DNA replication

Question 1

Nucleotide vs nucleoside

Answer 1

nucleotide also contains a phosphate

Question 2

Erwin Chargaff rule

Answer 2

A=T AND C=G (a+tnot equals c+g)

Question 3

What keeps the bases together in DNA

Answer 3

3-5phosphodiester bonds

Question 4

Three major forms of DNA

Answer 4

B-form, right handed
A-form- dehydrated
z-form, lefthanded

Question 5

Hyperchromocity of DNA

Answer 5

ds= lower absorbance

ss= higher absorbance

Question 6

Mitochondrial DNA

Answer 6

circle
one strand being “heavy” (H strand) and ight (the L strand).
Both strands encode genes, although more are on the H strand.
37 genes (2 rRNA, 22 tRNA, 13 polypeptides
The D loop is also the site where most of replication and transcription is controlled.
Genes are tightly packed, with almost no non-coding DNA outside of the D loop
Human mitochondrial genes contain no introns, although introns are found in the mitochondria of other groups (plants, for instance).

Question 7

Prokaryotic DNA Polymerases (E. coli)

Answer 7

Pol I - Gap filing
Pol II - proofreading
Pol III leading strand

Question 8

Eukaryotic DNA polymerase

Answer 8

Pol A:DNA Replication (Primer Synthesis)
POl B: Base excision repair
POL GAmma:Mitochondrial DNA replication/repair
POLsigma: DNA Replication; nucleotide and base excision repair
POl delta: DNA Replication; nucleotide and base excision repair

Question 9

Tautomer formation

Answer 9

A pairing with T, but here A pairs with C, that pairs with G. Mutation happens

Question 10

Initiation

Answer 10

Involved are:
	DnaA·ATP: find Ori
		DnaB (helicase)
		DNA G- Rna primer synthesis
		SSBs

Question 11

Elongation

Answer 11

Leading strand
DnaB (helicase)
DnaG (primase)
DnaC (pol III)

Lagging strand
DnaG/B “primosome”
SSBs
DNA Pol I and III
DNA Ligase

Question 12

Mechanism of DNA Ligase

Answer 12

1. Adenylation of DNA ligase
2. Activation of 5`Phosphate in nick
3. Displacement of AMP seals the nick

Question 13

Termination

Answer 13

Counterclockwise fork

Clockwise fork

Question 14

Topoisomerase

Answer 14

unlink parental strands
Top 1 (no atp)and 2(ATP) in EU
top 1 in pro

Question 15

DNA gyrase

Answer 15

creates supercoils in DNA which stabilizes the DNA (requires ATP)

Question 16

Telomerase

Answer 16

adds DNA sequence repeats to the 3’ end of DNA strands in the telomere regions, which are found at the ends of eukaryotic chromosome

Question 17

The Meselson–Stahl experimen

Answer 17

DNA replication was semiconservative. In semiconservative replication, when the double stranded DNA helix is replicated each of the two new double-stranded DNA helixes consisted of one strand from the original helix and one newly synthesized.

Question 18

Packing of DNA in Eukaryotes
The double stranded DNA is wrapped around each nucleosome twice. Each is made up of Histones which have 2 functions:
1) compact DNA

Answer 18

The double stranded DNA is wrapped around each nucleosome twice. Each is made up of Histones which have 2 functions:

1) compact DNA
2) prevent RNA polymerase from binding to promoter

Question 19

DNA ligase

Answer 19

facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond.