Biology 151 1st Edition Lecture 24 Outline of Last Lecture 1. Complications with Mendelian inheritance2. Recombination3. What if a gene is on a sex chromosome (sex-linked)?4. X-linked diseases in humans5. Side issue: What do you do with 2 X chromosomes?6. Random X Chromosome inactivation blocks transcription, creates genetic "mosaic"7. What if inheritance is non-Mendelian?8. Nondisjunction and gene "dosage" problemsOutline of Current Lecture 1. Polyploidy 2. Imprinting3. Genes in semi-autonomous organelles - mitochondria, chlorplasts4. Non-DNA information?5. Semi-autonomous organelles6. Respiration7. What's all this about electrons?8. GlycylosisCurrent Lecture- nondisjunction - errors in chromosome separation ("disjunction") during meiosisPolyploidy:- 3n, 4n, etc. - too many of all chromosomes- can result from -- failure in meiosis- polyspermy (too many sperm at once)- mitosis without cytokinesis- not as rare as you might think during plant and animal evolution - zebrafish have 2X genes of some other fish- polyploids somatic cells sometimes produced by mitosisImprinting:- reversible, sex-specific change in gene expression (transcription) passed on to offspring- addition of methyl groups to nucleotides silences transcription- local state of DNA methylation can be passed on during mitosis: old methylated strand acts as a signal to methylate the newly synthesized strand- specific genes methylated, silenced in sperm or egg, but not both (depends on the gene)- offspring always inherit one silenced allele of that gene from one parental sex- methylation removed during offspring's meiosis, but then...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.- the gene is methylated, silenced in sperm or eggs, but not both- ex. lgf2 gene silenced by methylation in haploid egg, but not in sperm- methylation maintained in fetus of either sex after fertilization, so like inheriting non-functional gene - methylation imposed on both alleles when making egg, removed from both alleles when making spermGenes in semi-autonomous organelles - mitochondria, chloroplasts:- sperm do not (or rarely) donate organelles during fertilization, so organelle genes are inherited maternally- single egg can have different organelles with different mutations- mitochondrial ancestry, "Eve" = 200,000 years agoSemi-autonomous organelles:- where most of the ATP comes from in eukaryotic cells- the energy to make ATP comes from catabolic reactions that are exergonic- ATP hydrolysis provides the energy for cellular processes that are endergonic- mitochondria - produce chemical energy from sugars, other compounds- chloroplasts - in plants and some protists (single-celled eukaryotes)- sites of production of energy = photosynthesis- respiration of the monosaccharide glucose via a series of enzyme-catalyzed reactions- respiration is a spontaneous reaction, but you'd have to wait a long timeRespiration:- glycolysis - in cytoplasm, not mitochondria- 6 carbon glucose "lysed" into 2 3-carbon pyruvates, get ATPs and high energy electrons- pyruvate enters Krebs (Citric Acid) Cycle- in mitochondrial matrix- broken into CO2s, get ATPs and high energy electrons- oxidative phosphorylation: in mitochondrial membrane, high energy electrons and O2 -> ATP- lots of steps, each catalyzed by a separate protein enzyme- glycolysis and Krebs Cycle make ATP by making phosphate from high energy "substrate" (reactant) molecule, binding to ATP- substrate-level phosphorylationWhat's all this about electrons?:- Redox reaction - atom that gains electrons is reduced, atom that loses electrons is oxidized- electron carriers reduced by high energy electrons- need a "pool" of ADP and Pi to get ATP (usually from using ATP in energy-requiring reaction)- need a "pool" of NAD+ to get NADH (usually from oxidation of NADH in mitochondrion)Glycolysis:- have glucose, want to make pyruvates- glucose makes 2 pyruvates- 1) initial steps require phosphates from 2 ATPs (energy investment phase)- later steps in glycolysis produce -- 2) 4 ATPs- 3) electrons captured in NADH- 4) 2 3-carbon pyruvates- Know this...- 1) initial steps require phosphates from 2 ATPs- later steps produce...- 2) 4 ATPs- 3) electrons captured in 2 NADHs- one 6-carbon glucose produces 2 3-carbon pyruvates (glyco-lysis = sugar splitting- Yields: 2 ATP and 2
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