DNA- Reynolds Flashcards
____ polymerize to form ____and require
monomers, polymers, enzyme and added energy
condensation/ dehydration
Hydrolysis
Condensation: Links monomers to form polymers
Hydrolysis: Polymers broken down into monomers
both can be catalyzed by enzymes
DNA carbons
- 5’
- 3’
- 2’
- 1’
- 5’ C= free phosphate attached to 5’ end, 0-3
- 3’ C= OH attached to the 3’ end
- 2’= nothing (Hs)
- 1’ C = Base
DNA traits
- Two antiparallel strands
- right handed helix
- Hydrophilic phosphate backbone
- Hydrophobic bases in the helix
- dsDNA major and minor grooves
- H bonding btwn bases
7.
Pyrimidine
Purine
Pyrimidine= one ring
Purine= two rings
stabilizing forces of DNA
H bonding
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one ring= pyrimidine
two ring= purine
Pyrimidines
Cytosine
Uracil (RNA)
Thymine (DNA)
Cut the pyi Once
Cytosine
-NH2 top
N=C
pyrimidine
Thymine
(DNA)
=O
- CH3
- NH
Pyrimidines
Uracil
RNA
=O
-HN
CH=CH
pyrimidines
Adenine
-NH2 top
N=C
purine
Guanine
=O (top)
-H2N
purine
Deoxyribosse vs ribose
- Deoxyribose= 2’ carbon has a H
- Ribose= 2’ carbon has an OH
- Nucleoside
- Nucleotide
- Ribonucleoside/ribonucleotide
- Deoxyribonucleoside/deoxyribonucleotide
- Nucleoside- N base + 5’ sugar
- Nucleotide- phosphorylated nucleoside
- Ribonucleoside/tide-OH on 2’
- Deoxyribonucleoside/tide- H on 2’
Bases within a strand linked via
phosphodiester bonds
(btwn 3’ and 5’ carbon)
H bonds bwtn bases…
- A-T 2 H bonds
- G-C 3 H bonds
DNA denatiration when…
hydrogen bonds are disrupted
- Alteration of pH
- Increased heat
- DNA replication
reanneal
complementary DNA strands can reanneal (hybridize)
Tm
temperature that 1/2 of DNA denatures
temp above Tm, DNA is now ss
Hershey and Chase
- virus T2 infects E. Coli
- confirmed that DNA is the genetic material
human nuclear genome is
mito genome is
3.2 billion bp
16,500 bp
Nucleosomes
- DNA associates with histones
- 146 bp of DNA
- then organized to make chromosomes
Meselson and Stahl
- proved DNA replicaiton is a semi conservative process
- Bacteria grown in 14N or 15N medium
DNA synthesis steps
- Occurs at the replication fork and is bidirectional
- Replication fork has leading and lagging (Okazaki fragments) strand synthesis
- Semiconservative
- Proceeds in the 5’ to 3’ direction
- Requires an RNA primer
- Base selected based on H-bonding and geometry
- High fidelity (low error rate)
DNA A
replication initiation factor that promotes denaturation of DNA at the origin of replication
DNA helicase
binds ssDNA near the replication fork and uses ATP to “unzip” DNA
single strand DNA binding protein
keeps DNA single stranded
Topoisoerase
DNA gyrase
- removes torsional strain
- relieve coiling strain and changes the supercoiled form of DNA
Primase
synthesizes RNA primers to prime DNA synthesis
DNA polymerases
replicate DNA
DNA ligase
- links DNA by catalyzing phosphodiester bonds
- joining of Okazaki fragments
- occurs during DNA repair
DNA Synthesis
- DNA is opened via helicase
- ss DNA proteins stabilize single strands
- Topoisomerase relieves twisting forces (torsional strain)
- primase synthesizes RNA primer
- synthesis of leading strand begins (RNA primer leading strand)
- DNA polyerase III 5’→3’ (need primer)
- primase synthesizes RNA primer in the lagging strand
- DNA polymerase III makes Okazaki fragment of lagging strand
- DNA polymerase I removes RNA primer replacing it w/ DNA 5’→3’
- DNA ligase closes gap in sugar phosphate backbone
You are studying DNA replication in your lab and decide to mutate DNA primase. What is the most likely scenario that you will observe?
A. SSBP did not attached to the DNA
B. No replication bubble was formed
C. DNA polymerase III did not attached to the DNA
D. Semiconservative replication occurred …
C. DNA polymerase III did not attached to the DNA
DNA pol I
- 5’→3’ DNA polymerase activity
- 3’→5’ exonuclease activity, proofreading
- 5’→3’ exonuclease activity, RNA primer removal and DNA repair
DNA pol III
- main replication enzyme (many subunits)
- 5’→3’ DNA polymerase activity
- 3’→5’ exonuclease activity mediates proofreading
DNA polymerase adds correct nucleotide via formation of
phosphodiester bond
Leading strands
- DNA synthesized in one long molecule
- DNA primase makes a dingle RNA primer
- DNA polymerase adds nucleotides in 5’→3’
Lagging strand
- synthesized discontinuously
- lagging strand is looped
- DNA polymerase moves away from fork 5’ to 3’ (okazaki fragments)
- Okazaki fragments= RNA primers plus DNA
DNA Damage
- DNA are irreplaceable (RNA and proteins are replacable)
- if damage is not repaired
- point mutation- replacement of one bp
- insertion and deletion mutations
- due to environmental and normal metabilsm