DNA Replication Flashcards
Who discovered heritable material studying strains of pneumonia?
Frederick Griffith
Who showed early on that heritable material is DNA?
Oswald Avery
Who noted that the ratio of A:T and C:G is 1:1
Erwin Chargaff
Who is given credit for the discovery of the structure of DNA?
Francis Crick, James Watson, Maurice Wilkins, and Rosalind Franklin
What is the backbone of DNA composed of?
Deoxyribose-phosphate
What functional group is at the 3’ end? 5’ end?
Free -OH at 3’; Phosphate group at 5’
What is the relationship of the two DNA strands to each other?
Antiparallel
Adenine is bound to Thymine by how many hydrogen bonds?
2
Cytosine binds to Guanine via how many H-bonds?
3
How are nucleotides in a strand linked?
Phosphodiester bonds
In which direction does DNA synthesis occur?
5’—>3’
What is the name of the pattern of DNA replication?
Semi-conservative
How many origins of replication are located on bacterial chromosomes?
1
What is the initiating step of DNA replication in prokaryotes?
DnaA ATPase recognizes and binds the origin-of-replication sequence and melts the origin open
Following the action of DnaA, what enymes continue to unzip the DNA?
DNA helicases
What prevents the single stranded DNA from reannealing following helicase seperation?
Single-stranded DNA Binding Protein
Which is the only prokaryotic enzyme that can lay down a new strand “from scratch”
Primase
Why are topoisomerases needed?
As the DNA helix is unzipped, the DNA downstream becomes supercoiled and builds up tension
What is the action of Type I Topoisomerases?
Breaking of a covalent bond in the phosphodiester backbone of a single strand of DNA
What is the action of Type II Topoisomerases?
Produces a clean break through a DNA duplex to pass tangled duplexes through each other
What kind of enzyme is DNA gyrase?
Type II topoisomerase
What is the mechanism of antibiotic Ciprofloxacin
Mixed-mode non-competative inhibitor of DNA gyrase
What prokaryotic enzyme synthesizes DNA from the RNA primer in the 5’–>3’ direction?
DNA Polymerase III
On which strand are Okazaki fragments formed?
Lagging strand
What kind of enzymatic activity allows DNA pol III to proofread?
3’–>5’ exonuclease activity
What prokaryotic enzyme “cleans up” by excising all RNA primers and patching resulting gaps with DNA?
DNA Polymerase I
What marks the committed step of cell division in eukaryotes?
The onset of DNA replication
How many origins of replication are located in the human genome?
Hundreds
What eukaryotic enzyme contains primase and initiates DNA synthesis?
Pol alpha
What is the major eukaryotic replication enzyme for lagging strand synthesis?
Pol delta
What is the major eukaryotic replication enzyme for leading strand synthesis?
Pol sigma
What eukaryotic polymerase is used for repair?
Pol beta
What eukaryotic polymerase is only found in mitochondrial DNA?
Pol gamma
What eukaryotic enzyme performs the same action as prokaryotic DNA Polymerase I?
FEN-1 nuclease
What enzyme maintains the length of telomeres in cancer and germ cells?
Telomerase
