or ng entlytherolea, rev n menargetecho ogyt setrans n ton technology 3. Microar
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or ng entlytherolea, rev n menargetecho ogyt setrans n ton technology 3. Microarrays are used to determine the levels of gene expression (expression analysis). In one type of microarray, hybridization of the red (eperimental) and green (control) cDNAs is proportional to the relative amounts of mRNA in the samples. Red indicates the overexpression of a gone and green indicates under expression of a gene in the experimental cells relative the control cells, yellow indicates equal expression in the experimental and control cells, and no color indicates no expression in either experimental or control cells. In an experiment, cDNA derived from a strain ol artsbiotic resistant bacteria (experimental cells) was labeled with a red fluorescent tag and cONA derived from a a non- resistant strain of the same bacterium (control cells) was 21 labeled with a green luorescent tag. The cDNAs were mixed and hybridized to a chip containing spots of DNA from genes 1-25. The results are shown on the right 6 79 10 11 12 13 14 15 18 19 20 25 @23 resistance in this case (a) Discuss the condlusions you could make about which genes might be implicated in antlbiotic antbiotics that are less vulnerable to resistance: (b) Suggest how this information could be used to design new 4. Explain how microarrays have built on earier DNA probe technology and describe the advantages they offer in studies of gene expression: Microarrays are frequently used in diagnostic medicine to compare gene expression in cancerous and non-cancerous tissue. Suggest how this information could be used: 5. Biczone Intenational 2001-2008Explanation / Answer
3 a. Genes 2 and 24 are highly expressed and genes 4,17 and 22 are repressed in the antibiotic resistant bacteria. Any of these genes could be implicated in antibiotic resistance in the bacteria.Even the under expressed genes can be implicated in antibiotic resistance. If suppose gene 4 codes for a protein that is involved in uptake of the antibiotic into the cell, and it is underexpressed this will limit entry of the antibiotic into the cell and therefore the antibiotic will not be effectve.
b. Drugs that target a combination of the gene products would be les vulnerable to resistance. This is because the bacteria are less likely or slower to evolve against drugs that inhibit multiple targets.
4. Microarrays are based on hybridization of genes (cDNA) with particular probe DNAs spotted on the microarray. The advantage is that many thousands of genes can be studied at the same time and this is useful because many biological processes including diseases are affected by the activity of many genes rather than a single gene. Also treatment based on the results of a persons microarray data would provide information for effective peronalised drug treatments
5. The microarrays would provide information about genes that are overexpressed or repressed in cancerous cells. This can be used to identify drug targets and select the most effective drugs, or those with the fewest side effects, for individual patients. Also with the information from the microarrays new drug targets can also be identified and new drugs designed, or old drugs that can target the newly identified genes involved in cancer can be used.
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