DNA REPLICATION

Question 1

Why is DNA replication important?

Answer 1

So cells get the same number and type of chromosome

Question 2

What does the semi conservative replication of DNA ensure?

Answer 2

Ensures genetic continuity between generations of cells

Question 3

Step 1 of semi- conservative DNA replication:

Answer 3

• DNA helicase breaks the hydrogen bonds between complementary base pairs
• DNA needs to be partially unzipped because otherwise bases are exposed for a long period of time

Question 4

Step 2 of semi- conservative DNA replication:

Answer 4

• each exposed polynucleotide strand acts as a template where complementary free DNA nucleotides bind by the specific base paring rule- e.g. C-G

Question 5

Step 3 of semi- conservative DNA replication:

Answer 5

• nucleotides are joined to their complementary bases on the template strand by hydrogen bonds
• the formation of phosphodiester bonds between these new nucleotides in a condensation reaction catalysed by the enzyme DNA polymerase to form the new replicated DNA strand

Question 6

Step 4 of semi- conservative DNA replication:

Answer 6

• both of the DNA molecules now contain one of the original DNA trends and one new DNA strand composed of the free DNA nucleotides
• but it is identical to the previous strand thanks to the complementary base pairs

Question 7

DNA replication is….

Answer 7

• semi conservative
• each strand in the double helix acts as a template for synthesis of a new, complementary strand

Question 8

What direction does DNA polymerase work in?

Answer 8

3’ to 5’ direction on the template strand, it cannot work continuously on the lagging strand (which rubs 5’ to 3’) so it works against the direction of helicase and forms separate strands of joined DNA strands called OKASAKI FRAGMENTS
- DNA ligaments joins together these fragments to form a fully synthesised new DNA strand