GeneRegulation160-page9 - which a gene or portion of...

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Gene Regulation - 9 Transcription Factor Binding Sites Transcription factor proteins have specific binding sites that fit into the DNA molecule at the appropriate location. As expected, the binding sites have specific structural elements, called motifs or domains, each of which is cleverly named. One of the more common binding motifs is the helix-turn-helix motif, a protein helix with a bend in it. Regulatory proteins generally have pairs of helix-turn-helix motifs for more strength. Often, repressor molecules attach to the binding motif, changing its shape so it can attach to the DNA molecule repressing its access to RNA polymerase. Helix-Turn-Helix on DNA Tryptophan binding motif of paired helix-turn-helix Examples of Transcription Controls in Eukaryotes Gene Amplification It is possible to get multiple copies of genes via gene amplification, a process in
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Unformatted text preview: which a gene, or portion of chromosome, or even entire chromosomes get multiplied many, many times. Salivary glands of many flies have gene amplification of chromosomes forming polytene chromosomes, which associated puffs. Fruit Fly Polytene Chromosome Gene amplification occurs in ovum cells of vertebrates when the genes for ribosomal RNA (rRNA) get replicated millions of times to ensure that the cytoplasm will have the many, many ribosomes needed for protein synthesis activities in early development. Cancer cells can also have gene amplification, where genes with resistance to the chemotherapy drugs are replicated thousands of times. Increasing the drug concentration results in increasing the resistance of the cancer cell population to the drug by selecting for those cells that have amplified genes for drug resistance....
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