knowledge-24 GT

• An organisms genome contains many variable number tandem repeats. Which are repeating sequences of nucleotides that appear next to each other (in tandem).
• The probability of two individuals having the same Variable number tandem repeats (VNTR) is very low. This allows genetic fingerprinting to determine genetic relationships and the genetic variability within a population using VNTRs.
• Genetic fingerprinting analyses DNA fragments that have been cloned by PCR.
• The use of genetic fingerprinting is used in the following areas:

  • forensic science- to determine if someone was present at a crime scene
  • Medical diagnosis- diagnosis of inherited disease such as Huntington's disease.
  • animal and plant breeding- to prevent unwanted inbreeding in captive breeding programs .
• Genetic fingerprinting:

  1. extraction- DNA is extracted from the sample
  2. digestion - Restriction endonucleases cut the DNA into fragments
  3. separation- Fragments are separated using gel electrophoresis.
  4. separation(cont.)- DNA fragments are transferred from the gel to nylon membrane in a process known as southern blotting.
  5. Hybridization-DNA probes are added to label the fragments.
  6. development- membrane with radioactively labelled DNA fragments is placed onto an x-ray film.
  7. development(cont.)- development of x-ray film reveals dark bands where the radioactive DNA probes have attatched.
• DNA probe-Short single stranded DNA fragments that are labelled either radioactively or fluorescently.
• Introns consists variable number tandem repeats (VNTR) which are long sequences of repeating nucleotides that do not code for anything.
• DNA probes have complementary base sequences to VNTRS (for genetic fingerprinting ) and are labelled either radioactively or fluorescently.
• DNA samples for genetic fingerprinting can be collected from ; blood , body cells , hair follicles , saliva.
• For genetic fingerprinting DNA sample is amplified using polymerase chain reaction.
• in digestion for genetic fingerprinting restriction endonuclease is complementary to VNTR's.
• For genetic fingerprinting in separation the DNA strand becomes a single strand through addition of alkaline solution.
• in genetic fingerprinting the results of hybridization are transferred to nylon sheets and then placed onto x-ray film. Agar cracks as it dries making it not suitable to hold DNA strands + probes.