4.3

Question 1

What are gene probes?

Answer 1

Single-stranded sequence of DNA or RNA that is complementary to the nucleotide sequence of a specific gene

Question 2

A gene probe is specifically labelled, i.e. made radioactive or fluorescent and it will bind to a complementary DNA sequence, which will allow it to be

Answer 2

identified

Question 3

One way of using a DNA has

Answer 3

6 steps

Question 4

1st step of using a DNA probe: the DNA to be tested is extracted and if a bigger sample is required then

Answer 4

PCR is used

Question 5

2nd step of using a DNA probe: the DNA is digested into pieces using a

Answer 5

restriction endonuclease

Question 6

3rd step of using a DNA probe: the DNA fragments are separated using a process called

Answer 6

Gel electrophoresis

Question 7

During gel electrophoresis (3rd step) -> DNA is placed in a well in a gel, and an electric current is applied. DNA fragments move towards the positive electrode. The smaller pieces move more quickly through the gel so the pieces of DNA are separated according to

Answer 7

size

Question 8

4th step of using a DNA probe: the gel containing the DNA is treated with an alkali, so that the DNA becomes

Answer 8

single-stranded then transferred to a membrane

Question 9

5th step of using a DNA probe: the gene probe is added to the membrane and

Answer 9

time is allowed for it to bind to its complementary sequence

Question 10

6th step of using a DNA probe: the membrane is washed, if the probe is radioactive -

if the probe has bound to the DNA on the membrane -
if the probe is fluorescent, it will -

Answer 10

• the membrane is placed against a piece of photographic film
• ‘fogging’ will occur on the photographic film
• show up when the membrane is viewed under UV light

Question 11

(GENE LIBRARIES)

A gene library is a

Answer 11

set of thousands of DNA fragments from one organism

Question 12

(GENE LIBRARIES)

1) The DNA of the organism is cut out using a

Answer 12

restriction endonuclease

Question 13

(GENE LIBRARIES)

2) Each fragment is inserted into a plasmid to make a

Answer 13

recombinant plasmid

Question 14

(GENE LIBRARIES)

3)The recombinant plasmids are then inserted into… or alternatively are…

Answer 14

bacterial cells

isolated from cells

Question 15

(GENE LIBRARIES)

4) Reverse transcriptase is used to make a

Answer 15

DNA copy of the mRNA

Question 16

(GENE LIBRARIES)

5) Each piece of DNA is added to a separated plasmid and inserted into a

Answer 16

bacterial cell

Question 17

(GENE LIBRARIES)

6)Each clone of bacteria is stored in a separate well in a

Answer 17

multi-well dish (may be stored for a long time

Question 18

(GENE LIBRARIES)

7) Later, if a particular gene is required, the DNA of the bacteria can be tested using a

Answer 18

gene probe

Question 19

(GENE LIBRARIES)
8) Another way of locating a desired gene is to teach each clone of bacteria using an antibody specific to the protein produced by the

Answer 19

gene of interest

Question 20

(GENE LIBRARIES)

Gene libraries are being used to store genetic material from many different

Answer 20

organisms

Question 21

(GENE LIBRARIES)

If the gene library contains all the DNA from the organism, it is said to be a

Answer 21

representative library

Question 22

(GENE LIBRARIES)
A representative library means that it is highly probable that a specific gene from the organism can be found in at least

Answer 22

one of the fragments