Lecture 5: DNA Replication

Question 1

structure of DNA

Answer 1

DNA and RNA are both types of nucleic acids
Store of genetic information
Polymer of nucleotides
Pentose sugar, nitrogenous bases (purines and pyrimidines) and a phosphate group
Double helix (2 strands) held by hydrogen bases (antiparallel)
Pairs adenine-thymine, cytosine-guanine

Question 2

why does DNA replication need to occur before cell division?

Answer 2

DNA needs to replicate before cell division
Semi-conservative replication
Half of the strands of each new DNA molecule are from the original DNA molecule

Question 3

Stages of DNA replication

Answer 3

1. DNA untwists (enzyme DNA helicase breaks hydrogen bonds between bases)
2. Original strand is a template. Free-floating DNA nucleotides are attracted to complementary exposed bases
3. Condensation reactions join the adjacent nucleotides (catalysed by DNA polymerase). Hydrogen bonds form between the bases.
4. Two Strands retwist

Question 4

Gene mutations during DNA replication

Answer 4

DNA replication is carefully controlled to preserve the genetic information
However, changes in the genome do sometimes occur.
These changes are known as mutations.