The cell cycle- replication of DNA Flashcards
what is nuclear division?
process by which the whole nucleus divides, there are two types mitosis and meiosis
what is cell division?
follows nuclear division and is the process where the whole cell divides
what has to happen before the nucleus divides?
its DNA must be replicated
why does DNA need to be replicated before nuclear division?
to ensure all daughter cells have the genetic information to produce the enzymes and proteins they need
how do we know that the DNA replication is very precise?
all the new cells are more or less identical to the original one
what four requirements are needed for semi conservative replication to take place?
- 4 types of nucleotides present with bases A,T,G,C
- Both strands of DNA model act as template for attachment of nucleotides
- Enzyme DNA polymerase needed catalyse reaction
- Source CHEMICAL ENERGY needed drive process
what is the process of semi conservative replication?
- Enzyme DNA HELICASE breaks down hydrogen bonds
- Double helix separates into 2 strands
- Each exposed polynucleotide acts as template for complementary nucleotides to attach
- Energy used to activate nucleotides
- Joined by DNA POLYMERASE
- Each new DNA molecule has 1 original DNA strand and 1 new DNA molecule
what does enzyme DNA helicase do?
break the hydrogen bonds linking the base pairs of DNA
what does the enzyme DNA polymerase do?
join together activated nucleotides
to form the ‘missing’ polynucleotide strand on each of the two original polynucleotide strands of DNA
what was the conservative model?
parental DNA remained intact and separate daughter DNA copy built up from new molecules
1 entirely old, 1 entirely new material
what is the semi conservative model?
DNA splits into 2 separate strands, each of which then replicated its mirror image
each of the 2 new molecules have 1 strand new and 1 strand old material
what is the procedure for the experiment that is evidence for the semi conservative model?
- Bacteria grown in N15 medium- all HEAVY DNA
- Bacteria transferred to medium containing N14 LIGHT DNA
- Samples of bacteria taken after each generation
- DNA extracted and centrifuged
- DNA formed BANDS in tube
what were the results for the experiment that supports the semi conservative model?
- To begin all HEAVY DNA
- 1st generation after transfer N24, all intermediate (hybrid) DNA
- 2nd generation- 50% light, 50% hybrid
- 3rd generation- 75% light, 25% hybrid
