Chapter 14 Study Guide

Chapter 14 Study Guide - Study Guide 14 UNIT III: - Meiosis...

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Study Guide 14 UNIT III: - Meiosis (and Genetic Variation) - Mendel & the Gene (linkage and crossing over) - How Do Genes Work ( DNA = genes; the genetic code) - DNA Synthesis ... (Replication) - Transcription and Translation - Control of Gene Expression in Bacteria - Control of Gene Expression in Eukaryotes - A. Recombinant DNA and Cloning to make human insulin A grad student in California first proposed to put foreign genes into plasmids and introduce the recombinant plasmids into bacterial hosts. Once inside of bacterial cells, plasmids replicate, producing many copies of the foreign gene-containing DNA. Since bacterial cells transformed by plasmids often acquired antibiotic resistance , from genes encoded on the plasmids, it was possible to identify cells that had become transformed with plasmids from those that hadn’t. And then, the ability of complementary strands to H-bond to each other offered a way to detect the recombinant plasmids from those that were not recombinant. In a similar vein, virus DNA could be recombined with foreign DNA and used to infect cells that reproduced many copies of the foreign genes. 1. The following information was mobilized to clone a human insulin gene: . Bacteria restriction endonucleases cut DNA at specific base sequences. These sequences are protected in the bacterial DNA, but not in foreign DNA that gets in the cell by transformation or by viral infection. These enzymes destroy viral genomes, limiting viral infections. Many restriction endonucleaes leave sticky ends at their cut sites: b. Plasmids are small circular double stranded DNA molecules passed between bacteria by transformation. They vary in size and often contain genes that confer antibiotic resistance on the cells that have such plasmids: c. DNA ligase (see replication) makes phosphodiester bonds between DNA molecules, and could thus put together DNA fragments cut by the same restriction endonuclease but
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obtained from different organisms, thus recombining their DNAs: d. Retroviruses (like HIV) infect eukaryotic cells and have an RNA chromosome (genome). After infecting cells the enzyme reverse transcriptase catalyzes copy DNA ( cDNA ) synthesis using the viral RNA as a template. The new strand of DNA is then ‘copied’ by DNA polymerase to make a double-stranded viral DNA molecule that then replicates to make more viruses (see drawing at right). The action of reverse transcriptase is seen in Fig. 19.1 . These activities were exported to the test tube! e. If you could get or synthesize a pure sequence of nucleic acid, you could tag it with a radioactive marker and use it as a probe to identify its complementary sequence in a mixture of DNA ( Fig. 19.4 ). This probe would then be mixed with total DNA from an organism. If the organism had a copy of the gene for the radioactive sequence, a radioactive double strand would form and could be detected by one of several methods. 2.
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This note was uploaded on 11/22/2009 for the course BIO SCI 150 taught by Professor Geraldbergstrom during the Spring '08 term at Wisconsin Milwaukee.

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Chapter 14 Study Guide - Study Guide 14 UNIT III: - Meiosis...

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