L5 DNA damage and repair

Question 1

Types of UV damage and its repair

Answer 1

• Pyrimidine Dimer; Nucleotide excision, Direct repair (photolase)
• DNA Strand break; DNA ligase

Question 2

Types of DNA damage

Answer 2

• Replication errors
  -Chemicals
  -UV light
• Ionizing radiation
  -non-ionizing radiation
  -Metabolism

Question 3

Fix for DNA adduct

Answer 3

Removal of molecule from the base by direct repair (alkyltransferase)

Question 4

Pyrimidine Dimer or DNA distortion

Answer 4

Direct repair;photolyase
NER; excision

Question 5

Mismatch

Answer 5

Mismatch repair; removal of the strand and filling up the gaps

Question 6

Cytosine deamination

Answer 6

BER, removal of deaminated base and replacement of correct base

Question 7

Consequences of unrepair DNA

Answer 7

Changes in gene expression which can result in mutated proteins without function of cancer-causing proteins and without tumor suppressing genes, can lead to cell death and cancer.

Question 8

What is Nucleotide Excision Repair and its process.

Answer 8

Removal of nucleotides
1. Endonuclease detection and nick DNA strand
2. Unwinding of DNA
3. Filling of gaps of excised nucleotides

Question 9

What is Base Excision Repair

Answer 9

Removal of base:
1. Damage base detected by glycosylase, bond between base and backbone is cut, leaving behind phosphodiester bond
2. Endonuclease breaks phosphodiester bonds
3.Hole is filled by DNA polymerase I and sealed.

Question 10

Effects od DNA helix distortion

Answer 10

DNA replication becomes challenging, RNA poly& DNA poly unable to determine the base to be paired. Transcription/replication can result in an error in genetic sequence, leading to altered genes or mutated proteins which can lead to the synthesis of mutated proteins that can cause cell death or cancer.