DNA Structure and Function Flashcards
What are the four base pairs?
Thymine, Guanin, Adenine, Cytosine
What are Chargaffs Rules?
Different species have different amounts of nitrogensous bases; amounts of A&T and G&C are roughly the same amounts.
Why does the double helix run antiparallel?
One is upside down compared to the other. One runs 5’ to 3’, the other 3’ to 5’.
How many hydrogen bonds do A and T form?
2
How many hydrogen bonds do C and G form?
3
What are histones?
Proteins around which DNA wraps itself to form nucleosomes. Histones are positively charged because DNA is negatively charged. Help prevent DNA from untangling.
What is a nucleosome?
About 150 DNA basepairs wrapped around a histone.
What bonds do nucleic acids use?
Glycosodic
In which direction is the leading strand replicated?
5’ to 3’
In which direction is the lagging strand replicated?
5’ to 3’ in Okazaki fragments.
What is on the 3’ of a DNA strand thats important?
A free 3’ hydroxyl group for RNA primase to attach.
What are the 7 main enzymes associated with DNA replication?
Helicase; topoisomerase; single-strand binding proteins; RNA primase; DNA polymerase I and III; DNA ligase
What does the enzyme helicase do?
UNZIPPING ENZYME. Unwinds original DNA by breaking hydrogen bonds holding them together.
What does enzyme topoisomerase do?
Prevents super coiling of DNA double helix AHEAD OF replication fork.
What is a telomere?
Six base pair sequence at ends of linear chromosomes. Code for nothing. Get shorter as cell divides (aging). Maintained by telomerase.
What is the enzyme telomerase?
Maintains telomeres. Not generally active in adults.
What do the enzymes called Single-strand binding proteins do?
Bind to single strand DNA to prevent helix from reforming.
What does the enzyme RNA primase do?
Synthesizes an RNA primer that attaches to 3’ end to begin DNA replication.
What does the enzyme DNA polymerase I do?
Replaces RNA primer with DNA.
What does the enzyme DNA polymerase II do?
The BUILDER. Replicates DNA strand by adding complementary nitrogenous bases to new daughter strand.
What does the enzyme DNA ligase do?
Seals gaps between okasazki fragments into a single DNA molecule with phosphodiester bonds.
What is DNAs monomer?
nucleotides
What are nucleotides made out of?
Sugar molecule, phosphate group, and a nitrogenous base.
What is a mismatched repair?
Incorrectly added base is detected after replication. Proteins detect and remove base from new strand by nuclease action.
