Chapter 16: DNA replication Flashcards
What carries a vast array of hereditary information?
Sequences of bases
Orgins of replication eukaryote vs. prokaryote
Eukaryote can have hundreds of origins
Prokaryotes only have one origin of replication
What direction does replication occur in?
Trick question happens in both directions from origin of replication
Helicases
Enzymes that untwist the double helix at the replication forks
Single strand binding proteins
Bind to and stabilize single-stranded DNA
Held hold DNA strands apart
Topoisomerase
Relieves strain in the DNA ahead of the replication fork
Primase
Adds RNA primer
Short segments of RNA
What end can DNA polymerases add to?
Only 3’ end
DNA polymerases (collective)
Catalyze the elongation of new DNA at a replication fork
Difference between dATP and ATP
ATP has ribose
dATP has deoxyribose
Leading strand
Moves towards the replication fork
Lagging strand
DNA polymerase must work in the direction away from the replication fork
Okazaki fragments
Synthesizes the lagging strand as a series of segments
The segments are then joined together by DNA ligase
DNA Polymerase III
Synthesizes new DNA by adding nucleotides to an RNA primer or a pre-existing DNA strand
DNA Polymerase I
Removes RNA nucleotides of primer from 5’ end and replaces them with DNA nucleotides
DNA ligase
Joins Okazaki fragments
Joins 3’ end of DNA that replaces primer to rest of leading strand of DNA
Mismatch Repair
Repair enzymes and correct errors in base pairing
Nuclease
Cuts out and replaces damaged stretches of DNA
Nucleotide excision repair
Telomeres
Postpone the erosion of genes near the ends of DNA molecules
Telomerase
Catalyzes the lengthening of telomeres in germ cells
Vital so whole genes do not get replaced
Bacterial chromosome
Is a double-stranded, circular DNA molecule associated with a small amount of protein
Interphase and Chromatin
At interphase chromatin is organized in a 10-nm fiber
Later is compacted into a 30-nm fiber
Euchromatin
Loosely packed chromatin
Heterochromatin
Highly condensed chromatin
So condensed that cells have trouble expressing genes
Centromeres and telomeres mostly
What does a lack of telomerase result in?
Reduction in chromosome length
What does the semi-conservative nature of DNA permit for?
Allows for daughter cells to inherit the different nucleotides
Example: In the e. coli problems the daughter cells always inherit the nucleotides
What can fix hypoanthime?
Nuclease
DNA polymerase
DNA ligase
What will a lack of helicase result in?
No replication fork
Polytene Chromosomes
Form by replication without seperation
Histone H1
Is not present in nucleosome bead
Instead it draws the nucleosomes together
Rank the levels of organization from smallest to largest
Nucleosome
30 nm
Looped domain
Transformation in Bacteria
Means external DNA is taking into a cell
What is needed for both prokaryotes and eukaryotes to perform DNA replication?
Primers
Origin of replication
dNTP
Double the amount of DNA
Okazaki fragments have…
5’ RNA
3’ DNA
Which enzyme catalyzes the elongation of DNA
DNA polymerase III
Which enzymes work to repair a thymine dimer
Endonuclease
DNA polymerase I
DNA ligase
Histones charge
Postive
DNA charge
Negative
Tetramers
Two types of tetramers form an octamer
Does DNA contain phosphorous?
Yes
