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UW-Madison BIOLOGY 151 - Regulating gene expression in Eukaryotes

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BIO 151 1st Edition Lecture 22 Outline of Last Lecture - From genotype to phenotype- Point mutation- Insertion or deletion mutations- Controlling gene expression- Gene expression in bacteriao Repressible operono Inducible operonOutline of Current Lecture - Regulating gene expression in Eukaryoteso Chromatin modification- Controlling gene expressiono Distal control elementso mRNA degrading/translationo Mutations- Cell cycle and mitosiso Chromosomeso Ploidy Current Lecture- Regulating gene expression in eukaryoteso Nucleus DNA packing/unpacking Transcription initiation RNA processing- Capping, tailing, splicing (alt. splicing can create many domains of geneo Cytoplasm mRNA stability Translation Protein stability Protein targeting These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- These are ways cells control gene expression- Controlling gene expressiono Chromatid Modification Histone proteins pack DNA in chromatid Chemical modification, like acetylation, loosens the packaging and exposes DNA for transcriptiono Transcription factors: bind promoter and proximal control elements; can activate or inhibit transcription (chunks of DNAtranscription factors  can inhibit) Flaking elements: proximal control elements Types of transcription factors- Stimulate transcription: bind enhancer element- Repress transcription: bind silencer element Distal control elements: enhancer and silencer elements can be thousands of bases from promoter- Upstream- Downstream- In introns- Still affect RNA polymer because of two groups (DNA binding proteins and mediator proteins  determines whether DNA synthesis happenso mRNA degrading/translation mircroRNA’s (miRNA): ~22 bases long- type of non-coding RNA- binds mRNA if at least 7-8 bases complement- stops translationo translation blocked ribosome can’t read double stranded DNA and complex falls apart- Mutations and gene expressiono Exon mutation Silent Missense Nonsenseo Regulatory region mutation in Eukaryotic cells mutation happens everywhereo Change recognition sites for transcription factor binding Mutate enhancer=less/no gene expressed Mutate repressor = gene turned on which shouldn’t be turned on  Gain binding site for a different transcription factor; improper control of gene expression- Genes: short segments within long DNA molecules that are packaged into chromosomeso Chromosomes: shuttle for genes; shuttle genetic info to offspringo Genes passed from parent to offspring because chromosomes are passed from parent to offspringo DNA replication produces 2 sister chromatids Sister chromatids: identical strings of DNA joined at centromere; considered one chromosome- Cell cycle and mitosis: “duplicate and divide”o S phase: chromosome duplication, each chromosome now consists of 2 sister chromatidso G1, G2: cell growso Mitosis: divide chromosomes in nucleuso Cytokinesis: cytoplasm division- Chromosomes and ploidyo Humans: 23 of chromosomes Most cells have 2 chromosomes of each type (diploid number of chromosomes of each type) Ploidy: number of chromosomes of each type Each chromosome in a pair is called a homolog; not identical copies- Each homolog has same genes, but different primary sequence (diff amino acids)o Ploidy must remain constant Animals must keep ploidy constant Haploid or tetraploid embryos don’t survive (not the case in plants, just humans) Exception: 1 extra chromosome: Trisomy 21= down syndrome- Collective name for extra health conditions person has to live witho How is ploidy kept constant? Reproduction- Fertilization: gametes fuse- M gamete + F gamete= zygoteo 2n+2n=4n WRONG!!!- Gametes are haploid (n)= each has 23 chromosomes o N(23) + n(23) =2n (46)- Haploid (n)- Diploid (2n)- Diploid zygote (2n=46)  mitosis  multicellular diploid adults (2n =46) To make gametes, ploidy is reduced  MEIOSIS: cuts gametes in half- Meiosis: reduces ploidy in half, fertilization doubles ploidy- Mitosis vs. Meisoso Mitosis: DNA replicates (I)…1 cell division (PMAT) One 2n cell two 2n cells Conservation division ploidy conservedo Meiosis: back to back mitosis, but no interphase (no DNA replication) before second division 1-PMAT-PMAT 2nd division reduces ploidy two 2n cells  four 1n


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UW-Madison BIOLOGY 151 - Regulating gene expression in Eukaryotes

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