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Genomes & their evolution

Genomes & their evolution. Ch 21.4,5. 21.4 – Multicellular eukaryotes have much noncoding DNA & many multigene families. About 1.2% of the human genome is protein coding exons.

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Genomes & their evolution

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  1. Genomes & their evolution Ch 21.4,5

  2. 21.4 – Multicellular eukaryotes have much noncoding DNA & many multigene families About 1.2% of the human genome is protein coding exons. In 9/2012, in papers in Nature, the ENCODE group has produced a stunning inventory of previously hidden switches, signals and sign posts embedded like runes throughout the entire length of human DNA.

  3. DNA sequences – non coding • Regulatory sequences • Repetitive DNA sequences • Tandem repeats • Interspersed repeats

  4. Transposable elements • Segments of DNA that can move from one place to another within an organism’s genome • Movement is by a form of recombination

  5. Transposons & Retrotransposons

  6. Retrotransposons – 40% of human genome • DNA Transposons – 3% of human genome Both require transcription to work - can interrupt gene function - can introduce genetic variation, through rearrangment

  7. Alu elements • Transposable elements – family of related sequences • About 10% of human genome • 300 nt long, do not code for any proteins

  8. Other repetitive DNA • Simple sequence DNA – many copies of short tandem repeated sequences • STR – short tandem repeat – 3% of human genome

  9. Multigene families • Many genes occur in multigene families- collections of identical or very similar genes • Allow for many copies of the mRNA and protein • i.e. family for rRNA molecules – identical genes - rRNA is final product • i.e. globin families – non identical genes – produce proteins found in polypeptide subunits in hemoglobin.

  10. 21.5 Duplication, rearrangement & mutation contribute to genome evolution • Errors in Meiosis and duplication of genes • Nondisjunction can result in polyploidy

  11. Human & mouse chromosomes

  12. Unequal crossing over can lead to duplication of genes • Transposons are homologous in chromosomes, can get duplicated

  13. Transposons and evolution • 3 ways Transposons may have contributed to the evolution of the genome • Promote recombination between different chromosomes • Disrupt genes or control elements • Carry genes or individual exons to new locations • http://www.youtube.com/watch?v=9MPiRx3SPMM

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