MIT 7 03 - EUKARYOTIC GENES AND GENOMES II (6 pages)

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EUKARYOTIC GENES AND GENOMES II



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EUKARYOTIC GENES AND GENOMES II

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Lecture Notes


Pages:
6
School:
Massachusetts Institute of Technology
Course:
7 03 - Genetics
Genetics Documents

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1 Fall 2006 7 03 7 03 2006 LECTURE 21 EUKARYOTIC GENES AND GENOMES II In the last lecture we considered the structure of genes in eukaryotic organisms and went on to figure out a way to identify S cerevisiae genes that are transcriptionally regulated in response to a change in environment The ability to regulate gene expression in response to environmental cues is a fundamental requirement for all living cells both prokaryote and eukaryote We considered how many genes each organism has about 4 000 for E coli 6 000 for yeast and a little over 20 000 for mouse and humans But only a subset of these genes is actually expressed at any one time in any particular cell For multicellular organisms this becomes even more apparent it is obvious that skin cells must be expressing a different set of genes than liver cells although of course there must be a common set of genes that are expressed in both cell types these are often called housekeeping genes There are a number of ways that gene regulation in eukaryotes differs from gene regulation in prokaryotes Eukaryotic genes are not organized into operons Eukaryotic regulatory genes are not usually linked to the genes they regulate Some of the regulatory proteins must ultimately be compartmentalized to the nucleus even when signaling begins at the cell membrane or in the cytoplasm Eukaryotic DNA is wrapped around nucleosomes Today we will consider how one can use genetics to begin to dissect the mechanisms by which gene transcription can be regulated For this we will take the example of the yeast GAL genes in S cerevisiae GALACTOSE METABOLISM IN YEAST Reaction Enzyme Gene Galactokinase GAL1 Galactose transferase GAL7 Galactose epimerase GAL10 D galactose D galactose 1 phosphate UDP D galactose UDP D glucose D glucose 1 phosphate G 1 en oded UDP glucose Phosphorylase Phosphoglucomutase D glucose 6 phosphate GLYCOLYSIS G 1 G G 10 trans ription all indu ed in the presen e of glu ose9 o is this a hie ed9 2 Fall 2006 7 03 Once a gene



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