Housekeeping

1
Housekeeping

• Updated syllabus on web
• Download a new syllabus
• Exam week from Friday (4/11)
• Review session? Wednesday at 6 pm

2
Updated syllabus
Week
Readings
Topic
3/31-4/4
pp..462-470, pp.390-406
Genomes
4/7-4/11
Genomes and Exam
pp.470-477, 481-483, Parts of Ch12
4/14-4/18
DNA Technology
Worksheet will explain
DNA Technology
4/21-4/25
Worksheet will explain
Gene Regulation
Ch 15 and Ch 16
4/28-5/2
3
What is a polycistronic message? What is a
polyribosome?
4
How does gene expression differ in eukaryotes
and prokaryotes?
5
The key differences
Prokaryotes
Eukaryotes

• No nucleus (transcription and translation
  coupled)
• No introns
• Promoter
• RNA polymerase (one type) sigma factor
• Terminates transcription at the terminator signal
• Dont modify mRNA
• Different sized ribosomes
• mRNA can carry multiple genes (multiple ribosome
  start sites)

• Nucleus (transcription and translation are not
  coupled)
• Exons and introns
• Promoter
• RNA polymerase (several types) transcription
  factors
• Terminates transcription after the terminator
  signal
• Modify their mRNA
• Different sized ribosomes
• mRNA carries one gene (one ribosome start site)

6
How do mutations affect gene expression?
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Mutations in the coding sequence
Fig. 7.21a
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Mutations outside the coding region
Fig. 7.21b
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Mutations in gene expression machinery

• Polymerases, tRNAs, rRNAs, sigma factors,
  transcription factors, regulatory factors
• Can affect the expression of many different
  genes!!

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Gene expression
Fig. 7.2
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How does DNA carry genetic information?
How does DNA replicate to pass on to offspring?
How does the DNA change to allow for so much
diversity?
How does DNA encode for a phenotype?
12
Understanding the Genome
13
Organisms composed of cells
Maintenance
Function
Reproduction
Replace dead cells
Make proteins
Make gametes
Express genes
Meiosis
Mitosis
Regulate gene expression
DNA Replication
DNA Replication
14
What we know about DNA? DNA IS OUR HEREDITARY
INFORMATION

• Inherit traits
• Traits determined by genes
• Genes located on chromosomes
• Chromosomes made of DNA

15
How are chromosomes organized?
How does chromosome organization affect cell
function?
What happens when chromosome organization
changes?
16
Chromosome organization and function
Prokaryotes
Eukaryotes
Changes in the chromosome!
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Why do we care about prokaryotes?
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Fig. 13.1
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Why prokaryotes?

• Disease
• Maintain environment
• We cant survive without them!
• Evolution (VERY DIVERSE)
• over 10,000 species
• Industry (Metabolic diversity)
• Easy to study
• Grow quickly
• Grow in large s
• Grow on agar/broth (easy environments)
• Simple organism (get a genetic foundation)

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OVER 100 prokaryotic genomes completed/underway!
E. coli best understood bacterium Sequence
published in 1997
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What did they find in E. coli??

• Identified 4000 ORFs
• Identified intergenic regions (tRNAs, rRNAs,
  noncoding sequence)
• Identified chromosome arrangement

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What did they find in E. coli??
40 ORFs (4000 total) no known function!!
ORF unique to E. coli (not been studied yet)
ORF present in other bacteria (not been studied
yet)
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Whats my point??
LOTS TO LEARN!!!!
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In general, what is a bacterial chromosome
composed of?

• HAPLOID
• CIRCULAR CHROMOSOME
• 1 Mbps -6 Mbps
• DENSE!

25
Genes on both DNA strands (mRNA sequence)
tRNA
rRNA (3 types)
90 encodes for genes
Genes back to back
NO INTRONS
Not a lot of intergenic regions
Not many repeat sequences
26
Genes on both DNA strands (mRNA sequence)
rRNA (3 types)
Leftover 10?
rRNAs
tRNAs
Regulatory sequence
Noncoding sequence-no function known
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What are plasmids?
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The plasmid
Fig. 13.8

• Circular piece of DNA
• 1000 bp to 3 Mbps
• Encodes genes
• NOT ESSENTIAL FOR BACTERIAL SURVIVAL!
• Expand capabilities of bacteria

29
If we better understand genetics of prokaryotes,
then we better understand

• Disease
• Maintain environment
• We cant survive without them!
• Evolution (VERY DIVERSE)
• over 10,000 species
• Industry (Metabolic diversity)