Tag: molecular basis of inheritance

DNA fingerprinting is a forensic technique which identify the individuals by their DNA characteristics. A variable number tandem repeat (or VNTR) refers to presence of a short nucleotide sequence as a tandem repeat on many chromosomes; it exhibit variations in length and number of repeats between individuals. VNTR are 10-100 bp long. This DNA polymorphism is revealed during DNA finger printing in creating DNA profile of individuals. It was invented by AIec Jeffery. The first step in DNA finger printing is extraction of useable DNA followed by its digestion with restriction enzymes to produce the restriction fragments length polymorphisms, or RFLPs. The fragments are sorted according to size by gel electrophoresis. The DNA fragments are then transferred from the gel to the surface of the nylon via southern blotting. For the purpose, the agarose gel is mounted on filter-paper wick and the hybridization membrane is sandwiched between the gel and any absorbent material, which draw the transfer buffer through the gel by capillary action. The buffer flow draw the DNA molecules which are then immobilized on the synthetic membrane. Finally, radioactive probes are washed over the nylon surface to allow their joining to any DNA fragments of same composition.  A photographic film on top of the nylon surface to make a genetic fingerprint. 

DNA finger printing is a forensic technique which identifies the individuals by their DNA characteristics. A variable number tandem repeat (or VNTR) refers to the presence of a short nucleotide sequence as a tandem repeat on many chromosomes; it exhibits variations in length and number of repeats between individuals. VNTR are 10-100 bp long. This DNA polymorphism is revealed during DNA finger printing in creating DNA profile of individuals.  It was invented by AIec Jeffreys. The first step in DNA finger printing is the extraction of usable DNA followed by its digestion with restriction enzymes to produce the restriction fragments length polymorphisms or RFLPs. The fragments are then sorted according to size by gel electrophoresis. The sorted DNA fragments are then transferred from the gel to the surface of the nylon via southern blotting. For the purpose, the agarose gel is mounted on filter paper wick and the hybridization membrane is sandwiched between the gel and any absorbent material, which draw the transfer buffer through the gel by capillary action. The buffer flow draws the DNA molecules which are then immobilized on the synthetic membrane. Finally, radioactive probes are washed over the nylon surface to allow their joining to any DNA fragments of same composition. A photographic film on top of the nylon surface to make a genetic fingerprint. 

DNA fingerprinting is a test which is used to identify and evaluate the genetic information called as DNA in a person's cells. It is called as a "fingerprint" because it is very unlikely that any two people would have exactly the same DNA information, in the same way that it is very unlikely that any two people would have exactly the same physical fingerprint. The test is used to determine whether a family relationship exists between two people, to identify organisms causing a disease and to solve crimes. 

Since there are 64 triplet codons and only 20 amino acids, genetic code is non-ambiguous. Non-ambiguous code means that there is no ambiguity about a particular code. One codon specifies only one amino acid and not any other except GUG which normally codes for valine but in certain conditions it also codes for N-formyl methionine as initiation codon.

Repeated or repetitive sequences make up large portion of human genome. Repetitive sequences are nucleotide sequences that are repeated many times, sometimes hundred to thousand times. They have no direct coding function but provide information as to chromosome structure, dynamics and evolution. Approximately 1 million copies of short 5-8 base pair repeated sequences are clustered around centromeres and near the ends of chromosomes. They represent junk DNA. 

All living organisms—present, past and future are linked to one another by the sharing of the common genetic material, but to varying degrees.