D1.1 DNA Replication Flashcards
What is ‘Watson and Crick’ for?
Evidence that complementary base pairing was key to DNA’s ability to replicate
Why does DNA need to replicate?
- Cell division
- Reproduction
What are the 2 enzymes in replication and what are their jobs?
- Helicase- Breaks hydrogen bonds, unwinds molecules
- Polymerase- forms the phosphodiester bonds in between
What are the 3 different theories for DNA replication?
- Dispersive
- Conservative
- Semi-conservative
Which theory for DNA replication is correct?
Semi-conservative
How does the semi-conservative theory work?
- Hydrogen bonds between bases are broken
- Nucleotides are present
- Pair up with complementary exposed bases
- New strand is linked together
- 2 New DNA molecules are created (1 old & 1 new)
How does gel electrophoresis work?
- uses an electrical current to move molecules through a semisolid medium
- molecules are separated by size, length and amount
DNA and RNA molecules have negative charge so in gel electrophoresis they will move towards…
The positive electrode
Where are the samples of DNA put for gel electrophoresis?
Little wells/ depressions
What is PCR for?
Amplify small segments of DNA for further study or processing
What can PCR be used for?
Vitro cloning
What does vitro cloning require?
- small DNA sample
- DNA polymerase
- primers
- nucleotides
-thermocycler
What is vitro cloning?
Method of copying fragments of DNA
What are the advantages of PCR
- very quick
- does not require living cells
What are some disadvantages of PCR?
- cannot produce mRNA or protein
- can only replicate a small DNA fragment
- expensive
What are some applications of PCR?
- tissue typing
- detecting mutations
- research
- forensic science
What are some applications of DNA profiling?
- forensic science
- maternity/ paternity testing
- analysis of disease
What is a leading strand?
A strand that is replicated in the same direction that the helicase is unwinding (5’ to 3’)
What is the lagging strand?
A strand that is oriented in the opposite direction, does not allow DNA polymerase to move in the same direction as helicase (3’ to 5’)
What is an Okazaki fragment?
A small segment of DNA that is synthesized on the lagging strand during DNA replication
What does DNA ligase do?
Joins Okazaki fragments together
What does gyrase do?
Moves head of helicase, relieving the tension created by the unwinding anf unzipping of the DNA double helix
What does DNA primase do?
Attaches small RNA primers to the template strand
What does polymerase 3 do?
Assembles the new strands of DNA by placing free nucleotides in the correct sequence according to the base sequence of the template strand & the complementary base pairing rule
What does DNA polymerase 1 do?
Removes RNA nucleotides of the primers & replaces them with the correct DNA nucleotides
What does ligase do?
Catalyses the formation of the phosphodiester bonds between the Okazaki fragments
What is DNA proofreading?
Proofreads the newly formed DNA strand as it is being built
