Manipulating Genomes

Question 1

Explain how the automated sequencing machine orders the DNA fragments from the
PCR reaction into the size order (this is capillary gel) (3)

Answer 1

electrophoresis ;
(negatively-charged DNA) moves towards ,
positive electrode / anode ;
smallest/smaller (fragments) move, fastest / faster ; ora
resolution on gel sufficient to register 1, nucleotide /
base;

Question 2

Outline the role of the polymerase chain reaction (PCR) in sequencing a genome (2)

Answer 2

to, amplify / make (many) copies of, DNA ;

(range of) different lengths ;

Question 3

Outline the role of electrophoresis in sequencing a genome (2)

Answer 3

to put DNA pieces in size order ;

to read, base sequence / order of bases ;

Question 4

Outline the role of digestion of DNA by restriction enzymes in sequencing a genome (2)

Answer 4

to cut (genome DNA) into, small(er) / 750 bp, fragments ;
to cut, vectors / BACs / plasmids, (for gene library) ;

Question 5

Suggest why a genome has to be fragmented before sequencing (2)

Answer 5

genome, too big / very large ;
accuracy better / fewer errors (with small fragments) ;
divide job over, time / different labs ;

Question 6

How does the phylogenetic approach to classifying species differ from the biological species
concept? (2)

Answer 6

with phylogenetic approach
no need to test for interbreeding ;
ref. common ancestor / monophyletic groups ;
can apply to organisms that reproduce asexually ;
can apply to, extinct organisms / fossils ;

Question 7

Discuss the potential benefits to mankind and the ethical concerns raised by growing rice modified for increased vitamin A content (‘Golden Rice™’)

Answer 7

B1 reduce vitamin (A) deficiency in named area / ora ;
B2 reduce, eye problems / blindness ;
C1 reduce rice genetic, diversity / variation ;
C2 clone may suffer from one, disease / environmental change ;
C3 hybridisation with wild rice / spread genes to wild populations ;
C4 seeds expensive / need to be bought each year ;
C5 rice may not grow in all areas where needed ;
C6 idea of doubts whether vitamin A content sufficient ;

Question 8

Discuss the potential benefits to mankind and the ethical concerns raised by humans having somatic gene therapy treatment for a genetic disease.

Answer 8

B3 cure / reduce symptoms / better quality of life / less medication;
B4 cystic fibrosis / SCID / Parkinson’s / thalassaemia / LCA ;
B5 extend lifespan / saves lives ;
C7 virus vector may cause (viral) disease ;
C8 procedure may be, invasive / dangerous / painful / stressful ;
C9 temporary / needs to be repeated / limited success ;
C10 immune system / rejection, problems ;
C11 animal testing concerns ;