Researchers can study the function of a gene by expressing it in cells where it is not normally expressed, by overexpressing it, or by inactivating the gene in a living organism. CRISPR technology allows selective inactivation or alteration of gene sequences. Antisense RNAs and siRNAs prevent gene expression by selectively blocking mRNA translation. DNA microarrays allow the simultaneous analysis of many different mRNA transcripts.
learning outcomes
You should be able to:
Outline experiments that use RNA interference to develop new drugs for diseases.
Describe how microarrays are used to examine patterns of gene expression
In some bladder cancers, the gene for the cell signaling molecules, Ras, is mutated, resulting in an altered protein that stimulates cell division. How might siRNA technology be used to develop a drug to treat this disease? Would the drug be specific for the cancer?
Antisense RNA and siRNA act at to prevent translation by binding to mRNA by base pairing and leading to its breakdown in the cytoplasm.
As pea seeds germinate, the embryo changes which genes are expressed. How would you use microarrays to analyze this?
Germinate pea seeds and extract RNA from the embryos at different times. Make cDNA from the mRNA's and hybridize the cDNA's to a library of genes from the entire plant genome. The extent of hybridization to the genes will indicate differences in which genes are expressed.
Both antisense RNA and CRISPR technology can be used to block the expression of specific genes. What is the additional advantage of CRISPR?
CRISPR has the additional advantage of specifically changing the nucleotides in genes, that is, introducing mutations or reversions.
Now that you’ve seen how DNA can be fragmented, recombined, manipulated, and put back into living organisms, let’s see some examples of how these techniques are used to make useful products.