gene tech Flashcards
Describe how DNA is replicated in a cell.
DNA strands separate / hydrogen bonds broken;
Parent strand acts as a template / copied / semi-conservative replication;
Nucleotides line up by complementary base pairing; (Adenine & Thymine etc)
Role of DNA polymerase: joins adjacent nucleotides on the developing strand via condensation and formation of phosphodiester bond;
5’ to 3’ direction
Each new DNA molecule has 1 template and 1 new strand
Formed by semi-conservative replication.
Why is the DNA heat to 95°C during PCR?
Produce single stranded DNA
Breaks WEAK hydrogen bonds between strands
Why do you add primers during PCR?
Attaches to / complementary to start of the gene / end of fragment;
Replication of base sequence from here;
Prevents strands annealing
Explain why ‘base-pairs’ is a suitable unit for measuring the length of a piece of DNA
DNA = 2 chains / joined by linking of 2 bases / A with T and G with C/ purine pairs with pyrimidine;
Bases are a constant distance apart / nucleotides occupy constant distance/
each base-pair is same length / sugar-phosphate is a constant distance;
Name one mutagenic agent
high energy radiation /ionising particles e.g. named particles/α, β, γ & X-rays;
benzene;
x rays/cosmic rays;
uv (light);
A deletion mutation occurs in gene 1.
Describe how a deletion mutation alters the structure of a gene.
removal of one or more bases/nucleotide;
frameshift/(from point of mutation) base sequence change;
Describe the main stages in the copying, cutting and separation of the DNA.
heat DNA to 95°C / 90°C;
strands separate;
cool so that primers bind to DNA;
add DNA polymerase/nucleotides;
use of restriction enzymes to cut DNA at specific base sequence/ breaks phosphodiester bonds
use of electric current and agar/gel;
shorter fragments move further;
Describe the polymerase chain reaction.
Heat DNA;
Breaks hydrogen bonds/separates strands;
Add primers;
Add nucleotides;
Cool;
(to allow) binding of nucleotides/primers;
DNA polymerase;
Role of (DNA) polymerase;
Repeat cycle many times;
Suggest one reason why DNA replication stops in the polymerase chain reactionafter some time
Limited number of primers/nucleotides; /
Primers / nucleotides ‘used up’.
DNA polymerase (eventually)denatures
Describe a plasmid.
circular DNA;
separate from main bacterial DNA;
contains only a few genes;
Suggest why the restriction enzyme has cut the human DNA in many places but has cut the plasmid DNA only once.
enzymes only cut DNA at specific base sequence/recognition site/specific point;
sequence of bases/recognition site/specific point (on which enzyme acts)
occurs once in plasmid and many times in human DNA;
(max 1 if no reference to base sequence or recognition site)
Describe how the bacteria containing the insulin gene are used to obtain sufficient insulin for commercial use.
use of fermenters;
provides nutrients plus suitable conditions for optimum growth/named
environmental factor;
reproduction of bacteria;
insulin accumulates and is extracted;
Explain what is meant by a vector.
Carrier;
DNA/gene; (context of foreign DNA)
Into cell/other organism/host;
Explain how modified plasmids are made by genetic engineering and how the use of markers enable bacteria containing these plasmids to be detected.
isolate TARGET gene/DNA from another organism/mRNA from
cell/organism;
using restriction endonuclease/restriction enzyme/reverse transcriptase to
get DNA;
produce sticky ends;
use DNA ligase to join TARGET 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 TARGET gene;
bacteria/colonies expressing the marker gene have the TARGET gene as well;
mRNA may be described as a polymer. Explain why.
Made up of many (similar) molecules/monomers/nucleotides/units;
