Gene Mutations

Question 1

What is a gene mutation?

Answer 1

alteration in nucleic acid sequence of organism’s genome. (~37 trillion gene mutations a day)

Question 2

What is recombination?

Answer 2

alteration to structure of large parts of whole chromosomes

Question 3

How do mutations arise - during replication?

Answer 3

errors cause point mutations which may or may not have an effect, replication slippage where polymerase keeps replicating the same sequence, frame shift which can be a big problem.

Question 4

How do mutations arise - radiation?

Answer 4

UV causes dimerisation of adjacent pyrimidines (esp. thymine) usually resulting in deletion mutation when modified strand copied. ionising -> gamma + x-rays, neutron, beta, + alpha particles, background radiation all cause direct and indirect DNA damage (from free radicles). OH radicle formed from radiation hitting H2O molecule which then negatively interacts w/ DNA

Question 5

How do mutations arise - chemicals?

Answer 5

asbestos (risk decreasing due to increased knowledge and decreased use) associated w/ mesothelioma development. Smoking has hundreds of thousands of carcinogens. pollution –> risk is increasing. pesticides. red meat and alcohol. chemotherapy -> doesn’t just affect cancer cells.

Question 6

How does the body prevent mutations?

Answer 6

melanin protects DNA in skin, dead cells + keratin layer at top of skin for extra protection, antioxidants neutralise radicals.

Question 7

What are peroxisomes?

Answer 7

organelle that makes antioxidant enzymes

Question 8

How does the body get antioxidants?

Answer 8

production by peroxisomes + eating fruit and veg.

Question 9

How does the body repair mutations caused by mutagens?

Answer 9

DNA ligase to repair nicks (small damages to sugar phosphate backbone as phosphodiester bonds have broken), base or nucleotide excision repair (depending on how big damage is) when single stranded damage to bases occur. For double stranded breaks, non-homologous end joining is used.