Gene technology questions and answers

Describe the use of recombinant DNA technology in the synthesis of human insulin by bacteria [8]

mRNA coding for insulin/isolate gene for human insulin;
from beta cells of islets of Langerhans/pancreas;
reference to reverse transcriptase;
to cDNA;
reference PCR/DNA polymerase/double strand;
reference sticky ends;
use of vector/virus/plasmid;
reference endonuclease/restriction enzymes;
to cut plasmid;
reference DNA ligase to join DNA;
inserted into suitable host cell/E.coli/bacteria;
reference method of insertion;
identification of modified bacteria;
reference growth/culture of engineered bacteria in fermenters

Describe how the gene coding for human insulin can be obtained and inserted into a plasmid vector. [8]

obtain mRNA from β cells (of islets of Langerhans of pancreas) ;
reverse transcriptase ;
make (single-stranded) cDNA ;
DNA polymerase used to make cDNA double stranded ;
sticky ends created ;
(obtain) plasmids ;
cut with restriction, endonuclease/ enzyme ; A named e.g. EcoR1
ref. complementary sticky ends ;
cDNA / insulin gene, mixed with plasmid ;
DNA ligase ;
seals nicks in sugar-phosphate backbone ;

Explain the advantages of treating diabetic people with human insulin produced by gene technology.[6]

it is identical to human insulin ;
(more) rapid response ;
no/ fewer, immune response/ side effects/allergic reactions ;
ref. to ethical/ moral/ religious, issues ;
cheaper to produce in large volume/ unlimited availability ;
less risk of, transmitting disease/infection ;
good for people who have developed tolerance to animal insulin ;

Explain how bacteria can be genetically modified and then identified using antibiotic resistance genes.[8]

(recombinant) plasmids mixed with bacteria ;
(some) bacteria, take up plasmids/ transformed ;
heat shock / calcium chloride solution/Ca 2+ ions/electroporation ;
to identify bacteria containing plasmids
grow on, agar/medium, containing antibiotic (A) ;
plasmid contains, antibiotic (A)/ ampicillin, resistance gene(s) ;
bacteria with plasmid survive ;
to identify recombinant bacteria
replica plate ;
(onto) agar/ medium, containing second antibiotic (B) ; A tetracycline
resistance gene inactivated (by insertion of new, DNA/ gene

Outline how genetic fingerprinting is carried out [8]
Describe how electrophoresis is used in genetic fingerprinting [8]

ref. to VNTR (sequences) ;
quantity of DNA increased by PCR ;
DNA fragmented by, restriction enzyme(s) / endonuclease(s) ;
loaded (into wells) in agarose gel ;
(at) negative end/ cathode end ;
ref. to buffer/ electrolyte ;
direct current applied ;
phosphate groups of DNA give negative charge ;
(negatively charged) DNA attracted to, anode/ positive electrode ;
short pieces/ smaller mass, move further/move faster ;
(pieces) transferred to, membrane/ nylon/nitrocellulose/ absorbent paper or Southern blotting ;
heated to separate strands ;
probes/ fluorescent dye, added ;
X-ray film/ UV light/ lasers ;
pattern of stripes/ ref. banding pattern ;

Decsribe how genetic screening is carried out in an adult human [8]

samples of cells taken
e.g white blood cells
test for chromosomal abnormalities
e.g Down’s Syndrom
cells cultured so that they divide
stopped at metaphase
use of colchicines
cells made to take up water
chromosomes separated
karyotype produced
flourescent makers to help detect abnormalities
test for particular allele
DNA extracted
DNA cut with restriction enzyme
electrophoresis occurs
to separate DNA into strands
complementary/specific probe(for mutant allele)

Discuss the advantages of screening for genetic conditions[8]

information about the increased risk of person having genetic conditions ;
ref. breast cancer/ named example ;
allows people to prepare for late onset genetic conditions ;
ref. Huntington’s disease/Alzheimer’s disease/named example ;
identify whether fetuses are going to develop a genetic condition ;
so can give early treatment when born ;
allows parents to prepare for the birth of a child who will need treatment for a considerable time or even throughout life ;
identifies carriers of genetic conditions ;
helps to provide early diagnosis ;
allows couples who are both carriers of a genetic condition to make decisions about starting a family/ having more children/ seeking IVF ;

Describe the ways by which gene mutations can occur. [6]

change in, base / nucleotide, sequence (in DNA) ;
during DNA replication ;
detail of change ; e.g. base, substitution / addition / deletion
frame shifts /;
different / new, allele ;
random / spontaneous ;
mutagens ;
ionising radiation ;
UV radiation / mustard gas ;

Explain how genetic diseases may be treated using gene therapy. [6]

normal, gene/ allele ;
(insert into) vector ;
liposomes (as vectors) ;
liposomes in, aerosol/ inhaler ;
liposome fuses with host cell ;
virus (as vector) ;
virus vector harmless ;
short term effect ;
repeat treatments needed ;
side effects ;

Explain how changes in the nucleotide sequence of DNA may affect the amino acid sequence in a protein. [7]

code is three, bases / nucleotides ; triplet code
(gene) mutation ; chromosome mutation
base, substitution / addition / deletion ;
addition / deletion, large effect (on amino acid sequence) ;
frame shift ;
completely new code after mutation / alters every 3 base sequence which follows ;
(substitution) often has no effect / silent mutation ;
different triplet but same amino acid / new amino acid in non-functional part of protein ;
(substitution) may have big effect (on amino acid sequence) ;
could produce ‘stop’ codon ;
sickle cell anaemia / PKU / cystic fibrosis ;
reference to transcription or translation in correct context ;

Explain the advantages and disadvantages of genetic screening in humans.

Advantges
- known risk for next generation;
- allows possible abortion of affected fetus;
- allows sorting of IVF embryos;
Disadvantages
- loss of hope;
- insurance company problems;
- employment problems;
- miscarriage risk;
- trauma of knowledge;

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