DNA replication Flashcards
DNA is semi conservative, what does this mean?
It means that each strand in the DNA double helix acts as a template strand for the synthesis of a new, complementary strand.
What are the enzymes involved in DNA replication?
- helicase
* DNA polymerase
Describe the process of DNA replication.
1) Replication starts at a specific sequence on the DNA molecule
2) DNA helicase unwinds and unzips DNA, breaking the hydrogen bonds that join the base pair, and forming two separate strands.
3) The new DNA is built up from 4 nucleotides (A,C,G & T) that are abundant in the nucleoplasm.
4) These nucleotides attach themselves to the bases on the old strands by complementary base pairing
5) DNA Polymerase joins the nucleotides to each other by strong phosphodiester bonds, forming the phosphate-sugar backbone
6) A winding enzyme winds the new strands up to form double helixes.
7) The 2 new molecules are identical to the old molecule,semi conservative
What is the conservative hypothesis?
The complete parent DNA molecule acts as a template for the new daughter molecule, which is assembled from new nucleotides. The parent molecule is unchanged
What is Semi-Conservative hypothesis?
The parent DNA molecule separates into its two component strands, each of which acts as a template for the formation of a new complementary strand. The two daughter molecules therefore contain half the parent DNA and half new DNA (semi-conservative hypothesis).
What did Meselson and Stahl experiment prove?
There experiment provided data that supports the theory of semi-conservative replication.
What were the results of Meselon and Stahl experiments?
The N15 strand is heavy so makes a band low down the tube. High density strand sinks further down the tube.
After one generation
• there was only one band
• This was the 14/15 hybrid
Second generation
• there were 2 bands
• A light chain and a 14/15
