DNA profiling and techniques

Question 1

What are the three techniques used to study genes?

Answer 1

PCR
Gel electrophoresis
Cutting out DNA using restriction enzymes

Question 2

What does PCR do?

Answer 2

amplify millions of copies of a DNA fragment

Question 3

What is placed in the reaction mixture for PCR?

Answer 3

excess nucleotide bases, the DNA sample, primers and DNA polymerase

Question 4

What is a primer?

Answer 4

short sequence of bases that are complementary to the bases at the start of the fragment you want

Question 5

What is the first stage of PCR?

Answer 5

DNA mixture is heated to 95*C to break hydrogen bonds between the two DNA strands

Question 6

What happens after hydrogen bonds in DNA break during PCR?

Answer 6

temperature is decreased to 55*C and primers bind to the ends of the DNA strands

Question 7

What is it called when the primers bind to the end of DNA strand?

Answer 7

annealing

Question 8

What happens after primers have bound to DNA in PCR?

Answer 8

reaction mixture is heated to 72*C so that DNA polymerase can work and add bases to the primer building up the complementary strand.

Question 9

What does gel electrophoresis do?

Answer 9

separates out DNA fragments, RNA fragments or proteins dependant on their size

Question 10

What is the gel tray made of?

Answer 10

solidified agarose gel

Question 11

Where does the gel tray go?

Answer 11

in the gel box with the wells closest to the negative electrode (cathode)

Question 12

How is pH maintained in the gel plate/box?

Answer 12

cover in a buffer solution

Question 13

How can you provide a reference for fragment sizing in gel electrophoresis?

Answer 13

add DNA fragments of known length into first and last well so that you can then compare it to the rest

Question 14

What happens when an electrical current is passed through the gel?

Answer 14

DNA fragments move towards the anode as they are negatively charged

Question 15

How are DNA fragments separated on the gel plate?

Answer 15

smaller fragments move faster and travel further through the gel so they separate due to size

Question 16

What is done after the current is turned off in gel electrophoresis in order to expose the bases?

Answer 16

the gel is placed in an alkaline buffer solution to denature the DNA fragments, exposing the bases

Question 17

What is Southern blotting?

Answer 17

the technique by which DNA strands are passed onto a nylon membrane in the same positions as they were on the gel

Question 18

How are DNA strands cut into small fragments?

Answer 18

use of restriction endonucleases

Question 19

What is the name given to short non coding pieces of DNA that are repeated many times?

Answer 19

satellite DNA

Question 20

What is a minisatellite?

Answer 20

a region of 20-50 base pairs that are repeated several hundred times, also called variable number tandem repeats

Question 21

What is a microsatellite?

Answer 21

2-4 base pairs repeated 5-15 times, also called short tandem repeats

Question 22

How are the fragments on the nylon membrane tagged?

Answer 22

use of a radioactive or fluorescent DNA probes that bind to the DNA fragments and then can be viewed under UV light or X-ray

Question 23

What can DNA profiling be used for?

Answer 23

forensic science and medical diagnosis

Question 24

How can DNA profiling find people at risk of certain diseases?

Answer 24

certain non coding microsatellites are associated with increased risk of disease, these regions can be identified in DNA profiling

Question 25

Why use non coding regions when profiling a human?

Answer 25

genome is very similar, coding sequences would not provide a unique profile and non coding regions contain the short tandem repeats