Tuesday 1 November 2011

DNA profiling


DNA profiling
      DNA profiling involves the partial sequencing of genomes
  • ·       Profiles tend to focus on areas of satellite of junk DNA which vary significantly between individuals (e.g. the repeated sequence of 16 base pairs on the short arm of chromosome 1)
  • ·       By sequencing a number of sections a unique genetic fingerprint can be created for an individual.
  • ·       Used for: paternity tests and criminal investigations
  • ·       By obtaining DNA profiles from the child, mother and potential fathers, paternity can be established.


Gel electrophoresis
  • ·       The laboratory technique separates fragments of DNA to identify its origin.
  • ·       Restriction enzymes are used to cut the long filaments of DNA into different sized fragments.
  • ·       The DNA fragments are placed into small wells in the gel which are aligned along one end.
  • ·       The gel is exposed to an electric current that is positive on one side and negative on the other.
  • ·       The effect is that the biggest, heaviest and least charged particles do not move easily through the gel so they get stuck very close to the wells they were in at the origin.
  • ·       The smallest and most charged particles pass through the gel to the other side with least difficulty.
  • ·       Medium sized particles are distributed in between.
  • ·       In the end the fragments leave behind a banded pattern of DNA.


Outline the process of DNA profiling (genetic fingerprinting), including ways in which it can be used (6)

  • DNA profiling is often used for criminal investigations or for paternity tests. Firstly, a sample of DNA (often satellite DNA) is required through either hair or from a sample of saliva. The Polymerase chain reaction (PCR) amplifies the DNA and it is an automated process that can produce sufficient DNA in 20 cycles. The DNA is cut using restriction enzymes and these fragments are separated in a process known as electrophoresis. By sequencing a number of sections a unique ‘genetic fingerprint’ can be created for an individual.


2a.
i)  Both the males and females are affected so it’s not sex linked.

ii) It’s likely to be dominant because most of the parents seem to have these symptoms of LDL cholesterol concentration in the blood.

b. III-I= fhfh and III-2 FHfh
ii) 50%

c) a high chance

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