Lecture 3 Eukaryote Sequence Organisation.docx

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Biological Sciences
Craig Miller

Lecture 3 Eukaryote Sequence Organisation Tuesday, 23 July 2013 11:42 a.m. Eukaryotic genome:  50% is repeated sequences, within that are transposable elements that move around the genome resulting in most mutations.  Is larger than prokaryotes, vary by ~5000 fold between the largest and the smallest. No relationship between genome size and phenotypic complexity. Humans have one of the smallest number of genes per genome, haploid genome is 3200 mbp.  Number of genes:  Prokaryotes have 1500-7500 genes per a genome while eukaryotes have 5000-40000 genes.  In eukaryotes the number of genes in a species is lower than expected when compared to size of genome.  93% of human genes can be spliced multiple ways with multiple exons.  No relationship between complexity and number of genes.  Prokayotes have highly condensed genomes while eukaryotes have largely uncondensed genomes. Gene density:  Humans have 7 genes per a ? Which is the lowest density known. Vast majority is non coding. Functional genes - single copy:  Encode proteins, make up 1.5% of genome. Contains exons which are variable in size.  Gene regulatory sequences account for 20% of genome and introns account for 5%.  Remainder 15% is unique non coding DNA and spacer sequences. Dispersed gene families:  Most arise through gene duplication of existing genes and are spread throughout the genome but may dispersed along the same chromosome with spacer sequences.  Several types of proteins are encoded by families of homologous genes spread throughout the genome eg globin genes.  Some genes may be non functioning - pseudogenes Tandemly repeated arrays:  Next to each other, often proteins that are required in large amounts such as histone proteins and rRNA which are in the NO. Consist of identical DNA sequences, in the NO there are 250 copies of the tandemly repeated spacer region and transcriptional unit. Non coding functional sequenc
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