A2 DNA Technology study guide 2023 with complete
solution
Starting with mRNA, describe how the process of translation leads to the production of a
polypeptide.
mRNA attaches to ribosome;
codon on mRNA;
binds to an anti-codon on tRNA;
each tRNA brings a specific amino acid;
sequence of codons/bases on mRNA determines order of amino acids;
formation of peptide bonds/amino acids joined by condensation
reactions;
What is meant by a gene?
a length of DNA;
that codes for a single protein / polypeptide;
The polymerase chain reaction (PCR) can be used to obtain many copies of a particular
gene.
(b) Explain how the strands of DNA are separated during the PCR.
by heating;
to break the H-bonds (between complementary bases);
In a particular PCR, two different primers are added to the DNA.
(i) Why are primers required?
to allow the DNA polymerase to attach / start addition of
nucleotides / mark start and end of sequence to be
copied /prevents strands re-joining;
Suggest why two different primers are required.
because the sequences at the ends of the target sequence
are different / one is at the beginning and one at the end;
Describe how a gene can be isolated from human DNA.
use restriction enzyme/endonuclease/named, e.g. Bam/Eco;
to cut DNA in specific place/base sequence
Describe how an isolated gene can be replicated by the polymerase chain reaction
(PCR).
heat DNA to 90 - 95 °C;
strands separate;
add primers;
and nucleotides;
cool so that primers bind to DNA;
(DNA) polymerase forms new strands/joins nucleotides;
Describe how a harmless virus, genetically engineered to contain a CFTR gene, can
be used to insert the gene into a cystic fibrosis sufferer.
virus is inhaled/sprayed into the lungs;
gets into cells, inserting the healthy gene;
Explain why the enzyme is called reverse transcriptase.
makes DNA from RNA
, Describe how genetic fingerprinting may be carried out on a sample of panda DNA.
1 DNA is cut;
2 Using restriction enzyme;
3 Use electrophoresis;
4 Separates according to length/mass;
5 Southern blotting/transfer to (nylon) membrane;
6 Make single-stranded;
7 Apply probe;
8 Radioactive/fluorescent;
9 Reference to tandem repeats/VNTRs/minisatellites;
10 Autoradiography/eq;
Explain how genetic fingerprinting allows scientists to identify the father of a particular
panda cub.
All bands in cub which don't come from mother;
Must be in father's DNA fingerprint;
When pandas are bred in zoos, it is important to ensure only unrelated pandas
breed. Suggest how genetic fingerprints might be used to do this.
Select pairs with dissimilar DNA fingerprints;
Suggest why panda DNA is found in faeces
Cells (from panda) in faeces/gut cells/blood cells;
Explain why the PCR is carried out on the DNA from the faeces
To increase amount of DNA/only small amount present;
Explain why the primers used in the PCR will bind to panda DNA, but not to DNA
from bacteria or bamboo. (line 12)
DNA/primer has specific base-sequence;
Reference to specific/complementary base-pairing;
DNA from wild pandas could also be obtained from blood samples. Suggest two
advantages of using faeces, rather than blood samples, to obtain DNA from pandas.
Taking samples from animals causes stress/injury to animal;
Difficult to find animals;
Pandas are dangerous/threat to human;
Explain
how modified plasmids are made by genetic engineering and how the use of markers
enable bacteria containing these plasmids to be detected.
isolate wanted gene/DNA from another organism/mRNA from
cell/organism;
using restriction endonuclease/restriction enzyme/reverse transcriptase to
get DNA;
produce sticky ends;
use ligase to join wanted gene to plasmid;
also include marker gene;
example of marker e.g. antibiotic resistance;
add plasmid to bacteria to grow (colonies);
(replica) plate onto medium where the marker gene is expressed;
bacteria/colonies not killed have antibiotic resistance gene and
(probably) the wanted gene;
solution
Starting with mRNA, describe how the process of translation leads to the production of a
polypeptide.
mRNA attaches to ribosome;
codon on mRNA;
binds to an anti-codon on tRNA;
each tRNA brings a specific amino acid;
sequence of codons/bases on mRNA determines order of amino acids;
formation of peptide bonds/amino acids joined by condensation
reactions;
What is meant by a gene?
a length of DNA;
that codes for a single protein / polypeptide;
The polymerase chain reaction (PCR) can be used to obtain many copies of a particular
gene.
(b) Explain how the strands of DNA are separated during the PCR.
by heating;
to break the H-bonds (between complementary bases);
In a particular PCR, two different primers are added to the DNA.
(i) Why are primers required?
to allow the DNA polymerase to attach / start addition of
nucleotides / mark start and end of sequence to be
copied /prevents strands re-joining;
Suggest why two different primers are required.
because the sequences at the ends of the target sequence
are different / one is at the beginning and one at the end;
Describe how a gene can be isolated from human DNA.
use restriction enzyme/endonuclease/named, e.g. Bam/Eco;
to cut DNA in specific place/base sequence
Describe how an isolated gene can be replicated by the polymerase chain reaction
(PCR).
heat DNA to 90 - 95 °C;
strands separate;
add primers;
and nucleotides;
cool so that primers bind to DNA;
(DNA) polymerase forms new strands/joins nucleotides;
Describe how a harmless virus, genetically engineered to contain a CFTR gene, can
be used to insert the gene into a cystic fibrosis sufferer.
virus is inhaled/sprayed into the lungs;
gets into cells, inserting the healthy gene;
Explain why the enzyme is called reverse transcriptase.
makes DNA from RNA
, Describe how genetic fingerprinting may be carried out on a sample of panda DNA.
1 DNA is cut;
2 Using restriction enzyme;
3 Use electrophoresis;
4 Separates according to length/mass;
5 Southern blotting/transfer to (nylon) membrane;
6 Make single-stranded;
7 Apply probe;
8 Radioactive/fluorescent;
9 Reference to tandem repeats/VNTRs/minisatellites;
10 Autoradiography/eq;
Explain how genetic fingerprinting allows scientists to identify the father of a particular
panda cub.
All bands in cub which don't come from mother;
Must be in father's DNA fingerprint;
When pandas are bred in zoos, it is important to ensure only unrelated pandas
breed. Suggest how genetic fingerprints might be used to do this.
Select pairs with dissimilar DNA fingerprints;
Suggest why panda DNA is found in faeces
Cells (from panda) in faeces/gut cells/blood cells;
Explain why the PCR is carried out on the DNA from the faeces
To increase amount of DNA/only small amount present;
Explain why the primers used in the PCR will bind to panda DNA, but not to DNA
from bacteria or bamboo. (line 12)
DNA/primer has specific base-sequence;
Reference to specific/complementary base-pairing;
DNA from wild pandas could also be obtained from blood samples. Suggest two
advantages of using faeces, rather than blood samples, to obtain DNA from pandas.
Taking samples from animals causes stress/injury to animal;
Difficult to find animals;
Pandas are dangerous/threat to human;
Explain
how modified plasmids are made by genetic engineering and how the use of markers
enable bacteria containing these plasmids to be detected.
isolate wanted gene/DNA from another organism/mRNA from
cell/organism;
using restriction endonuclease/restriction enzyme/reverse transcriptase to
get DNA;
produce sticky ends;
use ligase to join wanted gene to plasmid;
also include marker gene;
example of marker e.g. antibiotic resistance;
add plasmid to bacteria to grow (colonies);
(replica) plate onto medium where the marker gene is expressed;
bacteria/colonies not killed have antibiotic resistance gene and
(probably) the wanted gene;
