E1-eukaryotic_genes

E1-eukaryotic_genes - Eukaryotic Gene Expression Regulation...

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Eukaryotic Gene Expression
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Regulation of Gene Expression in Eukaryotic Organisms How many genes are required for life? The bacteria with the simplest genome (580,000 bp) has about 470 genes. E. coli has about 4,000 genes. Yeasts have about 6,500 genes. Mammals have about 35,000 genes. Human has ~ 23,400 genes. Relationship between the size of the genome and the number of genes. Bacterial genes average about 0.8-1.0 kbp in size and occupy on average about 80% or more of the coding capacity. The gene density is similar in bacteria, those bacteria with larger genomes contain more genes. In eukaryotes, there is no correlation between the number of genes and the amount of DNA. Closely related species may have vastly different amounts of DNA. Only about 0.8-3% of the DNA encodes protein or RNA products. Genes contain introns and may extend for vast distances. Genes are frequently 5-40 kbp. The largest known gene (Dystrophin) is ~2,500 kbp in length. Some of the non-coding DNA may play a structural role. Crick has proposed that some of the non-coding DNA may represent “selfish DNA ” that is selected for in the nucleus of the cell essentially without reference to the extracellular environment.
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Lack of apparent correlation between organism and genome complexity
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Classes of DNA in a eukaryotic genome Single copy genes (1 copy/haploid) or genes with a small number of copies Highly reiterated genes (eg. Histone genes, rRNA genes) Highly repetitive DNA Moderately repetitive Variable number tandem repeats (VNTR) Short tandem repeats (STR).
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Only about 1.25% of Human DNA encodes gene products ~23,000 genes
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Short tandem repeats (STR) are the basis for human DNA forensic testing. STR are short sequences (6-20 bp) that are repeated a variable number of times (usually 5-100).
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This note was uploaded on 02/17/2012 for the course CHEM 212 taught by Professor Staff during the Fall '10 term at Rutgers.

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E1-eukaryotic_genes - Eukaryotic Gene Expression Regulation...

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