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Gene regulation

Gene regulation. Gene regulation. NUCLEUS. CYTOPLASM. R. S. Winning, 2003. Gene regulation. Transcription: regulated by activators (transcription factors) and repressors (rare in eukaryotes) Examples: heat shock transcription factor

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Gene regulation

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  1. Gene regulation

  2. Gene regulation NUCLEUS CYTOPLASM R. S. Winning, 2003

  3. Gene regulation Transcription:regulated by activators (transcription factors) and repressors (rare in eukaryotes) Examples: heat shock transcription factor always present; becomes active when temperature changes steroid hormones bind directly to TF to activate it peptide hormones bind to cell membrane and initiate series of reactions within the cell to activate TF

  4. Gene regulation transcription: regulated by activators (transcription factors) and repressors (rare in eukaryotes) RNA processing: different exons may be used within one gene, producing different protein products

  5. Gene regulation transcription: regulated by activators (transcription factors) and repressors (rare in eukaryotes) RNA processing: different exons may be used within one gene, producing different protein products mRNA longevity: mRNA translates as long as it is intact ‘lifespan’ encoded in the 3' UTR sequence AUUUA signals early degradation

  6. Gene regulation transcription: regulated by activators (transcription factors) and repressors (rare in eukaryotes) RNA processing: different exons may be used within one gene, producing different protein products mRNA longevity: mRNA translates as long as it is intact ‘lifespan’ encoded in the 3' UTR sequence AUUUA signals early degradation translation: mRNA may exist without being translated (not well understood)

  7. Mutation potential phenotypic effects of mutation: morphological trait – change in color, size nutritional or biochemical variation – loss of ability to synthesize a protein - synthesis of different versions of a protein change in behavior – e.g., fruitflies -lose ability to recognize mate gender changes in gene regulation - gene turned off, or on lethality – loss of essential function

  8. Mutation Spontaneous mutations – errors in translation, ~ every 106 bases repaired during translation by DNA polymerase ‘checking’ Induced mutations – due to mutagens

  9. Point mutations • Single base substitutions • transitions - purine to purine, or pyrimidine to pyrimidine • transversions - purine with a pyrimidine or vice versa.

  10. Point mutations • Single base substitutions • transitions - purine to purine, or pyrimidine to pyrimidine • transversions - purine with a pyrimidine or vice versa. • The fat cat ate the hot dog. • The fat car ate the hot dog. • The fat cat ate the hot hog. small change in meaning, still readable no change (synonymous or silent mutations) single amino acid change (missense mutation)

  11. Point mutations • frameshift mutations • insertions • deletions

  12. Point mutations • frameshift mutations • insertions • deletions • The fat cat ate the hot dog. • The fma tca tat eth eho tdo g. • Thf atc ata tet heh otd og • includes change in stop codon: • The fat cat ate the hot dog how why fry hot cat the… profound change

  13. Mutation changes in larger segments of genome - tandem duplications addition of duplicate CAG sequences results in Huntington’s chorea - ploidy, aneuploidy

  14. ploidy = number of chromosome sets in cell haploid – 1 (gametes) diploid− 2 (most cells) triploid – 3 (sterile) tetraploid – 4 ....etc. Xenopus tropicalis 2N = 20 diploid Xenopus laevis 2N = 36 tetraploid Xenopus muelleri 2N = 72 octaploid Xenopus ruwensoriensis 2N = 108 dodecaploid

  15. ploidy = number of chromosome sets in cell haploid – 1 (gametes) diploid− 2 (most cells) triploid – 3 (sterile) tetraploid – 4 ....etc. plants tend to have more ploidy levels – can overcome sterility with vegetative reproduction higher ploidy -> larger cells, more ‘product’ - yeast - wheats autopolyploidy vs. allopolyploidy

  16. euploidy = correct number of chromosome sets in cell polyploidy aneuploidy = incomplete set of chromosomes usually due to non-disjunction during meiosis Down’s syndrome (trisomy 21) Patau’s syndrome (trisomy 13) Turner’s syndrome (monosomy of X chromosome) Klinefelter syndrome (trisomy of sex chromosomes, XXY)

  17. euploidy = correct number of chromosome sets in cell polyploidy aneuploidy = incomplete set of chromosomes usually due to non-disjunction during meiosis Down’s syndrome (trisomy 21) Patau’s syndrome (trisomy 13) Turner’s syndrome (monosomy of X chromosome) Klinefelter syndrome (trisomy of sex chromosomes, XXY) which is likely to have more severe effects, monosomy or trisomy?

  18. Inversions – part of chromosome is flipped by 180

  19. Translocations – non-homologous chromosomes exchange material (not always symmetrically)

  20. euploidy = correct number of chromosome sets in cell polyploidy aneuploidy = incomplete set of chromosomes usually due to non-disjunction during meiosis Down’s syndrome (trisomy 21) Patau’s syndrome (trisomy 13) Turner’s syndrome (monosomy of X chromosome) Klinefelter syndrome (trisomy of sex chromosomes, XXY) loss/variation/rearrangement of portions of chromosome Cri-du-chat syndrome (loss of part of arm of chromosome 5)

  21. Mutation Somatic cell mutations – affect only individual Gametic (germline) cell mutations – heritable (e.g., cancer is largely unimportant evolutionarily)

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