DNA Part 2 Flashcards
Define semi conservative replication
New DNA double helix is made of one original ‘parent’ strand, and one new ‘daughter’ strand of nucleotides
Who verified semiconservative replication
Melselon & Stakl used equilibrium density-gradient centrifugation
What is another word for new strand
Nascent
What are the three enzyme activities of DNA Polymerase 1?
1) 5’-3’ polymerase 3( adds nucleotides)
2) 5’-3’ exonuclease (removes primer)
3) 3’-5’ exonuclease (proofreads & repairs)
What is the location of the replication bubbles
Occurs simultaneously at many sites along a chromosome
Explain how the data collected from Equilibrium Density-Gradient Centrifugation verifies Semiconservative Replication.
It found ratios of 1:1/2:1/4 for hybrids and
0:1/2:3/4 for light
Describe Origin of Replication, & the organisms identified with the
The sites where replication begins
They are found in bacteria and simple eukaryotes(AT-rich sequences)
Is the origin of replication identified in complex life
Not identified in multicellular eukaryotes
Identify the dominant base pairs found in an Origin of Replication, and why these pairs are found.
The dominant base pairs are adenine and thymine. These base pairs are found because they have double hydrogen bond between them and they are easier to break than the triple bond between guanine and cytosine
How many nucleotides are replicated per minute in humans
How fast must the DNA unwind
3,000
DNA must unwind at 3,000 RPM
How many mistakes are per billion nucleotides
And how many mutations are in a set of chromosome per replication
1 mistake per billion nucleotides
3 mutations in a set of chromosomes per replication
How many new mutations are in a child from parents ?
200 new mutations
State the direction Replication proceeds from an Origin of Replication within a Replication Bubble.
Proceeds bidirectionally(both directions) until bubbles meet
What is organism used to study Replication, and why is it used?
E. Coli
Most aspects of replication are similar in prokaryotes and eukaryotes
Identify the Phase in the Cell Cycle where Replication occurs
Occurs in S-phase, during Interphase of the cell
What are the 8 steps for the leading strand?
1) dnaA protein binds to origin
2) dnaA & other proteins from replication bubble
3) DNA helicase(dnaB protein) breaks H-bonds between bases to unwind DNA
4) Single Strand DNA binding proteins(SSB) keep separate DNA strands apart
5) New Strand(Nascent) is started by attachment of DNA primase which forms the RNA Primer(-10bp long) attached to template by H-bonds
6) DNA polymerase 3 adds nucleotides to RNA Primer
7) DNA Polymerase 1 removes RNA Primer and replaces it with DNA nucleotides
8) this is a continuous across replication bubble for leading strand(3’-5’ template)
Nucleotides are added based on what
H-Bonds
DNA polymerase needs a what and gets it from who
Needs a free 3’-OH and gets it from RNA Primer
Definition replicon
Segment with origin and 2 termini
State the number of Replicons in mammals & how far apart each is.
10,000 replicons and they are separated by 30,000-300,000 bp
Replication occurs in the what direction
Reads template in what direction
New strand is laid out in what direction
Occurs in 5’-3’ direction
Reads template from 3’-5’
New strand is laid down 5’-3’
Differentiate the number of Primases between Prokaryotes and Eukaryotes.
Prokaryotes have 5
- 1, 2, 3, 4, 5
Eukaryotes have at least 15
Identify the length of an Okazaki fragment
100-200 bp fragements
Identify the components of a Primosome
DNA Primase and DNA Helicase
