There are over 4,000 identified single gene defects that lead to genetic disease, but most are very rare
Recessive conditions tend to be more common, as the faulty allele can be present in carriers without causing disease. Dominant conditions may often have a late onset, as this does not prevent reproduction and the transfer of the faulty allele
- Any allele that adversely affects survival and hence the capacity to reproduce is unlikely to be passed on to offspring
Recessive conditions tend to be more common, as the faulty allele can be present in carriers without causing disease. Dominant conditions may often have a late onset, as this does not prevent reproduction and the transfer of the faulty allele
3.4 mutations & genetic disease
Understanding:
3.4.U10 - Radiation and mutagenic chemicals increase the mutation rate and can cause genetic diseases and cancer
3.4.U10 - Radiation and mutagenic chemicals increase the mutation rate and can cause genetic diseases and cancer
Objectives:
- State two factors that can increase the mutation rate.
- Outline the effects of gene mutations in body cells and gamete cells
A gene mutation is a change to the base sequence of a gene that can affect the structure and function of the protein it encodes
Examples of factors which can induce mutations include:
Agents which increase the rate of genetic mutations are called mutagens, and can lead to the formation of genetic diseases
- Mutations can be spontaneous (caused by copying errors during DNA replication) or induced by exposure to external elements
Examples of factors which can induce mutations include:
- Radiation – e.g. UV radiation from the sun, gamma radiation from radioisotopes, X-rays from medical equipment
- Chemical – e.g. reactive oxygen species (found in pollutants), alkylating agents (found in cigarettes)
- Biological Agents – e.g. bacteria (such as Helicobacter pylori), viruses (such as human papilloma virus)
Agents which increase the rate of genetic mutations are called mutagens, and can lead to the formation of genetic diseases
- Mutagens which lead to the formation of cancer are more specifically referred to as carcinogens