DNA Replication

Question 1

What two types of molecules are required for DNA replication?

Answer 1

Enzymes (helicase and DNA polymerase)
Free nucleotides

Question 2

What is the helicase?

Answer 2

It is often formed from multiple polypeptides and doughnut in shape. Its function is to unwind the DNA helix by breaking the hydrogen bonds. ATP is needs to move along the DNA.

Question 3

What is the DNA Polymerase?

Answer 3

Creates new DNA strands by adding nucleotides one at a time. Requires ATP. The two strands of DNA build in opposite directions.

Question 4

What is polymerase chain reaction?

Answer 4

PCR is direct method of making multiple copies of a desired gene or section of DNA.
Carried out in special thermocycler machines.
Typically, about 30 cycles are used when performing PCR in the laboratory.
PCR is useful in forensic criminal investigations, medical diagnosis, and genetic research and only requires a small amount of DNA to work.
Amplified DNA is run on a polyacrylamide gel using gel electrophoresis.
Gel is stained using ethidium bromide and viewed under UV light to visualize the bands of DNA.
DINA from very small samples of semen, blood or other tissue can be amplified using PCR.

Question 5

What are short tandem repeats?

Answer 5

Within the non-coding regions of an individual’s genome there exists satellite DNA - long stretches of DNA made up of repeating elements called short tandem repeats (STRs)
As individuals will likely have different numbers of repeats at a given satellite DNA locus, they will generate unique
DNA profiles

Question 6

What is Recombinant DNA?

Answer 6

A molecule of DNA composed of genetic material from different sources
Made using restriction enzymes which have the ability to cleave viral DNA (found in prokaryotes)
R.E’s bind to their recognition sites and disrupt the phosphodiester bond between nucleotides,
Via hydrolysis, which in turn disrupts the H-bonds between nitrogenous bases.

Question 7

What is Gel Electrophoresis?

Answer 7

1. DNA samples are taken and amplified with PCR.
2. Restriction enzymes cut DNA into fragments at specific base sequences in each sample.
3. A fluorescent marker binds to a triplet in the DNA fragments, so that results can be seen.
4. The gel is submerged in a buffer solution to maintain pH of the solution.
5. Samples are added to a gel electrophoresis chamber. Electric current is passed through, pushing the fragments along charged electrode by the wells. Since DNA is negatively charged it will travel towards the positively charged electrode and away from the negatively
6. Heavier/larger fragments stay closer to the origin and smaller fragments go further.
7. A banding pattern shows up for each DNA sample and can be compared
8. Once gel elecres under UV light ard ta DNA fragments are made visile by staining the gel with ethidium bromide (which fluoresces undets is tight aled is able to insert itself among the rungs of tailade oel niA).
9. The size of the fragments is then determined using a molecular marker as a standard.