of DNA that don't code for proteins.
→ 98.5% of our DNA is non-coding.
- Some of these sections of DNA have no known function, but some sections are involved in gene regulation—switching genes on and off.
- If a mutation happens in a region like this, then a gene may be incorrectly switched on/off, and mRNA and proteins are made in that cell. This leads to incorrect transcription and alteration of the gene.
→ If the gene hasn't changed but how it is expressed has changed.

- The greater the genetic variation, the more likely a species is to survive any environmental changes.