D1.1: DNA Replication Flashcards
State what DNA replication is
The production of exact copies of DNA with identical base sequences.
Outline the purposes of DNA replication.
- to provide a complete copy of the organism’s DNA so that the organism grows from a fertilised egg cell to a large multicellular organism
- repairing damaged tissues
Describe the meaning of “semi conservative” in relation to DNA replication.
the products of DNA replication each contain one of the original DNA strands and one new strand
Explain the role of complementary base pairing in DNA replication.
The complimentary base pairing rule ensures the new strands built are exact copies of the original & genetic code remains intact between generations
- A binds with T
- C binds with G
State why DNA strands must be separated prior to replication.
- each strand of the original DNA molecule acts as a template for the new DNA strands that are being built
Outline the role of helicase in DNA replication.
Helicase is an enzyme attaching to DNA
- It moves along the molecule unwinding the DNA helix and separating the 2 strands by breaking H bonds betw. the bases
Outline the role of DNA polymerases in DNA replication.
- DNA Polymerase III moves along template strand from 3’ to 5’ and assembles new strands of DNA in the 5’ to 3’ direction. Replicates continuously on the leading strand, replicates lagging strand discontinuously.
- DNA Polymerase I removes RNA nucleotides of the RNA primers and replaces them with the correct DNA nucleotides
State the arrangement of DNA polymerase and template DNA for each strand
There are separate DNA polymerases for each stand of template DNA.
State the function of the PCR.
Amplifies a specific DNA sequence, producing multiple copies of it
Outline the process of the PCR, including the use of primers, temperature changes and Taq polymerase.
denaturation phase;
- DNA heated at around 98*C to break the H bonds that hold the 2 strands of the double helix tgt
annealing phase (cooling);
- The sample cools at around 60*C and the short RNA primer sequences bond to complementary sequences in the DNA sample.
extension phase;
- The bonding of RNA primers allows Taq Polymerase to replicate DNA using the RNA primer was a starting point at around 72*C; the DNA polymerases are only able yo extend existing strands and not able to add the first nucleotide of a DNA strand. DNA strands are heated and the process repeats
Process is repeated and the region of interest is amplified exponentially
Deduce the number and relative size of DNA fragments from the number of bands in an electrophoresis gel.
250 to 30k base pairs
Outline the procedure for DNA electrophoresis.
- Gel electrophoresis uses electrical currents to move molecules through a gel
- DNA separated by size and amount of charge
- DNA fragments get digested using restriction endonuclease enzymes which cut the backbone of DNA double helix making shorter DNA segments
- samples of DNA fragments loaded into wells on one end of the gel which is submerged in a buffer solution
- DNA samples begin near negative pole so that they can spread out as they are drawn towards positive pole because PO4 3- group of DNA is negatively charged
Describe how and why DNA fragments separate during electrophoresis.
- samples of DNA fragments loaded into wells on one end of the gel which is submerged in a buffer solution
- DNA samples begin near negative pole so that they can spread out as they are drawn towards positive pole
List applications of the PCR.
- DNA profiling
- Cloning of genes
- Identification of bodies
- To sequence the DNA of extincr species and other life forms
Outline the use of the PCR in testing for viral infection.
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