2.11 - DNA Replication

Question 1

What are two important enzymes?

Answer 1

Helicase and DNA polymerase

Question 3

What is DNA replication?

Answer 3

is semiconservative, meaning that each strand in the DNA
double helix acts as a template for the synthesis of a new, complementary
strand

Question 4

What is the process of DNA replication?

Answer 4

Starts at specific sequence on DNA molecule
DNA helicase unwinds and unzips DNA (breaks H bonds) and forms two seperate strands
New DNA is built from four nucleotides (A, C, G, T) which are abundunant in nucleoplasm
nucleotides attach themseves to base on old strands by complementary base pairing e.g. T-A
DNA polymerase joins new nucleotides to each other by phosphodiester bonds = phosphate-sugar backbone
winding enzyme winds new stands up to form double helices
two new molecules are identical to old molecule (semi-conservative)

Question 5

What did Meselson and Stahl do to find semi-conservative?

Answer 5

They grew the bacteria Escherichia coli with different isotopes of Nitrogen.
The bacteria was exposed to N15 for several generations until it was exposed to a
lighter N14.
Scientists could then distinguish between the different DNA densities by
centrifuging them.