13 Aug Most scientists who use DNA microarrays obtain them f

Most scientists who use DNA microarrays obtain them from companies that mass produce them from the government by making them in their labs by exploiting ambitious graduate students In this study, cancerous and normal skin tissue samples were excised with a scalpel. Each skin sample was then placed into a sample tube along with solvent, shaken on a vortex and centrifuged. When the sample tubes came out of the centrifuge, there was a top layer and a bottom layer. For our purposes, we went on to use ______________ for further processing.’ only the bottom layer none of the options listed a mixture of top and bottom layers only the top layer The purpose of the vortex instrument is to vigorously shake the tissue sample in the solvent so that it dissolves. spin the tissue/solvent mixture around to separate the solids cause the mRNA to bind to the pellets dispose of biohazardous waste safely ‘Once the RNA is isolated from the DNA, proteins and other materials, the solvent/RNA mixture is run through a column of all beads. Each bead has several short strands of polyT RNA sticking out of it. In this step:’ ‘mRNA sticks to the beads, while rRNA and tRNA run right through the column’ ‘rRNA and tRNA stick to the beads, while mRNA runs right through the column’ none of the options listed ‘tRNA sticks to the beads, while mRNA and rRNA run right through the column’ ‘Once the mRNA is isolated, you make a DNA copy of it using by adding polyT primers, labeled DNA nucleotides, and an enzyme known as:’ reverse transcriptase tyrosine hydroxylase alcohol dehydrogenase ATP kinase A DNA copy of a mRNA transcript is known as copied DNA (abbreviated cDNA) complementary DNA (abbreviated cDNA) recombinant DNA (abbreviated rDNA) mitochondrial DNA (abbreviated mtDNA) Each spot on the DNA microarray in embedded with copies of DNA from one particular gene copies of DNA from several different genes with similar functions copies of DNA from several different genes with different functions copies of mRNA from one or more genes ‘When we say that the cDNA derived from our sample has hybridized to a particular spot on the array, we mean that: ‘ The cDNA from the sample has stuck to the DNA on the microarray at that point. The cDNA from the sample is jumbled and cannot be trusted. You need to buy microarrays from different manufacturers and triangulate the results The cDNA has been used to make an mRNA copy ‘In this particular experiment, we used red-labeled DNA to process the sample from _____________ tissue and the green-labeled DNA to process the sample from ___________. ‘ cancerous; normal normal; cancerous normal; normal cancerous; cancerous After scanning the green labeled areas and the red labeled areas, when we combine the two images, the spots that show up as yellow correspond to ‘ genes that were not expressed at all in either normal or cancerous skin cells genes expressed by both normal or cancerous skin cells. ‘genes expressed by cancerous, but not normal skin cells’ ‘genes expressed by normal, but not cancer skin cells. ‘ ‘In interpreting the results of this study, spots on the microarray that are red correspond to:’ genes that are turned up by cancer genes that are turned down by cancer genes that are unaffected by cancer genes that aren t expressed in normal or cancerous cells ‘In interpreting the results of this study, spots on the the microarray that are green correspond to genes that are ‘ genes that are unaffected by cancer genes that aren t expressed in normal or cancerous cells genes that are turned down by cancer genes that are turned up by cancer ‘When the DNA microarray study tells us that a large number of genes have been turned up (or turned down) by a disorder, the most likely explanation is that ‘ the turned up genes are likely controlled by a gene that has gone bad all of these genes are genes that have gone bad themselves even just one mutation in any of these affected genes would have been sufficient to cause the disorder the cytoplasm has too many free radicals in it A gene shown by the microarray to be expressed is : definitely making protein ‘probably making protein, but a protein expression analysis would be needed to know for sure’ probably making protein but there’s no way to know for sure definitely not making protein In the application of this technique to skin cancer, a gene that has gone bad ‘ ‘may or may not be identified at all, but the overall pattern of results can give important clues’ can almost always be identified via DNA microarray