AS.020.151 Chapter Notes - Chapter 9: Dna Replication, Nucleic Acid Double Helix, Semiconservative Replication
12 Jun 2018
School
Department
Course
•Use%Chargaff’s%Rule%to%determine%the%percent%A,%T,%G%and%C%content%in%a%DNA%molecule.
•Describe%what%is%meant%by%semiconservative%DNA%replication.
•Explain%the%process%of%DNA%replication,%specifically%with%regards%to%leading%and%lagging%strand%
synthesis%at%a%replication%fork.%Correctly%identify%leading%and%lagging%strands,%and%list%the%main%
enzymes%involved%in%replication%and%their%respective%function(s).
•Describe%the%end%replication%problem%that%occurs%at%the%tips%of%linear%chromosomes,%and%explain%how%
telomerase%helps%to%prevent%the%shortening%of%chromosome%ends.
9.1%DNA%Structure%Reflects%Its%Role%as%the%Genetic%Material
Chargaff- relative%amounts%of%different%nucleotides
Franklin- some%helix
Watson%&%Crick-put%it%all%together%for%overall%structure
A=T
G=C
purines
pyrimidines
Franklin-X%ray%crystallography%(3D%structure%of%DNA)
Key$Features$of$DNA$Structure
Double%helix
1)
Antiparallel
2)
Outer%edges%of%bases%in%major%and%minor%grooves%(binding%sites%for%proteins)
Most%proteins%bind%in%major%grooves
a.
Non-covalent%interactions
b.
3)
Novel$Features
Stores%all%genetic%info
1)
Susceptible%to%mutation
2)
Must%be%precisely%replicated%in%cell%division%cycle
3)
Expressed%as%a%phenotype
4)
9.2%DNA%Replicates%Semi-conservatively
Several%proposed%methods%
Major%groove
Minor%groove
Meselson-Stahl:
DNA%separated%by%density%of%isotopes
Replication
New%DNA%and%RNA%strands%always%extended%
in%a%3'%to%5'%direction
Replication$fork-
-New%daughter%strands%extended%in%opposite
directions%at%the%replication%fork
-Strand%that%grows%into%fork%is%the%leading%strand
Extended%continuously
-Strand%that%grows%away%is%lagging
Extended%discontinuously
Using%smaller%Okazaki%fragments
dNTPs-deoxyribonucleoside%triphosphates,%
building%blocks%of%DNA%synthesis
Removing%two%phosphates%provides%energy%for%
polymerization
Initiation$of$DNA$Replication?
Begins%with%binding%of%proteins%to%origins%of%replication%(ori)
Multiple%ori%in%eukaryotes
Proteins$in$DNA$Replication
The$End$Replication$Problem
Lagging%strands%leave%non-replicated%overhangs%of%parent%DNA
These%are%removed
Telomerase- prevents%shortening%of%chromosome%ends%(telomeres),%has%RNA%sequence%that%acts%as%
template%for%DNA
Repair$of$Replication$Errors
DNA%polymerases%make%mistakes
Proofreading- if%bases%are%paired%incorrectly%as%they%are%added,%the%nucleotide%is%removed
9.3%Mutations%Are%Heritable%Changes%in%DNA
Mutations- changes%in%the%nucleotide%sequence%of%DNA%that%are%passed%on%from%one%cell,%or%
organism,%to%another
Two%classes:
Somatic%mutations- in%non-gamete%cells1)
Germ%line%mutations- occur%in%gamete%cells%(can%be%passed%to%offspring)2)
Unwind%the%DNA
Synthesizes%RNA%primer%sequence
Adds%nucleotides%to%the%growing%chain
Connects%Okazaki%fragments
Chapter%9:%DNA%and%its%Role%in%Heredity
Monday, November 13, 2017
9:54 PM
•Use%Chargaff’s%Rule%to%determine%the%percent%A,%T,%G%and%C%content%in%a%DNA%molecule.
