DNA Profiling

Question 1

What is the human genome?

Answer 1

All of the genetic material an organism contains.

Question 2

What are extrons?

Answer 2

Regions of DNA that code for proteins.

Question 3

What are introns?

Answer 3

Large non-coding regions of DNA that are removed from mRNA before it is translated into a polypeptide chain.

Question 4

What is DNA profiling?

Answer 4

When an image is produced of patterns in the DNA of an individual; helps assist in the identification of an individuals familial relationships.

Question 5

What are VNTRs?

Answer 5

Repeating short non-coding regions of DNA (20 to 50 bases) that are unique to an individual.

Question 6

How are VNTRs important in DNA profiling?

Answer 6

The number of VNTR regions are inherited from your biological parent and the more closely related you are to a person the more likely the repeats have similar patterns, the length of the VNTR regions are unique to each individual (apart from identical twins).

Question 7

What are the 5 steps of DNA profiling?

Answer 7

1. Extract DNA.
2. Digesting sample.
3. Separate DNA fragments.
4. Hybridisation.
5. Radioactive/fluorescence.

Question 8

What is the method for producing a DNA profile?

Answer 8

1. DNA must be extracted from a tissue sample, using PCR, the tiniest fragment of DNA can give scientists enough DNA to develop profiles.
2. Strands of DNA are cut into small fragments using restriction endonucleases. Different ‘RE’ cut DNA at a specific nucleotide sequence leaving VNTR’s intact, known as restriction site. All ‘RE’ make 2 cuts, one through each strand of the DNA double helix. ‘RE’ allow the cutting of DNA strands at defined points, leaving intact mini VNTR’s.
3. Electrophoresis is used to separate the cut DNA fragments to form a clear and recognisable pattern. It utilises the way charged particles move through a gel medium with an electric current. Gel is immersed in an alkali to separate DNA double strands into single strands. They are then transferred onto a membrane by Southern Blotting.
4. Radioactive or fluorescent DNA probes are now added in excess to the DNA fragments on the nylon membrane.
5. If radioactive labels are added to probes, x-rays are taken of the membrane. If fluorescent is added to the probes, you place the nylon membranes under UV light and it glows.

Question 9

What are 2 uses of DNA profiling?

Answer 9

1. Forensics: identify suspects of crimes AND to identify bodies or body parts that are unidentifiable.
2. Analysis of disease risk.

Question 10

How are DNA profiles used in forensics?

Answer 10

1. Samples of body cells/fluids are taken from the scene.
2. DNA is removed and profiled.
3. Profile is compared to samples from the suspect, victim and control samples.
4. Care must be taken to avoid contamination of samples.

Question 11

How are DNA profiles used to analyse a disease of risk?

Answer 11

To identify individuals that are at risk of developing particular diseases, certain non-coding satellites have been associated with an increased risk of cancer or a heart disease.

Question 12

What are 2 other ways that DNA profiles used to analyse a disease of risk?

Answer 12

1. To determine the familial relationships for paternity cases or immigration cases.
2. Used in species conservation to help scientists with captive breeding programmes to reduce chances of interbreeding.

Question 13

What are DNA probes?

Answer 13

Short DNA/RNA sequences complementary to known DNA sequences. They bind to complementary strands of DNA under particular conditions of pH and temperature.

Question 14

Why are DNA probes used?

Answer 14

To identify VNTR regions that are highly varied and the excess DNA probes is then washed off.