MicrobiologyB.E Pruitt & Jane J. Stein

AN INTRODUCTIONEIGHTH EDITION

TORTORA • FUNKE • CASE

Chapter 8, part A

Microbial Genetics

Terminology• Genetics Study of what genes are, how they

carry information, how information is

expressed, and how genes arereplicated

• Gene Segment of DNA that encodes a functional product, usually a protein

Terminology• Genome All of the genetic material in

a cell• Genomics Molecular study of

genomes• Genotype Genes of an organism• Phenotype Expression of the

genes

E. coli

Figure 8.1a

Flow of Genetic Information

Figure 8.2

• Polymer of nucleotides: adenine, thymine, cytosine, guanine

• Double helix associated with proteins

• "Backbone" is deoxyribose-phosphate

• Strands held together by hydrogen bonds between AT and CG

• Strands are antiparallel

DNA

Figure 8.4

DNA

Figure 8.3

DNA

Figure 8.5

• DNA is copied by DNA polymerase– In the 5 3 direction– Initiated by an RNA primer– Leading strand synthesized continuously– Lagging strand synthesized discontinuously – Okazaki fragments – RNA primers are removed and Okazaki

fragments joined by a DNA polymerase and DNA ligase

– See web sites• http://bioteach.ubc.ca/TeachingResources/MolecularBiology/DNAReplication.swf • http://www.ncc.gmu.edu/dna/repanim.htm • http://www.mun.ca/biology/scarr/3250_DNA_replication_&_transcription.htm

• http://www.nobel.se/medicine/educational/dna/a/replication/replication_ani.html • http://www.nobel.se/medicine/educational/dna/a/replication/lagging_ani.html

DNA

DNA

Figure 8.6

• DNA replication is semiconservative

DNA

Figure 8.7

• DNA is transcribed to make RNA (mRNA, tRNA, and rRNA)

• Transcription begins when RNA polymerase binds to the promotor sequence

• Transcription proceeds in the 5 3 direction

• Transcription stops when it reaches theterminator sequence

• Web sites:– http://www.nobel.se/medicine/educational/dna/b/transcription/

Transcription

Figure 8.8

RNA processing in Eukaryotes

Figure 8.12

• mRNA is translated in codons (3 nucleotides)

• Translation of mRNA begins at the start codon: AUG

• Translation ends at a STOP codon: UAA, UAG, UGA

Translation

Figure 8.2

Translation

Figure 8.9