Biochemistry

Running head: BIOCHEMISTRY
BIOCHEMISTRY
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1BIOCHEMISTRY
The Human Genome Project involves the sequencing of all the DNA in a human cell.
All of the human cells which have a nucleus isolated from a particular individual, contains all
the information that is required to build up that particular individual. There are about 31,000
genes present in a human. The human genome is build-up of 3.2x 109 bases. Among them
only 1.1% of the proteins are involved in protein encoding. 28% of the genome is transcribed
to mRNA so only 5% of this is exons. The rest of the component is the introns which are
basically the meaningless sequences like the lysozyme enzyme gene that is 60kb but only
500b code the amino acid sequence. It is perceived that 50-60% single copy DNA sequences
includes most gene among which 25-40% are moderately repeated DNA. It is also seen that
10-15% simple sequence DNA (5-10bp) repeated in long arrays. During meiosis crossover
occurs in these regions.
The gene location on the chromosomes is shown by the BRCA2 gene which is the
breast cancer 2 early onset. It plays a role in DNA repair where the mutation increases risk of
breast, ovarian and prostate cancer. The cytogenic location is 13q12.3 where q=long arm of
chromosome - 12.3 – banding pattern and the Molecular Location on chromosome 13: base
pairs 32,314,861 to 32,399,849.
The significance of the genome sequencing shows an improved method of diagnosis
of the disease. This method allows the early detection of the genetic predispositions.
Additionally plays a role in gene therapy where the faulty genes can be replaced. This also
has a role in pharmacogenetics where the drug metabolism occurs by enzymes which vary
genetically between individuals. The drug blood concentration is too low for ineffective
treatment and is too high for the side effects.
Pharmacokinetics also involve single nucleotide polymorphism which is the most
common source of genetic variation, where there is replacement of the single nucleotide like

2BIOCHEMISTRY
for example C or T. SNP generally occurs between the genes however it can also occur in the
promotor or the structural part of the gene. The SNPs in genes that are coding for drug
metabolising enzymes can affect metabolism of specific drugs. Additionally could produce
different amount of enzyme or less efficient enzyme.
The BMA was able to identify a wide range situations where a disorder needs to be
tested. For the analysis of a specific gene, the product or the function or other DNA or
chromosome analysis, to detect or exclude an alteration likely to be associated with a genetic
disorder. This is of two types, where there is a predictive type and a diagnostic type. In the
predictive type there are no symptoms however in the diagnostic type there is a symptom of a
disorder.
The predictive tests involves the pre-symptomatic and pre-disposal tests like for
example Huntington ’s disease and BRCA 1 &2 increase risk of breast cancer respectively.
There are certain drawbacks like potential life insurance issues, lack of understanding of
genetics by layperson along with the family issues. There is also antenatal screening which is
carried out on all women.
The metabolic rate refers to the total energy produced and used by the body per unit
time. This metabolic energy is used for Basal metabolism, thermal effect of food-energy cost
of gut motility and digestive processes and for the muscular activity. The basic terms
associated with energy metabolism includes metabolism- : total of all the chemical changes
that occur in the body, anabolism that is combining of molecules to produce larger ones, e.g.
proteins, using energy and catabolism which is the breakdown of molecules into smaller ones
producing energy to drive energetically unfavourable reactions e.g. anabolism, ion transport
across membranes, muscle fibre contraction. ATP is basic currency of energy which is