8.4 Gene Technologies

Question 1

Why does recombinant DNA technology work?

Answer 1

Genetic code is universal
Transcription/translation occur by the same mechanism and result in the same amino acid sequence across organisms

Question 2

What is meant by recombinant DNA technology?

Answer 2

Transfer of DNA fragments from one organism to the other

Question 3

Summarise the process of using reverse transcriptase to produce DNA fragments.

Answer 3

mRNA complementary to the target gene is used as a template
Mixed with free nucleotides which match up to their base pairs
Reverse transcriptase forms sugar-phosphate backbone to create cDNA

Question 4

What is cDNA?

Answer 4

Complementary DNA

Question 5

Summarise the process of using enzymes to produce DNA fragments.

Answer 5

Restriction endonucleases cut DNA at specific sequences
Different REs cut at different points but one RE will always cut at the same sequence
Using particular REs allows you to cut out a certain gene of interest

Question 6

What two ways can DNA fragments be amplified?

Answer 6

In vitro
In vivo

Question 7

What is in vitro?

Answer 7

Polymerase Chain Reaction (PCR)

Question 8

What is in vivo?

Answer 8

Using host cells

Question 9

Describe the reaction mixture in the first stage of PCR.

Answer 9

Contains the DNA fragment to be amplified
Primers that are complementary to the start of the fragment
Free nucleotides to match up to exposed bases
DNA polymerase to create the new DNA

Question 10

Summarise the process of amplifying DNA fragments using PCR.

Answer 10

Heated to break apart the DNA strands
Cooled to allow primers to bind
Heated again to activate DNA polymerase and allow free nucleotides to join
New DNA acts as template for next cycle

Question 11

Summarise the process of inserting a DNA fragment into a vector.

Answer 11

A plasmid is used as the vector
Its cut using the same restriction enzymes as the DNA so that the ends are complementary
DNA ligase joins the fragment and plasmid together

Question 12

What is a plasmid?

Answer 12

Circular DNA from bacteria

Question 13

Summarise the process of inserting a vector into a host cell.

Answer 13

The host cells are mixed with vectors in an ice-cold solution
Heat shocked to encourage cells to take up vectors
The cells can be grown and the DNA fragment will be cloned

Question 14

What is the host cell?

Answer 14

Bacteria

Question 15

What does in vivo DNA amplification do?

Answer 15

Transform cells

Question 16

Summarise the process of identifying transformed cells.

Answer 16

Marker genes
UV light can be used to identify which cells have taken up vector and which haven’t

Question 17

How can DNA probes be used to locate specific alleles?

Answer 17

Designed so that its sequence is complementary to the allele to find
Probes are labelled, amplified using PCR and added to sample of single stranded DNA
Probe will bind if allele is present

Question 18

Give some applications of DNA probes.

Answer 18

Screen someone’s DNA for a heritable health condition
Identify a gene for use in genetic engineering
Predict a patient’s response to a drug

Question 19

What is the purpose of DNA hybridisation?

Answer 19

To measure the degree of difference between two strands of DNA
Can be used to compare DNA to see if a certain gene is present

Question 20

Summarise the process of DNA hybridisation.

Answer 20

DNA strand is labelled and mixed with an unlabelled comparison strand
The more similar the strands, the more strongly they bind and more energy required to break strands apart

Question 21

What are the benefits of genetic profiling?

Answer 21

Can identify heritable diseases early
Treatment can be personalised

Question 22

What is genetic fingerprinting?

Answer 22

A technique used to compare two DNA samples and determine whether they came from the same individual

Question 23

What is meant by VNTRs?

Answer 23

Variable Number Tandem Repeats
The non-coding regions contained in every organism’s genome

Question 24

How does genetic fingerprinting work?

Answer 24

The probability of two individuals having the same VNTRs is low so these areas are compared to see if two DNA samples came from the same organism

Question 25

Summarise the process of genetic fingerprinting analysis.

Answer 25

DNA sample obtained
VNTRs cut out using restriction enzymes, labelled and cloned using PCR
Fragments separated using gel electrophoresis
Banding patterns can be compared

Question 26

How does gel electrophoresis work?

Answer 26

DNA fragments placed at one end of gel slab
Electric current is applied
DNA fragments move towards other end of gel
Shorter fragments travel further
Pattern of bands created is unique

Question 27

Give applications of genetic fingerprinting.

Answer 27

Forensics
Medical diagnosis
Animal and plant breeding