More On DNA Replication

Question 0

DNA Ligase

Answer 0

Ligare: means to tie

Ligase: used to join new Okazaki Fragments to the growing chain

Question 1

Primers

Answer 1

• DNA Polymerase needs Primers because they can only bind to Double Stranded DNA
• Leading Strand: only needs to be primed once
• Lagging Strand: needs a primer for every Okazaki Fragment
• DNA Primase: makes primers from RNA Nucleotides to avoid mistakes

Question 2

Helicase & Single stranded Binding Proteins

Answer 2

Helicase
>Unzip the dsDNA
>Hydrolyses ATP
>contains both leading/lagging strand helicase
Single Strand Binding Proteins
>Prevent “hair-pins” from connecting to each other

Question 3

Winding Problems

Answer 3

• Every 10 nucleotides = one turn
• Polymerizing 500 per sec = 50 turns
• this would require too much energy

Question 4

Winding Solution

Answer 4

Topoisomers
Type1
>puts a nick in one of the DNA strands (breaks covalent bond)
>allows fragments to spin using less energy
>the stored energy allows the reaction to be reversible
Type2
>Untangles Chromosomes
>breaks double helixes to allow others to pass through, then reconnects them