2.3.2 how DNA replicates

Question 1

DNA polymerase

Answer 1

enzyme that catalyses formation of DNA from activated deoxyribose nucleotides

Question 2

helicase

Answer 2

enzyme that catalyses breaking of hydrogen bonds between nitrogenous pairs of bases in DNA molecule

Question 3

semi-conservative replication

Answer 3

how DNA replicates
- results in 2 new molecules –> each contains 1 old strand & 1 new
- old strand is conserved in each new molecule

Question 4

when does DNA replication occur

Answer 4

during interphase
(before the cell division)

Question 5

to produce a new copy, the DNA molecule must:

Answer 5

1. unwind = double helix is untwisted & catalysed by gyrase enzyme
2. unzip = h bonds between nucleotide bases are broken - catalysed by helicase
   ^^ unzipping results in 2 single strands of DNA with exposed nucleotide bases

Question 6

after unzipping/unwinding, what are the next steps in semi conservative replication

Answer 6

3. free phosphorylated nucleotides (in nucleoplasm) bond to exposed bases
4. DNA polymerase catalyses
5. leading strand synthesised continuously & lagging strand is in fragments that are later joined (catalysed by ligase)
6. hydrolysis of activated nucleotides (release extra phosphate groups) = supplies energy to make phosphodiester bonds

Question 7

which direction does DNA polymerase catalyse the addition of new nucleotide bases

Answer 7

5’ to 3’ direction

Question 8

product of semi-conservative replication

Answer 8

• 2 DNA molecules identical to each other/parent molecule
• each contain 1 old strand & 1 new strand

Question 9

what other DNA replicates semi-conservatively

Answer 9

• loops of DNA in prokaryotes
• inside mitochondria/chloroplasts

Question 10

how is the chance for mutation significantly reduced during replication

Answer 10

there are enzymes which proofread & edit out potential incorrect nucleotides

Question 11

what are alleles/gene variants

Answer 11

different versions of particular gene