DNA Replication!

Question 1

What is the composition of DNA?

Answer 1

Made up of nucleotides:

• Nitrogen base
• Sugar,
• Phosphate group

Question 2

What defines the polarity of a nucleotide?

Answer 2

The polarity of a nucleotide depends on which end of it’s sugar backbone is sticking out. 3’ OH or 5’ phosphate

Question 3

What is most common nucleotide to least?

Answer 3

A>T>G>C

Question 4

Which is stronger nucleotide bond? Why?

Answer 4

G/C bond is stronger than A/T bond because G/C has 3 H-bonds while A/T has 2

Question 5

How are the two strands of DNA kept a constant distant apart?

Answer 5

Always pairing purine and pyrimidine

Question 6

3 types of replication possibilities, and which is proven to be valid?

Answer 6

• Conservative
• Semiconservative
• Dispersive

Semiconservative is the correct model, proven by taking before and after weight (weighed 1/2 as much)

Question 7

What is necessary for DNA replication to begin? (for dna polymerase to grab hold of )

Answer 7

• A ragged end!!!!

Question 8

What direction does DNA synthesis happen?

Answer 8

5’ to 3’

Question 9

Where on the dna strand does replication start?

Answer 9

Every strand has an origin of replication- a specific spot where replication can be initiated.
Bacteria have 1 and eukaryotes have many

Question 10

Steps of DNA replication

Answer 10

• Helicase unzips the DNA strand
• Primase lays on strand to mark starting point for RNA
  - On leading strand (3’ to 5’), DNA polymerase lays on strand, replicating 5’ to 3’
  - On lagging strand, primers are layed down every few bases so that polymerase can replicate in proper direction. This creates lots of small strands (okazaki fragments)
• Ligase joins the ends of the DNA strands.