TAGGGCOAATICGAGCTCGGTACCCOGNGGA GAS Tissue-Specific Gene Expression In this chapter, we discussed how gene expression ca

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Tagggcoaaticgagctcggtacccogngga Gas Tissue Specific Gene Expression In This Chapter We Discussed How Gene Expression Ca 1 (99.58 KiB) Viewed 14 times

TAGGGCOAATICGAGCTCGGTACCCOGNGGA GAS Tissue-Specific Gene Expression In this chapter, we discussed how gene expression can be regulated in complex ways. One aspect of regulation we considered is the way pro- moter, enhancer, and silencer sequences can govern transcriptional initiation of genes to allow for tissue-specific gene expression. All cells and tissues of an organism possess the same genome (with some genomic variation as you will leam in Chapter 21), and many genes are expressed in all cell and tissue types. However, muscle cells, blood cells, and all other tissue types express genes that are largely tissue specific (i.e., they have limited or no expression in other tissue types). In this exercise, we return to the National Center for Biotechnology Infor mation (NCBI) site and use the search tool BLAST (Basic Local Alignment Search Tool), which you were introduced to in an earlier "Exploring Genomics" exercise (see Chapter 10). We will use BLAST to learn more about tissue-specific gene-expression patterns. > Continued: the gene name or the gene name itself in order to retrieve a UniGene report. Be sure to explore the "EST Profile" link under the "Gene Expression" category in each UniGene report. EST profiles will show a table of gene-expression patterns in different tissues. Also explore the "GEO Profiles" link under the "Gene Expression" category of the UniGene reports, when available. EXPLORING GENOMICS Exercise-Tissue-Specific Expression 1. Access BLAST from the NCBI Web site at https://blast.ncbi.nlm.nih.gov /Blast.cgi NM 021588.1 NM_00739.1 AY260853.1 NM_004917 Gene 2. The following are GenBank accession numbers for four different genes that show tissue-specific expression pat- terns. You will perform your searches on these genes. 3. For each gene, carry out a nucleotide BLAST search using the accession numbers for your sequence query. (Refer to the "Exploring Genomics" feature in Chapter 10 if you need to refresh your memory on BLAST searches.) Because the accession num- bers are for nucleotide sequences, be sure to use the "Nucleotide BLAST" These links will take you to a number of gene-expression studies related to each gene of interest. Explore these resources for each gene, and then answer the fol- lowing questions: a. What is the identity of each sequence, based on sequence align- ment? How do you know this? SASTA b. What species was each gene cloned from? Mastering Genetics Visit the Study Area: Exploring Genomics program when running your searches. Once you enter "Nucleotide BLAST," under the "Choose Search Set" cat- egory, make sure the database is set to "Others (nr, etc.)," so that you are not searching an organism-specific database. 4. Once your BLAST search results appear, look at the top alignment for each gene. Clicking on the link for the top alignment will take you to the. page showing the sequence alignment for this gene. To the far right of the page, if you scroll down you will see a section called "Related Information." The "Gene" link provides a report on details related to this gene. Some alignments will display a link for "Map Viewer," which will take you to genome mapping information about the gene. The "UniGene" link will show you a UniGene report. For some genes, upon entering UniGene you may need to click a link above. c. Which tissue(s) are known to express each gene? d. Does this gene show regulated expression during different times of development? e. Which gene shows the most restricted pattern of expression by being expressed in the fewest tissues?