Edexcel Biology B is very scarce when it comes to finding information on it online. I've taken it upon my self to publish my own notes to help fellow students that have a hard time understanding the subject. The information in the text book is very large and can be hard to narrow down to a particu...
Genome- The total genetic material/DNA of an organism
ii Understand how PCR can be used to amplify DNA samples, and how these samples can
be used
Traditional DNA profiling requires at least 1µ of DNA/ biological material (which is around
10,000 human cells).In a crime investigation. However there may only be a minute DNA
sample available. The PCR adapts the natural process that replicates DNA in the cell,
allowing us to produce enough DNA to sequence a genome or produce a DNA profile from
tiny traces of biological material
Biological material/DNA samples that can be used include the following: blood, semen,
saliva, urine, faeces, hair, teeth, bone, tissue and cells.
The polymerase chain reaction is a method we use to amplify DNA samples.
1. Reactants ( DNA and enzyme taq) are placed in a PCR machine
2. The mixture is then heated to 90-95℃ in which the DNA separates as hydrogen
bonds between them are broken
3. The mixture is then cooled to 50-55℃ so that the primers are able to bind to the DNA
strand
4. The mixture is then heated back to 72℃ which is the optimum temperature for the
enzyme taq DNA polymerase enzyme to build the complementary strands of DNA
● in forensic science, to identify criminals and to test paternity, using DNA profiling.
DNA profiling technique used to identify criminals and test paternity. It allows us to identify
repeating patterns in the non-coding region of DNA
1. Strands of DNA from a sample are cut into fragments using the enzyme restriction
endonuclease
2. DNA fragments are then separated using gel electrophoresis
3. During this process the DNA fragments are placed in an agarose gel medium in a
buffering solution.
4. The gel contains a dye that binds to the DNA fragments in the gel
5. The dye will floureses when under U.V light, revealing a band pattern of DNA
6. An electric current is passed through and the DNA move towards positive anode
(Phosphate on dna is negative)
7. DNA fragments move at different rates according to their size and charge
8. Once electrophoresis is complete the plate is placed under ultraviolet light, DNA
flourcess and shows up clearly so it can be identified
This is the original method of profiling which needs a large sample of DNA
, The next stage is called blotting. This is where an alkaline buffer is added to the gel along
with a nylon paper placed over it. This dry absorbent material draws the DNA fragments from
the gel to the filter leaving DNA fragments as “blots “ attached to the filter. Alkaline solution
also denatures DNA fragments so strands separate and base sequences are exposed
After blotting large amounts of gene probes are added to the filter and bind with
complementary DNA strands in a process called hybridisation. Gene probes are short DNA
sequences that are complementary to specific sequences being. Each probe is labelled with
a fluorescent molecule or radioactive isotope.
The line produced by DNA samples are then compared.
Micro satellites- has 2-6 base sequences repeated between 5-100 times
The more micro satellites used in DNA profiling the more accurate it will be
It can also be used in paternity testing to see who the father is as the mother is almost
always known. If the alleged father is the biological father each of the child's micro-satellites
would be either from the mother or the alleged father
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