The Human Genome
Project
The Human Genome Project
The Human Genome Project (HGP) was started in 1989 and
finished in 2003. Its goals included:
Identifying positions on chromosomes of all 25-30,000 genes in
human DNA
Determine the base/nucleotide sequences of each gene
Discuss (and explain) the benefits of the Human
Genome Project:
Greater scientific understanding of gene expression,
mutation and interaction
Greater understanding of genetic control in developing
human
Better understanding and unravelling of non-coding
intron regions of DNA
Improvements in molecular medicine:
Faulty genes which cause disease can be detected before the
disease can develop
This can lead to new diagnostic tests and the possibility of genetic
counselling for individuals who are carriers of faulty genes.
Normal genes may be cloned and the products of these genes can
be used to treat disease in other individuals (e.g. insulin for
diabetics)
The new technology of gene therapy is possible because of the
Human Genome Project – it involves administration of a gene to
an individual who has a defective copy of it
Understanding of Human Evolution:
The genomes of other species can be compared
with the human genome
This will give insights into the similarities or
differences in the pathways of evolution
between humans and other species
Benefits in agriculture
Mapping the genome of agricultural animals and plants
could lead to development of more nutritious, higher
yielding, disease, pest and climate resistant organisms.
Describe and explain limitations of data obtained
from the Human Genome Project:
Knowing the base sequence of genes does not provide knowledge about the
function of the proteins produced – “DNA to RNA to Proteins” is a
simplification.
A lot of the DNA is non-coding (introns) – probably useless “junk DNA”
Knowing the entire base sequence of the human DNA does not explain all the
biochemistry and functioning of human beings
There has been criticism of the huge amounts of money being spent of the
HGP – the value of the results, compared the to same amount of money spent
on other projects, has been criticised.
Ethical Problems: The problems of who has access to information, what it can
be used for, whether or not it can be used for financial gain, or the possibility
of people being singled out with “inferior genes”, etc. is still being hotly
debated.
Assess the reasons why the Human Genome Project
could not be achieved by studying linkage maps:
Linkage maps would not be useful for the HGP as:
They reveal relative positions of genes on a chromosome, while the project
requires exact positions
Do not sequence nucleotides or bases that make up genes
Does not determine which particular chromosome a gene lies on
Cross breeding experiments used in gene mapping would be unethical to
perform on humans and take an extremely long time
Gene mapping is based on recognisable characteristics, while many genes have
subtle functions not recognisable
Linkage maps only identify coding regions (exons) and not the non-coding
introns
Outline the procedure to produce recombinant DNA:
1.
A gene is cut out of the chromosome using restriction enzymes. ‘Sticky
ends’ are formed where cuts are made.
2.
Circular DNA (plasmid) from a bacteria and cut using the same
restriction enzyme
3.
The gene is mixed with the bacteria plasmid and DNA ligase is used as a
‘glue’ to allow the gene and plasmid to recombine at matching sticky
ends
4.
Plasmids are reinserted back into bacteria by adding calcium chloride to
increase permeability of bacteria membrane
5.
Bacteria reproduces and plasmids are cloned, cloning the recombinant
genes
6.
The bacteria will also express the protein now introduced into its genome
Explain how the use of recombinant DNA technology
can identify the position of a gene on a chromosome:
1.
The position of a gene is found by creating a fluorescent probe that will
attach to it
2.
The gene of interest must be sequence, i.e. the base sequence must be
known
3.
Heat is used to separate the two DNA strands into single strands
4.
A fluorescent probe is created. This is a single strand of DNA that is made
to be complementary to the bases of the gene and it can easily be identified
5.
The single stand of the probe will recombine with the single strand of the
gene
6.
Looking under a microscope, the location of the gene can then be easily
seen