TheMcGraw-HillCompaniesChapter 9MicrobialGeneticsFoundationsinMicrobiologyEIGHTHEDTTIOKathleenParkTalaroBarryChessCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Chapter 9 Microbial Genetics Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Genetics andGenesGenetics - the study of heredityThe science of genetics explores:1. Transmission of biological traits from parent tooffspring2.Expression and variation of those traits3.Structure and function of genetic material4.How this material changes2
2 Genetics and Genes Genetics – the study of heredity The science of genetics explores: 1. Transmission of biological traits from parent to offspring 2. Expression and variation of those traits 3. Structure and function of genetic material 4. How this material changes
Levels ofStructureandFunctionoftheGenomeGenome - sum total of genetic material of a cell(chromosomes + mitochondria/chloroplasts and/or plasmids)- Genome of cells -DNA- Genome of viruses - DNA or RNADNA complexed with protein constitutes the genetic materialas chromosomesCopyright The McGraw-Hil Companies, Inc. Permission required for reproduction or dis playCell levelOrganism levelChromosome levelMolecular levelTAGCCGTATAGCGCCC
3 Levels of Structure and Function of the Genome • Genome – sum total of genetic material of a cell (chromosomes + mitochondria/chloroplasts and/or plasmids) – Genome of cells – DNA – Genome of viruses – DNA or RNA • DNA complexed with protein constitutes the genetic material as chromosomes T T GC A CG TA T CG GC CG T A G C C G C A A A A T C G Organism level Cell level Chromosome level Molecular level Copyright © The McGraw -Hill Companies, Inc. Permission required for reproduction or display. © PhotoLink/Photodisc/Getty Images RF
MicrobialGenomesBacterial chromosomes are a single circular loopEukaryotic chromosomes are multiple and linearCopyright The McGraw-HillCompanies, Inc. Permission required for reproduction or displayCellsProkaryoteEukaryote(composite)-Chromosomes-NucleusNucleolusChromosomePlasmidsMitochondrionPlasmid(insomeVirusesfungi and迷protozoa)ExtrachromosomalDNARNADNAChloroplast4
4 • Bacterial chromosomes are a single circular loop • Eukaryotic chromosomes are multiple and linear Microbial Genomes Chromosomes Nucleus Mitochondrion Nucleolus Extrachromosomal DNA Chloroplast Chromosome Plasmids DNA RNA Plasmid (in some fungi and protozoa) Cells Prokaryote Viruses Eukaryote (composite) Copyright © The McGraw -Hill Companies, Inc. Permission required for reproduction or display
GenesChromosome is subdivided into genes, the fundamental unit ofheredity responsible fora giventraitSite on the chromosome that provides information for acertain cell functionSegment of DNA that contains the necessary code tomake a protein or RNA moleculeThree basic categories of genes:1.Genes that code for proteins - structural genes2.Genes that code for RNA3.Genes that control gene expression - regulatory genes5
5 Chromosome is subdivided into genes, the fundamental unit of heredity responsible for a given trait – Site on the chromosome that provides information for a certain cell function – Segment of DNA that contains the necessary code to make a protein or RNA molecule Three basic categories of genes: 1. Genes that code for proteins – structural genes 2. Genes that code for RNA 3. Genes that control gene expression – regulatory genes Genes
Genotypesand Phenotypes: All types of genes constitute the geneticmakeup - genotypeThe expression of the genotype createsobservable traits - phenotype6
6 • All types of genes constitute the genetic makeup – genotype • The expression of the genotype creates observable traits – phenotype Genotypes and Phenotypes
Genomes Vary in SizeSmallest virus -Copyright The McGraw-Hi Companies, Incquired fiorreproductionofdisolay4-5 genesE.coli-single chromosomecontaining 4,288genes; 1 mm; 1,000xlonger than cellHuman cell -46chromosomescontaining 31,000genes; 6 feet;180,000X longer thancell
7 Genomes Vary in Size • Smallest virus – 4-5 genes • E. coli – single chromosome containing 4,288 genes; 1 mm; 1,000X longer than cell • Human cell – 46 chromosomes containing 31,000 genes; 6 feet; 180,000X longer than cell
DNATwo strands twisted into a double helixBasic unit ofDNA structure is a nucleotideEach nucleotide consists of 3 parts:-A5 carbon sugar-deoxyribose- A phosphate group- A nitrogenous base -adenine, guanine, thymine,cytosineNucleotides covalently bond toforma sugar-phosphatebackbone- Each sugar attaches to two phosphates - 5'carbonand 3'carbon8
8 DNA • Two strands twisted into a double helix • Basic unit of DNA structure is a nucleotide • Each nucleotide consists of 3 parts: – A 5 carbon sugar – deoxyribose – A phosphate group – A nitrogenous base – adenine, guanine, thymine, cytosine • Nucleotides covalently bond to form a sugar-phosphate backbone – Each sugar attaches to two phosphates – 5′ carbon and 3′ carbon
CopyrightTheMcGraw-Hill Companies,inc.PermissionrequiredforreproductionordisplayBackboneDeoxyriboseDNAsugar NbaseHydrogenbondsPhosphateDNADNACondensedmetaphasechromosomedouble helixChemicaltagsattachedtoDNAwrappedaroundhistoneproteinsmayincreasethehistoneswithlinkerDNAexpressionofnearbygenesbetweenthemDNANucleosome-HistoneSupercoiledcondensedchromatinCondensednucleosomesLooselycondensedUncondensedchromosomechromatinfiberChromatin9
9 Hydrogen bonds Backbone DNA Phosphate N base Deoxyribose sugar P P P P P P A T C G G C D D D D D D D Copyright © The McGraw -Hill Companies, Inc. Permission required for reproduction or display. Condensed metaphase chromosome Supercoiled condensed chromatin Loosely condensed chromosome Uncondensed chromatin fiber DNA double helix Chromatin Condensed nucleosomes DNA Chemical tags attached to histoneproteins may increase the expression of nearby genes. Histone Nucleosome DNA wrapped around histones with linker DNA between them DNA
FEXDNACooviohtoThecfionordsnlamssionfeauiredNitrogenous basescovalently bond to the 1'carbon of each sugar andspan the center of theSugalNitrogerphosphathnsnhatemolecule to pair with anappropriatecomplementaryPhosphatebaseontheotherstrandaoxvnboseithcarbonnumbeCytosine- Adenine binds to thymineGuaninwith 2hydrogen bondsThymireidenir-Guanine binds to cytosineHy drogenbondwith 3 hydrogen bondsCovalentbondAntiparallel strands 3'to 5and 5' to 3'10(a)
10 DNA • Nitrogenous bases covalently bond to the 1′ carbon of each sugar and span the center of the molecule to pair with an appropriate complementary base on the other strand – Adenine binds to thymine with 2 hydrogen bonds – Guanine binds to cytosine with 3 hydrogen bonds • Antiparallel strands 3′to 5′ and 5′ to 3′ 3′ P 5′ Phosphate Deoxy ribose with carbon number Cy tosine Guanine Thy mine Adenine Hy drogen bond Cov alent bond A T G C P 5′ 4′ 1′ 2′ 3′ D 3′ D P 5′ OH Sugar phosphate Nitrogen base pair Sugar phosphate P N G N-H N H-N Sugar NH H N A H-N N H H Sugar N-H CH3 T H C (a) N N O O H H H H H N N O O 3′ P 5′ 3′ D OH 5′ 4′ 2′ 1′ Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. N C G C C