Manipulating genomes

Question 1

what is PCR used for

Answer 1

to select a fragment of DNA and amplify to produce millions of copies

Question 2

describe the polymerase chain reaction

Answer 2

step 1: create a mixture of free nucleotides, primers and DNA polymerase
step2: DNA mixture is heated to 95oc to break hydrogen bonds between bases, the mixture is then cooled to 54oc so that primers can anneal to the strands
step 3: reaction is heated to 72 so DNA polymerase can function and complementary base pairing can occur
step 4: two new copies of the fragment of DNA are formed and the cycle restarts

Question 3

what are palindromic sequences

Answer 3

antiparallel base pairs (base pairs that read the same inapposite directions)

Question 4

what do restriction enzymes do

Answer 4

recognise specific palindromic sequences (known as recognition sequences) and cut (digest) the DNA at these places)

Question 5

how is DNA cut

Answer 5

through hydrolysis reaction

Question 6

Sometimes a cut leaves sticky ends what does this mean

Answer 6

they are small tails of unpaired bases at each end of the fragment which can then be used to anneal the DNA to an other fragment with complementary base pairs

Question 7

Describe the process of electrophoresis

Answer 7

1. agarose gel is poured an left to solidify
2. row of wells is created closest to the negative electrode (cathode)
3. a buffer solution is then added
4. using a micropipette add same volume of DNA into each well
5. add a power supply to create electrical current
6. DNA fragments will move to the positive electrode with smaller pieces moving further and faster
7. remove the gel tray and stain the DNA fragments to make them visible

Question 8

what is electrophoresis

Answer 8

procedure that uses an electrical current to separate out DNA fragments based on size

Question 9

what is DNA profiling used for

Answer 9

forensics and medical diagnosis

Question 9

what is DNA profiling

Answer 9

the number of times a sequence us repeated at different specific places in a persons genome is analysed using electrophoresis

Question 10

what is genetic engineering

Answer 10

the manipulation of an organisms DNA

Question 11

what is recombinant DNA

Answer 11

DNA formed by joining together DNA from different sources

Question 12

how is genetic engineering carried out

Answer 12

1. extract a DNA fragment that contains the desired gene, using restriction enzymes
2. Insert the DNA fragment into vector DNA
3. isolate the vector DNA
4. vector DNA is cut open using restriction enzymes using the same one that was used to isolate the DNA fragment so that the sticky ends are now complementary
5. the vector DNA and DNA fragment are mixed together with DNA ligase which joins the sugar phosphate backbones of the two bits of DNA
6. recombinant DNA is formed
7. the vector with the recombinant DNA is used to transfer the gene into the bacterial cells

Question 13

what is an example of genetically modified plants

Answer 13

soybean plants have been genetically modified to be insect resistant

Question 14

what are the positive and ethical issues concerning GM soybean plants

Answer 14

+ reduce the amount of chemical pesticides used, can be more nutritious
- may encourage monoculture which decreases biodiversity and makes them vulnerable to disease
- could interbreed with wild plants creating weeds resistant to herbicides
-expensive for poorer farmers

Question 15

what is ‘pharming’

Answer 15

using genetically modified organisms like animals to produce pharmaceuticals

Question 15

what are the ethical issues both positive and negative to pharming

Answer 15

+ drugs can be made in large quantities
- could have harmful side effects
-

Question 16

what are the ethical issues with GM pathogens

Answer 16

• potential mass outbreak of disease
• GM version may become more harmful
• could be used for biowarfare

Question 17

what are the positive and negative issues with ownership of GM organisms

Answer 17

+ owner will generate profit from sales
+ encourages competition between scientists leading to faster discoveries
- farmers cannot afford patented GM seeds
- some patents mean that farmers cannot legally plant seeds without paying again

Question 18

what are genetic disorders

Answer 18

inherited disorders caused by abnormal genes

Question 19

what is gene therapy

Answer 19

altering alleles inside cells to cure genetic diseases

Question 20

what is the process for gene therapy if a disease is caused by a mutated dominant allele

Answer 20

‘silence’ the dominant allele

Question 21

what is the process for gene therapy if a disease is caused by a recessive allele

Answer 21

add a working dominant allele

Question 22

what are the two types of gene therapy and what do they involve

Answer 22

somatic- altering the alleles in body cells
germ line- involves altering alleles in sex cells

Question 23

what are some positive ethical issues of gene therapy

Answer 23

• could prolong lives of people with genetic disorders
• could give people better quality of life
• germ line would allow carriers to produce offspring without that disease
• germ line could reduce number of individuals with that disease so less people needed treatment

Question 24

what are some of the negative ethical issues and disadvantages with gene therapy

Answer 24

• technology could be used for other things such as reversing ageing
• could do more harm than good
• expensive
  -body could identify vectors as foreign bodies and begin an immune response
• allele could be inserted into the wrong place
• inserted allele could be overexpressed
• short lived in somatic therapy
• multiple treatments may be needed

Question 25

the chain. termination method was one of the first methods of DNA sequencing, describe how it was carried out

Answer 25

step 1
- add a single stranded DNA template, DNA polymerase, free nucleotides and a fluorescently labelled nucleotide (different one in each tube) to a mixture into four different tubes
step 2
- tubes undergo PCR which produces many strands
step 3
- DNA fragments in each tube are separated by electrophoresis and visualised under UV light

Question 26

if you wanted ti sequence the whole genome of an organism describe the process you would use

Answer 26

1- genome is cut into smaller fragments using restriction enzymes
2. fragments are inserted until bacterial artificial chromosomes (man-made plasmids)
3. BACs are then inserted into bacteria (act bacterium contains a different DNA fragment)
4. bacteria divide, creating colonies of cloned cells that contain specific DNA fragment
5. DNA is extracted from each colony and cut up using restriction enzymes
6. each piece of DNA is sequence using chain termination method
7. pieces are put back in order using computer systems
8. DNA fragments from all the BACs are put back in order by computers to complete the genome

Question 27

what is computational biology and bioinformatics

Answer 27

computational biology- using computers to study biology
bioinformatics- developing computers in order to study and store biological information)

Question 27

how does gene sequencing affect synthetic biology

Answer 27

biological molecules can be made from scratch as sequencing a gene allows the sequence of amino acids for the primary structure of a polypeptide to be predicted