Causes of Mutations: Errors in DNA replication

Question 1

How often do errors in DNA replication occur?

Answer 1

• DNA polymerase makes mistake approx. 1 per 100,000 bases added

Question 2

How errors in DNA replication is usually fixed?

Answer 2

Most are corrected by proofreading function of polymerase
- If not, then by post replication mismatch repair process

Question 3

Probability of mutation from DNA replication

Answer 3

10^-10 per base per replication

Question 4

Base substitution in DNA replication

Answer 4

Base in DNA can exist in tautomeric and ionized form

• The imino form of C or A pairs with the amino form of A or C
• The enol form of T or G pairs with the keto form of T or G

Tautometric shift during replication can cause mutation

Question 5

Insertions + Deletions

Answer 5

• Created when bases in template or new strand slip out of alignment
• Most freq. occurs during replication of repetitive DNA sequences ]
• Trinucleotide repeats ae cause of many diseases

Question 6

DNA repeats in disease

Answer 6

• Huntington’s disease and Fragile X syndrome are the result trinucleotide repeat expansions

Question 7

DNA Repeats in Evolution

Answer 7

Expansion and retraction of repeats within coding sequences play a part in ‘rapid’ evolution

Question 8

DNA repeats in behaviour and crime

Answer 8

• Contribute to physiological + behavioural traits
• Basis of modern DNA profiling techniques