•Describe%what%is%meant%by%semiconservative%DNA%replication.
•Explain%the%process%of%DNA%replication,%specifically%with%regards%to%leading%and%lagging%strand%
synthesis%at%a%replication%fork.%Correctly%identify%leading%and%lagging%strands,%and%list%the%main%
enzymes%involved%in%replication%and%their%respective%function(s).
•Describe%the%end%replication%problem%that%occurs%at%the%tips%of%linear%chromosomes,%and%explain%how%
telomerase%helps%to%prevent%the%shortening%of%chromosome%ends.
9.1%DNA%Structure%Reflects%Its%Role%as%the%Genetic%Material
Chargaff- relative%amounts%of%different%nucleotides
Franklin- some%helix
Watson%&%Crick-put%it%all%together%for%overall%structure
A=T
G=C
purines
pyrimidines
Franklin-X%ray%crystallography%(3D%structure%of%DNA)
Key$Features$of$DNA$Structure
Double%helix
1)
Antiparallel
2)
Outer%edges%of%bases%in%major%and%minor%grooves%(binding%sites%for%proteins)
Most%proteins%bind%in%major%grooves
a.
Non-covalent%interactions
b.
3)
Novel$Features
Stores%all%genetic%info
1)
Susceptible%to%mutation
2)
Must%be%precisely%replicated%in%cell%division%cycle
3)
Expressed%as%a%phenotype
4)
9.2%DNA%Replicates%Semi-conservatively
Several%proposed%methods%
Major%groove
Minor%groove
Meselson-Stahl:
DNA%separated%by%density%of%isotopes
Replication
New%DNA%and%RNA%strands%always%extended%
in%a%3'%to%5'%direction
Replication$fork-
-New%daughter%strands%extended%in%opposite
directions%at%the%replication%fork
-Strand%that%grows%into%fork%is%the%leading%strand
Extended%continuously
-Strand%that%grows%away%is%lagging
Extended%discontinuously
Using%smaller%Okazaki%fragments
dNTPs-deoxyribonucleoside%triphosphates,%
building%blocks%of%DNA%synthesis
Removing%two%phosphates%provides%energy%for%
polymerization
Initiation$of$DNA$Replication?
Begins%with%binding%of%proteins%to%origins%of%replication%(ori)
Multiple%ori%in%eukaryotes
Proteins$in$DNA$Replication
The$End$Replication$Problem
Lagging%strands%leave%non-replicated%overhangs%of%parent%DNA
These%are%removed
Telomerase- prevents%shortening%of%chromosome%ends%(telomeres),%has%RNA%sequence%that%acts%as%
template%for%DNA
Repair$of$Replication$Errors
DNA%polymerases%make%mistakes
Proofreading- if%bases%are%paired%incorrectly%as%they%are%added,%the%nucleotide%is%removed
9.3%Mutations%Are%Heritable%Changes%in%DNA
Mutations- changes%in%the%nucleotide%sequence%of%DNA%that%are%passed%on%from%one%cell,%or%
organism,%to%another
Two%classes:
Somatic%mutations- in%non-gamete%cells1)
Germ%line%mutations- occur%in%gamete%cells%(can%be%passed%to%offspring)2)
Unwind%the%DNA
Synthesizes%RNA%primer%sequence
Adds%nucleotides%to%the%growing%chain
Connects%Okazaki%fragments
Chapter%9:%DNA%and%its%Role%in%Heredity
Monday, November 13, 2017
9:54 PM
•Use%Chargaff’s%Rule%to%determine%the%percent%A,%T,%G%and%C%content%in%a%DNA%molecule.
•Describe%what%is%meant%by%semiconservative%DNA%replication.
•Explain%the%process%of%DNA%replication,%specifically%with%regards%to%leading%and%lagging%strand%
synthesis%at%a%replication%fork.%Correctly%identify%leading%and%lagging%strands,%and%list%the%main%
enzymes%involved%in%replication%and%their%respective%function(s).
