Limited time offer 20% OFF StudySoup Subscription details

Penn State - MICRB 251 - Class Notes - Microbiology 251: Chapter 5

Created by: Julianna Sickafus Elite Notetaker

> > > > Penn State - MICRB 251 - Class Notes - Microbiology 251: Chapter 5

Penn State - MICRB 251 - Class Notes - Microbiology 251: Chapter 5

0 5 3 43 Reviews
This preview shows pages 1 - 2 of a 3 page document. to view the rest of the content
background image Microbiology 251 
Chapter 5: DNA Replication, Repair, and Recombination
Lectures 1,2
9/21/16-9/25/16
Lecture 1: DNA Synthesis and Machinery -riboses are attached by a phosphate that bridges 3’ and 5’ carbons
-nucleotides are always added from 5’ to 3’
-can only be added to the 3’ end -DNA polymerase builds in a 5’ to 3’ direction -requires primer to begin
-occasionally adds wrong nucleotide
-1 mistake per 100,000 nucleotides -doesn’t correct incorrect nucleotide itself -marks incorrect base
-another enzyme is responsible for the correction
-DNA primase -makes short RNA primers that provide the 3’ OH for DNA  polymerase to start synthesis
-Okazaki fragment:
RNA primer + nucleotides
-connecting fragments involves degrading RNA primer and 
ligating the nick
-RNase H degrades RNA in the heteroduplexed region
-DNA polymerase fills gap (from degraded primers)
-DNA ligase ligates the nick
-ATP used
-AMP released
-DNA helicase -can mechanically separate 2 DNA strands -uses ATP -Single Stranded DNA Binding Protein (SSB) -prevents hairpins from forming in single stranded DNA -even though bases are on same strand, they can still bind  with the correct opposite base if not prohibited from doing so
-sliding clamp protein
-regulates association of DNA polymerases with template
-placed on DNA by clamp loader
-ATP binding opens sliding clamp so DNA can engage
-ADP + P released
-when DNA polymerase unwinds DNA at the fork, the DNA ahead of the
fork overwinds
-produces stress in DNA
background image -topoisomerases (topo’s) -untangles DNA by introducing transient breaks in DNA -topo 1 -1 strand
-cuts 1 spot
-forms covalent bond with DNA backbone
-no ATP needed
-topo 2 -2 strand
-needs ATP
-makes reversible covalent attachment to opposite DNA strands
-both topo’s hold onto DNA so it doesn’t float away and is lost
-strand directed mismatch repair:
-MutS - finds mismatches -MutL -detects nick in new DNA strand -able to tell which strand is newly synthesized -can accurately remove and replace Lecture 2: DNA Replication in Cells -in E. coli: -replication origin is AT rich and associates with initiator proteins -recruit DNA helicase
-AT forms 2 H bonds
-easier to pull apart than 3 between C and G -eukaryotic chromosomes have more than 1 origin of replication -if eukaryotes had 1, chromosome replication would take a  month -some origins are more frequently used than others -some origins are weaker and are used as back ups -each origin of replication has 2 forks with each having a leading and 
lagging strand
-forks merge to form whole chromosome -firing of replication origins regulated by cell cycle
-origin recognition complex (ORC) serves as initiator proteins in 
eukaryotes
-bonded to DNA at all times -only activated by kinase to transition into S-phase -recruits a DNA helicase -also activated by kinase -once origin has fired, ORC remains inactive until cell divides
-cell doubles amount of histones produced

This is the end of the preview. Please to view the rest of the content
Join more than 18,000+ college students at Pennsylvania State University who use StudySoup to get ahead
School: Pennsylvania State University
Department: Microbiology
Course: Molecular and Cell Biology I
Professor: Scott Lindner
Term: Fall 2016
Tags: Microbiology, DNA, and replication
Name: Microbiology 251: Chapter 5, Lectures 1 and 2 Notes
Description: These notes are from chapter 5 lectures 1 and 2 which were on 9/14 and 9/16. They cover DNA replication and repair.
Uploaded: 09/19/2016
3 Pages 19 Views 15 Unlocks
  • Better Grades Guarantee
  • 24/7 Homework help
  • Notes, Study Guides, Flashcards + More!
Join StudySoup for FREE
Get Full Access to Penn State - BMB 251 - Class Notes - Week 1
Join with Email
Already have an account? Login here
×
Log in to StudySoup
Get Full Access to Penn State - BMB 251 - Class Notes - Week 1

Forgot password? Reset password here

Reset your password

I don't want to reset my password

Need help? Contact support

Need an Account? Is not associated with an account
Sign up
We're here to help

Having trouble accessing your account? Let us help you, contact support at +1(510) 944-1054 or support@studysoup.com

Got it, thanks!
Password Reset Request Sent An email has been sent to the email address associated to your account. Follow the link in the email to reset your password. If you're having trouble finding our email please check your spam folder
Got it, thanks!
Already have an Account? Is already in use
Log in
Incorrect Password The password used to log in with this account is incorrect
Try Again

Forgot password? Reset it here