Ch08a lect microbial genetics
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Transcript of Ch08a lect microbial genetics
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