•Describe%the%end%replication%problem%that%occurs%at%the%tips%of%linear%chromosomes,%and%explain%how%
telomerase%helps%to%prevent%the%shortening%of%chromosome%ends.
9.1%DNA%Structure%Reflects%Its%Role%as%the%Genetic%Material
Chargaff- relative%amounts%of%different%nucleotides
Franklin- some%helix
Watson%&%Crick-put%it%all%together%for%overall%structure
A=T
G=C
purines pyrimidines
Franklin-X%ray%crystallography%(3D%structure%of%DNA)
Key$Features$of$DNA$Structure
Double%helix1)
Antiparallel2)
Outer%edges%of%bases%in%major%and%minor%grooves%(binding%sites%for%proteins)
Most%proteins%bind%in%major%groovesa.
Non-covalent%interactionsb.
3)
Novel$Features
Stores%all%genetic%info1)
Susceptible%to%mutation2)
Must%be%precisely%replicated%in%cell%division%cycle3)
Expressed%as%a%phenotype4)
9.2%DNA%Replicates%Semi-conservatively
Several%proposed%methods%
Major%groove
Minor%groove
Meselson-Stahl:
DNA%separated%by%density%of%isotopes
Replication
New%DNA%and%RNA%strands%always%extended%
in%a%3'%to%5'%direction
Replication$fork-
-New%daughter%strands%extended%in%opposite
directions%at%the%replication%fork
-Strand%that%grows%into%fork%is%the%leading%strand
Extended%continuously
-Strand%that%grows%away%is%lagging
Extended%discontinuously
Using%smaller%Okazaki%fragments
dNTPs-deoxyribonucleoside%triphosphates,%
building%blocks%of%DNA%synthesis
Removing%two%phosphates%provides%energy%for%
polymerization
Initiation$of$DNA$Replication?
Begins%with%binding%of%proteins%to%origins%of%replication%(ori)
Multiple%ori%in%eukaryotes
Proteins$in$DNA$Replication
The$End$Replication$Problem
Lagging%strands%leave%non-replicated%overhangs%of%parent%DNA
These%are%removed
Telomerase- prevents%shortening%of%chromosome%ends%(telomeres),%has%RNA%sequence%that%acts%as%
template%for%DNA
Repair$of$Replication$Errors
DNA%polymerases%make%mistakes
Proofreading- if%bases%are%paired%incorrectly%as%they%are%added,%the%nucleotide%is%removed
9.3%Mutations%Are%Heritable%Changes%in%DNA
Mutations- changes%in%the%nucleotide%sequence%of%DNA%that%are%passed%on%from%one%cell,%or%
organism,%to%another
Two%classes:
Somatic%mutations- in%non-gamete%cells1)
Germ%line%mutations- occur%in%gamete%cells%(can%be%passed%to%offspring)2)
Unwind%the%DNA
Synthesizes%RNA%primer%sequence
Adds%nucleotides%to%the%growing%chain
Connects%Okazaki%fragments
Chapter%9:%DNA%and%its%Role%in%Heredity
Monday, November 13, 2017 9:54 PM
Document Summary
Chapter 9: dna and its role in heredity. Correctly identify leading and lagging strands, and list enzymes involved in replication and their respective function(s): describe the end replication problem that occurs at the tips of linear chromosomes, telomerase helps to prevent the shortening of chromosome ends. 9. 1 dna structure reflects its role as the genetic material. Watson & crick- put it all together for overall structure purines. Outer edges of bases in major and minor grooves (binding sites for proteins) a. b. Must be precisely replicated in cell division cycle. A molecule. g and lagging strand s, and list the main mosomes, and explain how. New daughter strands extended in opposite directions at the replication fork. Strand that grows into fork is the leading strand. Using smaller okazaki fragments dntps- deoxyribonucleoside triphosphates, building blocks of dna synthesis. New dna and rna strands always extended in a 3" to 5" direction. Begins with binding of proteins to origins of replication (ori)
