D1.1 - DNA Replication

Purpose of DNA replication

Produce new cells

Semi conservative replication

New strands consist of one original strand and one new strand

Helicase

Breaks hydrogen bonds to unzip DNA

Polymerase

Forms sugar phosphate backbone

PCR

Gene technology that makes billions of copies of DNA

Taq polymerase

Thermostable enzyme that does not denature

Primers

Starting point for polymerase and to which a new DNA is attached

What degrees is used in the 3 stages of PCR

95, 54, 72

Process of PCR

Select DNA sequence to be copied

Raise temp to 95 to separate strands

Lower temperature to 54 degrees to allow binding of primers to DNA

raise temp to 72 to allow rapid DNA replication by Taq polymerase

What is gel electrophoresis used for

Creating DNA profile for comparison

What happens in gel electrophoresis

Billions of DNA copies are cut into small sections using restriction enzymes that cut at a specific section e.g TTCT. Segments are separated through gel using electrical current. Small sections move further

Difference between deoxyriboses and ribose structurally

C2 on deoxyribose has 2 Hs but C2 on ribose has OH and H

What direction does helices break H bonds in

3’ to 5’ end

Polymerase III

Adds nucleotides to primers, checks for errors

What direction are new nucleotides added in DNA replication from the original (leading) strand

5’ to 3’

Draw the replication fork

 

Ligase

Joins Okazaki fragments by forming covalent bonds where the primers are

What enzyme checks for errors in DNA replication (proofreading)

Polymerase III

What end of the new strand are nucleotides added to?

3’

Primase

Adds RNA primers to allow polymerase III to start adding nucleotides

Polymerase I

Removes the RNA primers

DNA gyrase

relives stress in DNA molecule by adding supercoils as it is being unwound