DNA REP

Question 1

Meselson and Stahl

Answer 1

Carried out experiments using nitrogen to determine dna rep is semi conservative

Question 2

Energy for reaction

Answer 2

Is anabolic, nucleotides used are nucleoside triphosphate. p-p-p = high energy for formation of phosphodiester linkage, bonded by dna polymerase 3

Question 3

Origin of rep

Answer 3

The recognition site where the rep starts, all have high AT. Origin binds the pre rep complex, a protein complex that recognises, unwinds and begins to copy

Question 4

Replication

Answer 4

5 to 3 prime, strands anti-parallel. Rep is semi discontinuous with leading and lagging strand, lagging has Okazaki strands

Question 5

Step 1- unwinding

Answer 5

The interaction of proteins with origin provides a short region of ssdna for initiation. Helicase allows the unwinding of dna, binding proteins are used to stabilize

Question 6

2- primer

Answer 6

Polymerase adds nucleotides to 3’ end but needs starter nucleotides so na rna primer is synthesized by primase. The leading strand requires 1 while lagging depends on the number of okazaki fragments. Rna primer has a free 3’ OH to which bond

Question 7

The polymerase complex

Answer 7

Several different dna polymerase molecules engage in dna rep which all account for rate at which polymerization occurs, advancement of DNA pol complex among parent DNA, proofread

Question 8

poly 1

Answer 8

Proof read, repair mismatched bases and remove abnormal bases, repair damage. Reduce error rate from 1 in 10000 to 1 in 100 mil

Question 9

Mitochondrial dna

Answer 9

The difference in nDNA is that it is small and circular not bound to histones. 37 essential genes , 24 containing code to make trna, other 13 for enx=zymer for cell resp