2.1.3 Nucleotides and Nucleic Acids – Semi-Conservative Replication Flashcards
(11 cards)
How do dividing cells ensure each the daughter cell receives an exact copy of the genetic material from the parent?
The DNA is replicated/copied.
During what phase of the cell cycle does DNA replication occur?
During interphase
Before DNA can replicate it has to be ‘unzipped’, what is the name of the enzyme that does this?
DNA helicase
Once DNA has been unzipped the two strands act as template strands, what binds to them to make the new strands?
Free nucleotides
What do the free nucleotides have to be in order to bind to the template strands?
They have to be complementary.
Which enzyme joins together one nucleotide with its neighbouring nucleotide?
DNA polymerase
Why is DNA replication called semi-conservative?
As it results in one strand from the original DNA and one that is newly formed.
Why is complementary base pairing needed?
It ensures the same sequence of nucleotides is produced, therefore conserves genetic information. It also prevents the occurrence of random, spontaneous mutations.
Which two scientists were responsible for providing evidence to support semi-conservative replication?
Meselson and Stahl.
What were the 2 fundamental pieces of knowledge possessed which led to evidence for semi-conservative replication?
They knew that all the bases in DNA contain nitrogen and that nitrogen has two forms, a light 14N and heavy 15N. Also, that bacteria will incorporate nitrogen from their growing medium into any new DNA they make.
What did Meselson and Stahl find?
When heavy 15N bacteria were fed lighter 14N and had time to replicate; they found that once the DNA was extracted and centrifuged that the positions of the bands (due to the different weights) supported semi conservative replication.
