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 genomeThis 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 beingsThere 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