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Summary A level Biology B Edexcel: Topic 7

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I remember writing these notes in Y12, I know first hand the amount of time that has to be invested into this subject and how difficult it can be to identify the key information. These notes are time savers, giving you more time to practice questions and past papers. The notes used for all my A-level exams, they were written in iPad therefore are electronic. Handwriting is perfect, format is kept constant. Notes have been taken directly from the book, all key information is displayed in a clear format. Same subheadings, same titles, same information, but made easier. I have used this notes and obtained an overall Y12 grade of A* and A* predicted for my final A-levels.

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DNA profiling

Introns and satellites

bypatterns in their DNA Thisprocess is
You can identityindividuals and species known as DNAprofilin
90 A PNA is made upoe introns repetitivecodingregionsbetweenthe genes Theyareinheritedinthesam
as activegenes and they are the areas involved in DNA profiling
way
Within the introns there are short sequences of DNA that are repeatedmany timesformingmicro
satellites and mini satellites The same satellites appearin the same position on each pai
Of homologous chromosomes
yet the number oe repeats of these willvaryas different
patterns are inherited from mother and father
The more closely related two individualsare the more likelysimilarities will beapparentin theirDN


How is a DNA profileproduced
Strands o DNA can be outusingenzymes restrictionendonucleases These
cut the DNA at particularpoints Different restrictionenzymes cut the
DNA at dice rent specific base sequences recognition sites giving a
mixture of dice rent sized DNA fragments made up oe mini and
microsatellites
el electrophoresis DNA eragements are placedin wells withagarosegel
to maintain the pH with known DNA fragments to aid identification
Gel contains a dye that bindsto the Dun and allows it to be seen under
UV light
raysvisibledyeis alsoadded not binds to allow it to goslightly
Faster than the DNA allowing to stop before DNA runs of the end
Electric current is passed throughthe apparatus DNAfragments move
towards the positive anode because of the negativecharge oe the
phosphate in the backbone DNAfragments move at dice rentspeeds
depending on their size UU shortwave light is clashed and the Dun Eluoresces becauseof
dye and patterns can be identified
Southern blotting and geneprobes Alkaline butter solution is added to the get after
electrophoresis Nylonpaper is placed over it this draws the solution containing the
DNA TO the Filter
Alkaline solution de natures the DNA fragments and the strands separate leaving
the bases exposed Gene probes DNAsequencesspecificto DNA fragments bind to
complementary DNA strands in the process of hybridisation DNAprofileis produced
as a graphwith each peak representing the no oe micro satellite repeats in
a fragment A singlereading means the same no oe repeats were present on both
homologous chromosomes The more micro satellites compared the more
accurate the DNA profile will be


Identifyingindividuals
The more microsatellites used to make a DNA profile the more accurate it will be
Child microsatellites come from either the mother or the father The analysis of
the childs DNA can be used to show wet her the alleged father is the biologicalparen

, DNA sequencing

The process of sequencing
DNA strands are chopped into smaller pieces
Double strands are separated and replicatedthrough PCR
Terminator bases are added to the singlestrands These are modified versions of the nucleotide
bases that when coded Eor preventany more DNA synthesis from occurring
T terminator stopsDNAsynthesis where at base would be added Each terminatorhas a
fluorescenttag in a specificcolour

tags enable the sequence of bases to be read by an
Colour automated system
Massivelyparallelsequencing involves raw data being fed into computers that compare all
DNA fragments and find areas of overlap between them


Predicting amino acid sequences
DNA sequencing can be used to determine which
protein
will be produced from a particulargene
Analysis of basepairs allows to work out which amino
acids will bejoinedtogether

Links to desease
management
DNA sequencing makes it possibleto identifyfaulty
genes see what bases have changed and understand
how these changes affect the final protein


Sequencing in action
for a heart protein causes
A mutation of a gene coding damage to the heart muscle
structure and makes the individual more likely to suffer serious heart disease The
mutation
is usually passed on as it does not manifest until an older age

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