Human Genome and Genome Structure!Take home points!Complexity isn't defined by its genome size or the number of genes!•Much complexity is added by mechanisms at other levels (transcription, RNA processing, •translation)!Our genome= many diff. genetic elements, only a small part codes for protein sequences!•Extrachromosomal elements can affect human cellular functions: mitochrondria, viruses, bacteria •(plasmids)!!Objectives!1) Basic features of DNA!2) Genome complexity!3) Nuclear and organelle genomes!4) Med relevance!!1)!DNA-> RNA-> polypeptide-> mature protein!•Sugar-phosphate backbone w/nitrogenous base, bases face each other!•5' to 3' orientation!•Double helix, anti-parallel!•A=T, CIIIG (triple bond), more stable!•B form, right-handed most common. Other forms, Z and L-handed (Supercoiling). !•DNA supercoils, to unwind/relax it, we have topoisomerases to cut and reanneal!•Two main types: I cuts 1 strand and II cuts 2 strands!◦Tops= drug targets (antibiotics and chemo)!◦!2) !DNA-> nucleosome-> beads on a string-> 30nm fiber->active chromosome-> metaphase •chromosome!Human genome: 22 autosome pairs+ 2 sex chromosomes = 46 overall chromosomes!•Tendency for complexity to increase and genome size increases, but this isn't true all the time, and •the size of the genome doesn't determine complexity (ex. lily genome > human genome)!Number of genes varies a lot among/in species!•Reason we are so complex, but have fewer genes than some less complex? We do so much •processing/regulation! One gene can lead to many different gene products due to!Transcriptional regulation: how much/at all a certain gene is transcribed!◦RNA processing: does it get translated? does it reg. effeciency? introns getting cut out...!◦Translational regulation!◦Post-translational regulation: what we put on proteins (ex. phosphorylate them)!◦AKA one gene can lead to many different gene products! !◦Our genome is about 20,000 genes!•Only 1% of our genome encodes proteins!•45% was/is a mobile genetic element!•Sines= short interspersed nuclear elements!◦Lines= long interspersed nulcear elements!◦Retroviral like elements!◦Above 3 can make copy of selves (derived from retrotransposons) and put in genes!◦DNA transposon fossils cut and paste!◦= TRANSPOSONS!◦12% tandem repeats (aka satellite DNA)!•Simple seq. DNA!◦TTAGGG 100s of times!◦Often at centromeres and telomeres, mostly junk DNA!◦!3)!Mitochrondria!•Inherited maternally!◦17,000 bp, 37 genes (protein, tRNA, mitoch. ribosome)!◦Pretty much all systems can be affected in mitochrondrial disorders!◦Viruses!•DNA or RNA, huge range in size (3000-1.2 billion bp)!◦Can replicate only in host, so most don't kill it!!◦Source of some jumping genes (transposons)!◦Plasmids!•Mostly proks, some lower euks!◦Non-essential genes!◦R factors, antibiotic resistance (via conjugation= when an R factor is transferred from one ◦bacteria cell to another)= HORIZONTAL GENE TRANSFER!2 other HGTs!◦Transformation- take up DNA from envi!‣Transduction- virus med. exchange of genetic material between bacterial cells!‣!4)!Genome -> genetic diseases!•Differential susceptibility
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