4.2 DNA Replication

Question 1

what is DNA replication (process and what does it result in)

Answer 1

process of copying one DNA double helix into two identical double helices
results in two DNA helicases that are identical to eachtother and to the original molecule

Question 2

where is DNA contained

Answer 2

chromosomes

Question 3

when do cells divide

Answer 3

when the body grows or heals itself

Question 4

what is DNA polymerase

Answer 4

enzyme that carries out DNA replication

• uses each original strand as a template for the formation of a complementary new strand
• positions and joins DNA nucleotides by complementary base pairing
• may add new nucleotides to only one end of the chain

Question 5

why is DNA replication termed semiconservative

Answer 5

a new double helix has one conserved old strand and one new strand

Question 6

what is DNA helicase

Answer 6

enzyme that unwinds and unzips double stranded DNA by breaking the hydrogen bonds between the weak bases

Question 7

what is DNA ligase

Answer 7

enzyme that connects Okazaki fragments and seals any breaks in the sugar phosphate backbone, completes replication

Question 8

describe the 5 steps in DNA replication

Answer 8

1. DNA helicase unwinds and unzips the double stranded DNA by breaking weak hydrogen bonds between the paired bases
2. DNA polymerase positions and joins DNA nucleotides (present in the nucleus) by fitting them into place by complementary base pairing
3. DNA polymerase may add new nucleotides to only one end of chain because DNA strands are in antiparallel configuration
   DNA synthesis occurs in opposite directions, leading strand follows helicase enzyme, lagging strand results in formation of Okazaki fragments
4. DNA ligase connects Okazaki fragments and seals breaks in the sugar phosphate backbone
5. two double helix moledules identicle to each other and to the original DNA molecule

Question 9

what are Okazaki fragments

Answer 9

short segments of DNA