#biostripsmedia# #pratheeshpallath#
In this session Bio Strips Media takes through the important
topics of Molecular Basis of Inheritance. It is one of the most important and
scoring topics in Plus Two Biology Exam and NEET Exam.
This lecture covers:
·
Human genome project
·
Advantages
·
Methodologies
·
Salient features
·
Goals
HUMAN GENOME PROJECT (HGP)
·
Human genome
project was a 13 year project that was launched in the year 1990 and completed
in 2003.
·
This project
was coordinated by the US Department of Energy and the National Institute of
Health.
·
During the
early years the project, the Wellcome Trust (UK) became a major partner, other
countries like Japan, Germany, China and France contributed significantly.
·
Its aim was
to find out the complete DNA sequences of the human genome.
·
The two
factors that made this possible are:
·
Genetic
engineering techniques, with which it was possible to isolate and clone any
segment of DNA.
·
Availability
of simple and fast techniques, for determining the DNA sequences.
·
HGP was
called a mega project for the following facts:
·
The human
genome has approximately 3.3 x 109bp, if the cost of sequencing is
US $ 3 per bp, the approximate cost is about US $ 9 billion.
·
If the
sequences obtained were to be stored in typed form in books and if each page
contained 1000 letters and each book contained 1000 pages, then 3300 such books
would be needed to store the complete information.
·
The enormous
quantity of data expected to be generated also necessitates the use of high
speed computational devices for data storage, retrieval and analysis.
·
The project
was closely associated with a new branch of biology called Bioinformatics.
GOALS OF HGP
·
Identify all
the genes (approximately 20000-25000) in human DNA.
·
Determine the
sequences of the three billion base pairs present in human DNA.
·
Store this
information in databases.
·
Improve the
tools for data analysis.
·
Transfer the
technologies to other sectors.
·
Address the
ethical, legal and social issues that may arise from this project.
ADVANTAGES OF HGP
·
Knowledge of
the effects of variations of DNA among individuals can revolutionise the ways
to diagnose, treat and even prevent a number of diseases.
·
It provides
the clues to the understanding of human biology.
METHODOLOGIES OF HGP
·
The methods
involved two major approaches:
·
One approach
called as Expressed Sequence Tags (ESTs), focused on identifying all the genes
that expressed as RNA.
·
Second
approach called as Sequence Annotation, was to simply sequence the whole set of
genome that included all the coding and non-coding sequences and later
assigning functions to different regions in the sequence.
·
The total DNA
from the cell is isolated and converted into random fragments of relatively
smaller sizes.
·
These
fragments are then cloned in suitable hosts using specialized vectors, the
commonly used hosts are bacteria and yeast and the vectors are Bacterial
Artificial Chromosomes (BAC) and Yeast Artificial Chromosomes (YAC).
·
The fragments
are then sequenced using automated DNA sequences, which work on the principle
developed by Frederick Sanger.
·
The sequences
were then arranged on the basis of certain overlapping regions present in them.
·
Specialized
computer based programmes were developed for alignment of the sequences.
·
These
sequences were annotated and assigned to the respective chromosomes.
·
The next ask
was to assign the genetic and physical maps on the genome, this was generated
using the information on polymorphism of restriction endonuclease recognition
sites and certain repetitive DNA sequences called microsatellites.
SALIENT FEATURES OF HUMAN GENOME
·
The human
genome contains 3164.7 million nucleotides.
·
The size of
the gene varies; an average gene consists of 3000 bases, while the largest
gene, dystrophin consists of 2.4 million bases.
·
The total
number of genes is estimated at 30000 and 99.9% of the nucleotides are the same
in all humans.
·
The functions
of over 50% of the discovered genes are not known.
·
Only less
than 2% of the genome codes for proteins.
·
Repetitive
sequences make up a large portion of the human genome.
·
Chromosome
No. 1 has 2968 genes (the maximum) and the Y chromosome has 231 genes (the
least).
·
Scientists
have identified about 1.4 million locations, where DNA differs in single base
in human beings; these are called single nucleotide polymorphisms.
APPLICATIONS or FUTURE CHALLENGES OF HGP
·
Having the
complete sequence of human genome will enable a radically new approach to
biological research.
·
All the genes
in a genome or all the transcripts in a particular tissue/organ/tumor can be
studied.
·
It will be
possible to understand how the enormous number of genes and proteins work
together in interconnected networks in the chemistry of life.
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