3.9 DNA Replication And The Genetic Code

Question 1

Why does DNA replicate?

Answer 1

DNA replicates itself before cell division so that each new cell has the full amount of DNA, identical to the parent cell. This is important for producing cells needed for growth or repair of tissue.

Question 2

Why is meant by semi-conservative replication?

Answer 2

2 new molecules of DNA are produced. Half of the strands in each new DNA molecule are from the original DNA (ie the new molecule contains on old DNA strand and one new strand)

Question 3

2 enzymes involved in DNA replication? Their function?

Answer 3

DNA helicase: responsible for unwinding and separating the two strands of DNA double helix. It catalyses reactions that break the hydrogen bonds between complementary base pairs

DNA polymerase: catalyses the formation of phosphodiester bonds between the free nucleotides and the newly exposed bases on the template strands

Question 4

How is DNA replicated?

Answer 4

1) DNA helicase causes the hydrogen bonds between the two polynucleotide DNA strands to. Break. The helix unzips too form two single strands
2) Each original single strand acts as template for a new strand. Free-floating DNA nucleotides join to the exposed bases on each original template strands by complementary base pairings - A-T, C-G

3) The nucleotides on the new strand are joined together by the enzyme DNA polymerase, forming phosphodiester bonds between these nucleotides. This forma the sugar-phosphate backbone. Hydrogen bond form between the bases on the new strands and the old strand.
The strands test to form a double helix. Each new DNA molecule contains one strand from the original DNA molecule and one new strand

Question 5

Example of an error that can occur during DNA replication

Answer 5

DNA replication is really curate. However sometimes a random, spontaneous mutation occurs which a is a change to the DNA base sequence