DNA Flashcards
What is a purine?
A and G (double ringed)
What is a pyrimidines?
T and C (single ringed)
What is meant by 3’ and 5’?
The carbon it connects to. 5’ to a phosphate group, 3’ to a hydroxyl group
What are the sides of the DNA ladder made of?
sugar and phosphate.
What are rungs of ladder made of?
nitrogenous bases connected by H bonds
What are 2 main functions of DNA?
expression and replication
Monomers of nucleic acid?
nucleotides
Polymers of nucleic acid?
DNA and RNA
What part of nucleotide contains genetic code?
Nitrogenous bases
The sequence of N bases is __________ for almost all organisms.
different
What is the purpose of DNA replication.
Replication (make proteins), keep it fresh
The location where DNA is unzipped is called . . . ?
replication fork
What is a replication bubble?
The region where 2 rep. forks are close producing a bubble in the DNA.
The ________ strand is made continuously.
leading
The ________ strand is made in short segments called what?
lagging and Okazaki fragments
What is semiconstructive replication?
Produces DNA molecule with 1 new and 1 old strand.
What is constructive replication?
Leaves the original copy in tack and makes a new copy.
What is dispersive replication?
Produces 2 DNA with segments of both old and new.
What is the first step of DNA rep?
Unwinding and separation of parent strand.
Separation is initiated in multiple places.
What enzyme breaks the bonds that connect N bases allowing the double helix to unwind?
DNA helicase
What enzyme relieves tension produced by unwinding DNA?
DNA gyrase
What is the second step of DNA rep?
DNA synthase. Rep begins in different directions on each strand.
What repairs DNA mistakes?
DNA polymerase III and I
Summarize the first half of DNA rep.
The helix is unwound. Single stranded binding proteins prevent it from rewinding. DNA Polymerase III adds triphosphates to help drive the process. The leading strand is built toward the rep fork and the lagging away.
Summarize the second half of DNA rep.
DNA polymerase I excises the RNA primers and replaces them with the right deoxynucleotides. DNA ligase fills the gaps of the lagging strand. Proofreading is done.
What enzyme fills in the gaps between the Okazaki fragments?
DNA ligase
What does DNA ligase use to fill in the gaps between the Okazaki fragments?
Phosphodiester bonds
Why is DNA rep. important for every cell?
mitosis and meiosis
Why is it important to proofread DNA?
A mistake could kill the cell or cause it to malfunction and cause damage.
What is anneal?
The pairing of complementary strands of DNA through H bonding.
What do single stranded binding proteins (SSBs) do?
Keeps separated strands of DNA apart
What base pairs have a double H bond and which have a triple H bond?
A and T have a double
G and C have a triple
What does DNA polymerase take?
Free nucleotides found within cell and adds them to 5’ -> 3’ direction to form new strand.
Which strand is faster?
Leading strand
How does DNA return to original shape?
Once the H bonds are formed again it automatically goes back.
