Bacterial Chromosome: DNA Structure, Replication, and Segregation Lecture 1 PDF

The Bacterial Chromosome: DNA Structure, Replication, and Segregation LECTURE 1: MICROBIAL GENOME Generalization in Prokaryotes ORGANIZATION  Genomes have a larger number of genes...

The Bacterial Chromosome: DNA Structure, Replication, and Segregation LECTURE 1: MICROBIAL GENOME Generalization in Prokaryotes ORGANIZATION  Genomes have a larger number of genes and are also more complex, I.e., the number of genes reflects the lifestyle. Prokaryotic  Smaller bacteria are specialists, such as obligate parasites and endosybionts, and  Do not have structures surrounded by larger bacteria are generalists, and may membranes even have a certain degree of development,  Few internal structures such as sporulation in bacillus.  One-celled organisms such as Bacteria, Cyanobacteria etc. Genome size and Eukaryotes Genetics vs Genomics  Defined as the C-value or amount of DNA What is genome? per haploid genome, such as the chich GEnomics and DNA sequencing: exists in the nucleus of a spermatozoon. sewuencing reveals not only genes but also how  Called C, for constant or characteristic, to organism functions and its evolutionary history indicate the fact that size is practically constant within a species. mtDNA  Typically circular and double-stranded  Contains genes essential for oxidative Comparison of Genome size in Eukaryotes and phosphorylation and protein synthesis Prokaryotes  Generally has fewer 37 genes in humans  Primarily involved in energy production  Eukaryotes have larger genomes than through oxidative phosphorylation. prokaryotes, except for some endosymbiont or parasitic green algae, which jave very cpDNA small genomes.  Typically exixts in multiple copies per cell  The smallest eukaryotic genome ever  Contains genes involved in photosynthesis sequenced is that of ‘Guillardia theta’, a  Primarily involved in photosynthesis, symbiont red algae, of only 0.55 Mb. converting light energy into chemical  There is a wide range of sizes, much energy greater than that of prokaryotes, more than  Has more genes 80,000-fold larger, from organisms such as yeast (1.2 Mb) to the amoeba (686,000 Mb). Remember!  Both mtDNA and cpDNA are considereed to be the result of ancient symbiotic Is there a relationship between genome size and relationship also known as endosymbiotic complexity of the eukaryotic organism? theory. Why? Because..  Both have double membranes  Large variation in genome sizes between  Both organelles contain their own circular eukaryotic species does not seem to have a DNA relationship with either the complexity of the organism or the number of genes they contain. Genome size and Prokaryotes  Compared with humans, fish, amphibians or plants, have much larger genomes  In prokaryotes (Archaea and Bacteria): linear relationship between genome size and the number of genes. How do you explain the mismatch between the  In what examples do you expect to find the C-values and the presumed amount of genetic smallest genome size? information contained within the genomes of  obligate endosymbiotic eukaryotes? bacteria, symbionts, and  The C-value paradox refers to the parasites perplexing observation that the amount of DNA in a haploid genome (C-value) does The Bacterial Chromosome: DNA Structure, Replication, and Segregation not correlate with the perceived complexity  Symbionts - mutuallybeneficial of an organism. This means that some relationship between a fungus simple organisms, like certain single-celled and another organism protists, can have much larger genomes  Parasites - feeding on living than complex organisms like humans tissue of a host. Parasites that cause disease are called pathogens. Is it possible to produce a minimal genome? HYPHAE  Minimal gene concept  Tubular Design Build Test  Reductive evolution  Hard wall of chitin (same material in Arthropod exokeletons)  Cross walls may form compartments  Multinucleate  Grow at tips FUNGAL SPORES < FUNGAL GENETICS >  Spores - asexual (product of mitosis ) or sexual (product of meiosis) in origin.  Purpose of Spores Characteristics of Fungi  Allow the fungus to move to new food source.  Body form  Resistant stage - allows fungus to  Unicellular survuve periods of adversity.  Filamentous  Means of introducing new genetic  Mycelium combinantions into a population.  Selerotium - hardened mass of mycellium that generally serve as an overwintering stage. Hyphal Growth from Spores  Multicellular, such as mycelial cords, rhizomorphs, and fruit bodies (mushrooms)  Mycelia have a huge surface area.  Trivia: One giant individual of Armillaria ostoyae in Oregon is 3.4 miles in diameter and covers 2,200 acres of forest; at least 2,400 years old, and weighs hundreds of tons  Ten cubic cetimeters of rich organic soil fungal hyphae with a surface area of over 300cm2. Generalized life cycle of fungi  Heterotrophic - “other feeder”  Saprophytes or saphrobes - feed on dead tissues or organic waste(decomposers) The Bacterial Chromosome: DNA Structure, Replication, and Segregation Ascomycota - ‘sac fungi’  Completely sequenced  Few introns - little need for cDNA  Sexual Reproduction - asci (sing = ascus)  Transformable - can put DNA into cells;  Asexual Reprod. - common alter copy number can also take out genes.  Cup fungi, morels. Truffles  Good model System - many genes are  IMportant plant parasites & saprobes conserved between yeast and humans  Yeast- Saccharomyces  Decomposers, pathogens, and found in Yest life cycle most lichens  Haploid Phase Basidiomycota - ‘ club fungi’  Diploid Phase  Sexual Reproduction (Meiosis)  Sexual repro- basidia  Quiescence (Resting) Phase  Asexual reprod - not so common  Long lived dikaryotic mycelia  Rusts & smuts - plant parasites  Mushrooms, polypores, puffballs, boletes, Genetic linkage refers to the tendency of bird’s nest fungi. certain genes to be inherited together because  Enzymes decompose wood, leaves, and they are physically close to each other on the other organic materials same chromosome.  Decomposers, pathogens, and some form mycorrhizal associations with plants. A genetic map, also known as a linkage map, provides a visual representation of the relative Yeasts positions of genetic markers (such as specific genes or variants) along a chromosome.  Single celled fungi  Adapted to liquids Limitations of two point crosses  Plant saps  Water films  Difficult to determine gene order if two  Moist animal tissues genes sre close together  Actual distances between genes do not always add up Yeast as Model Organism  Pairwise crosses are time and labor consuming  The S. cerevisiae yeast has one of the smallest genomes of eukaryotes, being What leads to a recombination frequency of unicellular. 50%?  S.cerevisiae is viable with numerous  A recombination frequency of 50% markers and available in large quantities typically indicates that the two genes are making it cheap to study. located on different chromosomes.  Unicellular, rapid to grow, easily cultured. During meiosis, crossing over between homologous chromosomes can lead to recombination, resulting in the exchange Advantage as an Experimental System of genetic material between the chromosomes. When the genes are  Cheap Media - LB, can grown on plates located on different chromosomes, they or in liquid assort independently, leading to a  Fast developmental time - yeast- 90 min, recombination frequency of 50%, E.coli- 20 min, humans - 20yrs indicating that they are not linked genes.  Well developed genetics - haploid/diploid states; Recombination Linked Genes(