3.1.5.2 DNA replication Flashcards
1
Q
What does semi-conservative replication of DNA ensure
A
genetic continuity between generations of cells
2
Q
The process of semi-conservative replication
A
1- double helix unwinds 2-strands unzip 3-hydrogen bonds break between complementary bases in the polynucleotide strands └using DNA helicase 4-both strands act as a template 5-free DNA nucleotides align 5-complimentary base pairing occurs - C to G (3 H bonds) and T to A (2 H bonds) 6- hydrogen bonds reform └DNA polymerase joins adjacent nucleotides in the condensation reaction 7- sugar-phosphate back bone forms └using phosphodiester bonds
3
Q
Role of DNA helicase in semi-conservative replication of DNA
A
unwinds DNA and breaks its hydrogen bonds
4
Q
Role of DNA polymerase in semi-conservative replication of DNA
A
joins adjacent nucleotides in the condensation reaction
5
Q
in which direction does DNA polymerase work?
A
3’ to 5’
6
Q
why does DNA polymerase only work in one direction?
A
only complementary to 3’ end of new DNA strand5’ to 3’
7
Q
what direction is the new strand made in?
A
5’ to 3’
8
Q
Semi conservative replication
A
- DNA copies itself before cell division so each new cell has the full amount of DNA
- half of the strands in each new DNA molecule are from the original DNA molecule
9
Q
who provided evidence for semi-conservative replication?
A
Meselson and Stahl
10
Q
what is the experiment that proved semi-conservative replication?
A
- 2 samples of bacteria grown, one in sample containing light nitrogen and one containing heavy nitrogen
- centrifuged out, light on top, heavy on the bottom because its heavy
- heavy nitrogen bacteria replicated in light nitrogen broth
- conservative: DNA with ONLY heavy original strand would settle at the bottom and ONLY light new strands would settle at top
- semi-conservation: DNA with combination of the 2 would settle in the middle
