DNA profiling

Question 1

Genome

Answer 1

All genetic material of an organism

Question 2

Exon

Answer 2

DNA that codes for a protein, coding region

Question 3

Intron

Answer 3

DNA/RNA that doesn’t code for proteins- interrupts gene sequence, non coding region

Question 4

Satellite DNA

Answer 4

Short sequence of DNA thats repeated lots

Question 5

Minisatellite

Answer 5

20-50bp’s that are repeated over 50 times

Question 6

Microsatetlite

Answer 6

2-4bp’s that are repeated 5-15 times

Question 7

Where do satellites occur + what do they show?

Answer 7

Appear in same position on chromosome, but number of repeats varies between individuals.

Similar satellite patterns=closely related

Question 8

Explain the steps of producing a DNA profile

Answer 8

1. EXTRACT THE DNA, taken from tissue sample may be amplified by PCR
2. DIGESTING THE SAMPLE, restriction endonucleases cut DNA into smaller pieces
3. SEPARATING THE DNA FRAGMENTS, uses electrophoresis
4. HYBRIDISATION, fluorescent /radioactive DNA probes added in excess to DNA fragments
5. VIEWING THE EVIDENCE, fluorescent= use UV light
   Radioactive= use x-ray images

Question 9

What is a restriction endonuclease?

Answer 9

Enzyme that cuts DNA into smaller pieces

Many types that cut at different specific nucleotide sequences

Make 2 cuts, 1 through each strand of DNA double helix

Gives ability to cut DNA at specific introns

These enzymes keep the satellite in tact

Question 10

What is electrophoresis?

Answer 10

A way of utilising the way charged particles move in a gel medium under the influence of an electrical current

Question 11

Explain the steps of electrophoresis

Answer 11

1. Gel placed in a tank containing buffer solution which conducts electricity and maintains pH
2. DNA samples are put into wells, a DNA ladder is also added for comparison
3. A negative electrode is placed near the samples, positive electrode at other end
4. When current is turned on, DNA moves towards the positive electrode because its negatively charged
5. Smaller fragments move more quickly as they have less friction, results in bands at different positions
6. Single strand DNA is then transferred to nylon membrane via southern blotting

Question 12

What is southern blotting?

Answer 12

Nitrocellulose / nylon membrane placed over gel

Its covered with paper towels then left overnight for the single strand DNA to transfer

Transfers because the alkaline solution with DNA is drawn through membrane via capillary action

Question 13

What is a DNA probe?

Answer 13

Short DNA/RNA sequences complimentary to a known sequence

They bind to complimentary strands of DNA

Question 14

What does a DNA probe identify?

Answer 14

The microsatellite regions that are more varied than the other minisatellite regions

Question 15

What is a primer?

Answer 15

Short nucleic acid sequence which is complimentary to the start and end of the target dequence to be amplifed

Question 16

Explain the process of Polymerase Chain Reactions (PCR)

Answer 16

1. 90 degrees to denature H+ bonds holding strands together, to separate strands
2. 55 degrees so primers bind to end of DNA strands, needed for replication
3. 75 degrees, optimum for DNA polymerase which adds the complimentary bases to the primer, identical to og strand. Taq polymerase is involved

Question 17

What is taq polymerase?

Answer 17

A thermophilic hot spring bacteria that prevents enzyme denaturation during heating stage that separates the new DNA strand

Question 18

What does PCR do?

Answer 18

Replicates DNA, producing more than original sample

Question 19

What does a PCR machine contain?

Answer 19

Excess of nucleotide bases A, T, C, G

Small primer DNA sequences

DNA polymerase

Question 20

What are the uses of DNA profiling?

Answer 20

Forensics
Paternal tests
Identification of individuals at risk of certain genetic disease
Determine evoloutionary relationships