3.9 DNA Replication and the Genetic Code

Question 1

How does DNA replication take place?

Answer 1

1. Histone proteins are removed
2. The DNA double helix is unwound be and enzyme called DNA helicase
3. Hydrogen bonds between strands are broken. This is known as unzipping which is catalysed by helicase
4. Both DNA strands act as a template strand
5. Free nucleotides are activated
6. Free nucleotides form hydrogen bonds with bases on the template strands
7. C bonds with G and A bonds with T. These are complementary base pairings
8. Phosphodiester bonds join nucleotides in the new strands ( catalysed by DNA polymerase

Question 2

Why is DNA replication semi-conservative?

Answer 2

It results in two identical double helixes- generic information is conserved
In each helix one strand is from the original DNA and one is new

Question 3

What are the properties of genetic code?

Answer 3

It is degenerate- several codons can code for the same amino acid
It uses triplet code for the production of not amino acid

Question 4

Genetic code is universal

Answer 4

Genetic code is universal:

- ALL ORGANISMS use the same code (ATGC)

Question 5

How many different triplet/codons can be made?

Answer 5

64

4x4x4