topic 8 learn and churns

Question 1

explain how the structure of DNA is related to its functions (6 marks)

Answer 1

1. sugar-phosphate backbone/double helix/strength/protects bases and hydrogen bonds
2. long/large molecule so can store lots of information
   3.helix/coiled so compact
3. base sequence allows information to be stored/base sequence codes for amino acids
4. double stranded so replication can occur semi-conservatively/strands as templates/complementary base pairing
5. weak hydrogen bonds for replication/strand seperation

Question 2

describe how altered DNA may lead to cancer (6 marks)

Answer 2

1. DNA altered by mutation
2. mutation changes base sequence
   3.of gene controlling cell growth/oncogene/that monitors cell division
   4.of tumour suppressor gene
3. change protein structure/non-functional protein/protein not formed
4. tumor suppressor genes produce proteins that inhibit cell division
5. uncontrolled rapid mitosis
6. malignant tumour

Question 3

describe how an antibody gene could be isolated from an animal cell and introduce into a crop plant such as maize (4 marks)

Answer 3

1. antibody gene located using gene probe
   2.cut using restriction enzyme
2. at specific base pairs
3. leaving sticky ends
   5.cut maize/dna/vector using same restriction enzyme
4. join using DNA ligase
   7.introduce vector/recombinant DNA to maize

Question 4

describe how bacteria may be produced which have the resistance gene in their plasmids (6 marks)

Answer 4

1. cut desired gene from DNA of oat plant
2. using restriction endonuclease
   3.cut plasmid open
3. with same restriction endonuclease
4. sticky ends/unpaired bases attached
5. use DNA ligase to join/litigation
6. return plasmid to bacterial cells
7. using calcium/electric shock

Question 5

explain how modified plasmids are made by genetic engineering and how the use of markers enable bacteria containing these plasmids to be detected (6 marks)

Answer 5

1. isolate wanted gene/dna from another organism
2. using restriction endonuclease/reverse transcriptase to get DNA and produce sticky ends
3. use ligase to join the wanted gene to plasmid
4. also include marker gene
5. add plasmid to bacteria to grow colonies then replica plate onto medium where the marker gene is expressed
6. bacteria/colonies not killed have antibiotic resistance gene and probably the wanted gene

Question 6

the PCR can be used to produce large quantities of DNA. describe how PCR is carried out (6 marks)

Answer 6

1. DNA heated to 90-95oC
2. strands seperate
   3.cooling to below 70oC
   4.primers bind
   5.nucleotides attach
   6.by complementary base pairing
   7.temperatute 70-75oC
3. DNA polymerase joins nucleotides together
   9.cycle repeats

Question 7

describe how genetic fingerprinting may be carried out on a sample of panda DNA (6 marks)

Answer 7

1. DNA is cut
2. using restriction enzyme
   3.use electrophoresis
   4.seperate according to length/mass
   5.southern blotting/transfer to nylon membrane
   6.make single stranded
   7.apply probe
   8.radioactive or fluorescent
   9.reference to tandom repeats/VNTRs

Question 8

explain how the use of a gene probe could enable the presence of a mutant allele of the cystic fibrosis gene to be detected (4 marks)

Answer 8

1. probe will attach to mutant allele
2. attaches to one dna strand
3. as a result of complementary base pairing
4. radioactive detected on film/x ray (if mutant allele present