BIOLOGY
Human genome tasks
Genome Tasks
The Human Genome Project
The Human Genome Project set out to sequence the nucleotides in the human genome and began in 1990. By the year 2000 enough advances in DNA sequencing and in computing had occurred to allow a working draft to be published which was followed by a more complete draft of the 3 billion base pairs 3 years later.
The human genome project was designed to improve knowledge and understanding of genetic disorders and consequently improve their diagnosis and treatment.
Despite rapid advances in DNA sequencing it still took over 10 years to sequence the 20,500 genes in the whole human genome.
What method was initially used to sequence the DNA? Suggest why this method resulted in the time taken to complete the whole genome?
The 100,000 Genome Project
The 100,000 Genome Project carried out by genomics England under the Department of health follows on from the successful human genome project. It will use NGS to sequence 100,000 genomes from NHS patients with cancer or a rare disease and from members of their families.
It aims to create an ethical, transparent programme based on consent to set up a genomics service for the NHS to benefit patients, this will enable medical and scientific discoveries in a developing uk genomics industry.
It is thought that by using sequenced data along with medical records, the cause of diseases will be identified and understood and their diagnosis and treatment improved.
The text states that The 100,000 Genome Project will use NGS. This means a genome can be sequenced in a few hours.
Next Generation Sequencing
One of the aims of the project is to ensure that it is ethical. Choose the words from the menu which are synonyms of the term ethical.
Discuss – The outcome of The 100,000 Genome Project could lead to totally individualised health care. How might this work?
Moral and ethical concerns
A vast quantity of data will be produced by The 100,000 Genome Project. The potential for which is extensive. We don’t yet know how this information may be used in the future.
It is a societal issue to decide where the legal and moral responsibilities for it will lie. It is not known who will own the information found in a person’s genetic code once it has been sequenced and there are as many ways this information may be misused as there are used to benefit the patient.
From the list below, select which of the uses of a genetic code could be deemed ‘misuse’ of the data.
Genetic screening
One disease that can be screened for is cystic fibrosis. Cystic fibrosis is a mutation of the CFTR gene (Cystic fibrosis Transmembrane Conductance Regulator)
The CFTR protein functions as a channel for the movement of chloride ions in and out of cells, the non-functioning of this protein means a lack of chloride ions inside the membrane of passages in the lungs and pancreas. Less osmosis occurs and and so less water is present to dilute mucus in passageways which becomes thick and sticky. The most common mutation of the CFTR gene occurs in position 508 of the nucleotide sequence. The bases on the coding strand at position 507 are:
which is a template for the mRNA codon AUC. At position 508 the base code is:
which has a corresponding mRNA sequence of UUU. So together that section of mRNA reads:
These codons code for the amino acids isoleucine and phenylalanine respectively.
The most common DNA mutation is a deletion of the cytosine base at position 507 and two Thymine bases at position 508.
What is the original DNA code from which the mRNA template is made?
TAGAAA
One of the most common mutations in cystic fibrosis is the deletion of the DNA bases
What will the remaining mRNA sequence be?
AUU
Genetic Testing
The method of genetic testing is usually performed using a sample of blood, hair, skin or amniotic fluid. Possibly the use of a buccal smear is used which uses a small brush or cotton swab to collect a sample of cells from the inside surface of the cheek.
The sample is sent to a laboratory and specific mutations in DNA are checked for. The results of these tests are given to a doctor or genetic counsellor to discuss with the patient. A councellor is there to make sure the person understands the procedure, the benefits and limitations of the test and possible consequences of the result.
Which of the diseases listed here could be detected using this procedure to find a precise mutation in a gene?
Designer babies
Screening embryos for genetic diseases has opened a discussion on the potential for choosing embryos so that children can possess certain characteristics such as sporting ability, specific appearances, intelligence etc. These characteristics are however, not found at a single gene locus but are rather the result of many interacting genes, the environment and epigenetic modifications.
Epigenetics is an area into which much research has been done recently. It is a study not into changes in DNA but how DNA is read and these changes can be passed on through generations.
Epigenetics is the study of:
changes in gene:
Epigenetics is the study of Heritable changes in gene Expression
Impact of Genetic Testing
An outreach community and hospital testing programme in Sardinia started voluntary pre-natal or antenatal testing in 1975. Posters, information booklets and mass media helped spread the word and counselling was provided to carriers and carrier couples.
Describe the effect the introduction of genetic testing had on the incidence of B thalassaemia. Refer to the graph above.
Which of these terms can be used to describe the disease B thalassaemia in Sardinia?
endemic
With 27,500 births per year in Sardinia the incidence of disease reduced to 1/4000 after the screening programme began. What was the incidence of the disease in 1975?
27500 / 110 = 1/250