09BIS1012013TransciptLect9-1

There for transcribing genes in eukaryotic cells

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Unformatted text preview: hesized by This messenger a DNA-dependent RNA polymerase (RNAP). DNA-dependent In prokaryotic cells like E. coli, there is only one type of RNAP responsible In E. there for transcribing genes. In eukaryotic cells, three RNAPs are involved in transcription: In RNAPI transcribes ribosomal or rRNA, RNAPI rRNA RNAPII transcribes mRNA and RNAPII RNAPIII transcribes transfer RNA (tRNA). RNAPIII In vivo, mRNAs are differentially degraded by ribonucleases giving each mRNAs ribonucleases type of mRNA a specific half-life. The average half-life of mRNA in E. half-life The coli, yeast, and humans are 4 minutes, 20 minutes and 10 hours, coli yeast, respectively. The transient nature of mRNA provides a mechanism for genes to be The differentially expressed or regulated. This means that a gene can be differentially regulated This turn on when needed and turned off when not needed. turn BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 6 Evidence for RNA as an Intermediate Messenger Caspersson and Brachet (1950) demonstrated that mRNA synthesis Caspersson and protein synthesis occur concomitantly in the cell. and David Prescott’’s pulse/chase experiments using 3H-cytidine and autos radiography showed that RNA was made in the nucleus and radiography transported to the cytoplasm. transported Protein synthesis can not in the absence of RNA synthesis. not RNA isolated from a particular cell can hybridize with ssDNA from that RNA cell to form a heteroduplex. heteroduplex The base composition of RNA is generally similar to the base The composition of the DNA from which it is made. from Base Composition A T or U G C E. coli DNA...
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This note was uploaded on 02/12/2014 for the course BIS 101 taught by Professor Simonchan during the Spring '08 term at UC Davis.

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