AP Bio Chapter 17 Part 2 Flashcards
How did messelson and stahl prepare their experiment?
Grew E. coli bacteria in heavy and light nitrogen
After Watson and crick, what did scientists wonder, and what were the 3 hypotheses
How DNA copied itself
Semi conservative
Conservative
Dispersive
Where do the nitrogen isotopes go when spinned in a centrifuge
DNA w heavy goes to bottom
DNA w light stays on top
What helps figure out the amount of each nitrogen isotope
The densities of DNA
What did meselston and stahl’s experiment investigate?
How DNA splits itself, then adds a new template strand
Describe prokaryotic DNA
Circular
Not packed w proteins like chromosomes
How does prokaryotic DNA replicate and form how many origins
An enzyme grabs it, (DNA polymerase is responsible for DNA synthesis) 1 origin (1 fork/bubble)
How many origins does eukaryotes have, and what’s the deal w their bubbles and forks
Multiple forks and bubbles
2 origins
of forks ______________ #of bubbles
Doubles
What are the 3 parts of DNA replication
Initiation
Elongation
Termination
Helicase
Enzyme that “untwists” the helix at the replication forks, separating the two parental strands and making them available as template strands
Initiation can only begin at specific ___________ which are
Origins, specific locations on a chromosome
Topiomerase
Rotates DNA to decrease torque (which would shred the helix)
Relieves strain
SSBPs
Single strand binding proteins
Bind to unpaired DNA strands
Keep strand open, keep from repairing
Primase
Enzyme that puts down a small RNA primer which is necessary for DNA polymerase to bind at the origin
The addition of nucleotides to a new strand of DNA
Autocatalytic
Nucleotides are automatically added to the ____________ and is determined by
I3’ end of DNA
Sequence of nucleotides in the opposite strand
What is the only direction DNA can elongate in
5’ to 3’
What is the only end nucleotides can be added in
3’
Adding nucleotides is _______________ there are a bunch of nucleotides, and
Self catalyzing
The right one binds
What’s the second part of DNA replication
Elongation
During elongation, what direction are nucleotides added to the strand of DNA
5’ to 3’
What is DNA’s issue
Anti parallel
Both strands have opposite 5’ to 3’ orientations
How can the leading strand of DNA be made
As the replication machinery moves along the chromsome, only one strand can be made in a continuous 5’ to 3’ piece. Only 1 primer is required to synthesize the entire leading strand.
How is the lagging strand made and what are the results called
The other strand is made in smaller, discontinuous 5’ to 3’ segments called Okazaki fragments which are stitched together by the enzyme ligase
Must work away from replication form to elongate.
What is the initial nucleotide chain produced called
A short stretch of RNA, not DNA
Primer, based paired to template strand, new DNA strand will start from 3’ primer end
DNA polymerase
Enzymes that catalyze the synthesis of new DNA by adding nucleotides to a preexisting chain. Requires a primer, which it adds nucleotides to, complementary to existing parental DNA template.
Each Osakaki fragment and lagging strand must be ___________ separately
Primed
How do ligase stitch together Okazaki fragments
Joins together the sugar phosphate backbones of fragments into a continuous DNA strand
What does elongation continue until
Replication bubbles merge
Once replication begins it proceeds in ____ directions from the ________
2 origin
