DNA Flashcards
DNA structure
4 different nucleotides linked by phosphodiester bond
Double helix
Antiparallel
Complementary base pairing
DNA Purines
Adenine and guanine
DNA Pyrimidines
Cytosine and thymine
DNA Complementary base pairing
A=T; G≡C
Hydrogen bonding
DNA structure - review
2 DNA strands wrap around each other
Grooves
Major – proteins interact with nucleotides
Minor – smaller than major groove
DNA size
3.4 nm for 1 turn 10 bp = 1 turn 1 bp = 0.34 nm 1000 bp = 1 kilobase (kb) 1,000,000 bp = 1 megabase (Mb
DNA Replication
Semiconservative replication
Semiconservative DNA replication
Use “old” strand as template for “new” strand
Resulting DNA contains ½ “old” and ½ “new” DNA
DNA Replication: Process
5 steps
Unwind DNA; stabilize ssDNA Primase adds RNA primer to DNA template DNA polymerase III adds nt (5’3’) DNA polymerase I removes RNA primer; adds nuctide DNA ligase links Okazaki fragments
Draw out on chalkboard and/or whiteboard –
1) DNA replication process and
2) How a single nucleotide is added
On page 6. Look at it. I think he drew it on the board
What unwinds the DNA in step 1 of DNA replication
Helicase
What add/remove supercoils in DNA replication step 1
Topoisomerases (Type I, Type II, DNA gyrase (Bacteria))
What releases pyrophosphate (PPi)
in DNA replication step 3
Deoxyribonucleoside triphosphate(s)
Which strand has continuous synthesis in DNA replication step 3
leading strand
it leads the way continuous
Which strand has = discontinuous synthesis in DNA synthesis step 3
lagging strand
What removes RNA primer; adds nucleotide in step 4 of DNA replication
DNA polymerase I
What links Okazaki fragments
DNA ligase
DNA polymerase III
5’ to 3’ polymerase
3’ to 5’ exonuclease
What does the exonuclease do from 3’ to 5’
corrects any mistakes
What does the exonuclease III do from 3’ to 5’
corrects any mistakes
What does the 5’ to 3’ polymerase III do
Adds nucleotides (nt) ~1000 nt/second
DNA polymerase I
5’ to 3’ polymerase
5’ to 3’ exonuclease
3’ to 5’ exonuclease
What do 5’ to 3’ polymerase do
Adds nucleotides
~20 nt/second
What do 5’ to 3’ polymerase I do
Adds nucleotides
~20 nt/second
What do 5’ to 3’ exonuclease I do
Helps remove RNA primer
what do 3’ to 5’ exonuclease I do
Corrects mistake(s)
DNA replication of bacteria begins
Origin of replication (oriC); DnaA binds
DNA replication of eukaryotes begins
Many locations; no oriC
DNA replication of bacteria ends
Terminus
DNA replication of eukaryotes ends
many locations
DNA replication of bacteria both directions
Bidirectional around circular chromosome
DNA replication of eukaryotes both directions
Bidirectional along linear chromosomes
How many replication forks are in bacteria
2
How many replication forks are in eukaryotes
Many
Does bacteria have special structures for DNA replication
NO
What special structures do eukaryotes have for DNA replication?
telomeres
What is a telomere
specialized structure at end of chromosome;
short repeated sequence of DNA
Maintain integrity of linear chromosomes
What are telomeres involved in
aging process by telomere length
cancer by activation of telomerase
What makes telomeres
telomerase
from a RNA template to make DNA
On a linear eukaryotic dna what happens on lagging strand
It cannot finish the strand
Get shortened DNA molecule every time replication occurs
