Applications of the Human Genome
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Why did people want to figure out the sequence of the human genome?
- To improve diagnosis of disease
- To help identify criminals
- To be able to better match donors and recipients in transplant situations
What type of diseases are caused by a disruption of a single gene?
Monogenetic diseases are usually either...?
- Autosomal dominant
- Autosomal recessive eg cystic fibrosis
- X linked (usually recessive) eg Duchenne Muscular Dystrophy
What type of diseases are caused by a disruption of several genes?
Cystic fibrosis is an autosomal ______ hereditary dieases of the exocrine glands?
What is cystic fibrosis? Explain what happens because of the mutation
- A 'defective' gene encoding for an ion (Cl-) transport membrane protein causes it not to fold properly and therefore it doesnt work properly. This stops epithelial cells being fully hydrated.
- This causes sticky mucus in the lungs making it difficult to breathe and fight infection in the lungs. CF patients also have salty sweat.
What does Duchenne Muscular Dystophy cause?
Rapidly progressive muscle weakness
Does DMD mostly affect boys or girls? Why?
It usually affects boys as it is caused by an X-linked recessive allele
How do you find out which gene alteration causes a condition?
The defect is first mapped onto a chromosomal region by looking for genetic markers that are co-inherited with the disease. When the chromosomal location of the gene is established more detailed analysis takes place eg physical mapping and then sequencing of the gene.
Which technique is used to find unknown genes? How does it work?
- Chromosome walking
- A known linked gene or marker that is commonly inherited with the gene in question is sequenced and primers are made from this section. The chain is then replicated and elongated. This chain is then sequenced, a new primer made and the process is repeated until the gene is sequenced.
Genes can be made deficient by either having nucleotide bases...?
- Introduced (substitution)
- Delelted (deletion)
- Inserted (insertion)
Gene mutations can affect how the end protein ______ and therefore hwo well it functions?
Who might be screened for a genetic condition?
- People with a history of disease in a family
- Older mothers
What is the difference between a single-locus probe and a multi-locus probe?
A single-locus probe have a complementary sequence at only one location within the genome being probed whereas multi-locus probes have a complementary sequence at many locations within the genome being probed
What are the three ways to scan for genetic conditions?
- Chromosome can be removed directly from the cell, treated (to seperate the DNA) and then probed with a gene sequence that will anneal to a defective gene.
- DNA can be extracted. PCR is used to amplify the gene of interest. The results are run on a gel and the size of the band is analysed.
- The gene could be sequenced and compared against a 'normal' gene to see if there are any differences in the nucletide sequence
What is a hybridisation probe?
- A hybridisation probe is a short piece of DNA that is denatured (by heating) into single strands and then labelled, usually with radioactive phosphorus.
- This creates a short piece of radioactively labelled DNA with known sequence that will anneal with the complementary nucleic acid strands in the DNa under test. If the probe complements the defedtive genetic code it will bind to it during hybridisation.
What is genetic conselling?
The process by which patients or relatives at risk of an inherited disorder are advised of the consequences and nature of the disorder, the probability of developing or transmitting it and the options open to them
What is the aim of genetic conselling?
The aim is not to make decisions for people but to enable them to have the necessary understanding of the situation so that they can decide for themselves
What process involves the addition of a healthy, working copy of the faulty gene into the appropriate cells of the body?
What are the two most common ways used to transfer genes into cells?
- Viruses eg the adenovirus is commonly used in gene therapy
- Liposomes - fatty substances that naturally adhere to the surface of cells
Viruses and liposomes are known as what?
Gene transfer agents
What are some challenges with gene therapy?
- Getting the gene into the cells more efficiently
- To make gene expression last longer
- Viruses are unpredictable (can mutate). Possibility of complex side effects eg virus could intergrate into host DNA and cause mutations/cancer
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