Chapter 2 Mutages

Question 1

Mutagens

Answer 1

Anything that causes a mutation is called a mutagen

Eg) chemicals, toxins, UV Ray’s, radiation

Question 2

Mutagens

3 types

Answer 2

1. Physical - Radiation can break bonds during transcription or translation (eg UV light)
2. Biological - invasive pathogens
3. Chemical - Can affect DNA by swapping bases (eg mustard gas)

Question 3

Mutagens

Chemical

Answer 3

▪ Chemical mutagens usually work by substituting a base in for another.
→ As an exception, others can change the structure of bases or simple “slip in” by resembling a base.

Question 4

Mutagens

Physical

Answer 4

▪ Physical mutagens refer to the various types of radiation that cause damage to DNA.
→ UV light causes structural distortion, cross-linking neighbouring nucleotides.
→ X-rays cause gene and chromosomal aberrations.
→ Nuclear radiation leads to breaks in DNA strands.

Question 5

Mutagens

Biological

Answer 5

▪ Mutations causes by invasive pathogens are called biological agents (mutagens).
→ The pathogen’s DNA becomes permanently integrated with host.

Question 6

Examples of mutagens

Answer 6

HPV Virus
Viral genes insert its self into host gene and causes mutation that stops DNA repair. The infection often causes cancer.

Agrobacteria (a bacterial that cause tumour growth)
This has T1 plasmids that can move into a plant cell. This is called horizontal gene transfer. The T plasmid incorporates its self into host genome. These plasmids are used in GE of plants as a cloning vector.

Question 7

Mutagens are caused by

Answer 7

• Caused by invasion of pathogens eg) bacteria or virus
• Some viruses incorporate into host DNA and they ‘jump around’ the genome. These are called jumping gene or Transposible elements.
• Produces repetitive sections of DNA and accounts for up to half of our genome.
• Some can cause mutations in gene affecting blood clotting - haemophilia