Lecture 45: Introduction to Prokaryotic Genetics Flashcards
Why do we study bacterial genetics?
Understanding basics of molecular biology
and genomics
Understanding bacterial ecology
Application in biotechnology
Understanding human health and disease
When did Mendel publish his work on peas?
1866
When did Lamarck state that ‘species are not fixed, they change over time’?
1800
When did Darwin go on his voyage of the beagle?
1831- 1836
When did Darwin publish his ideas of evolution and natural selection in the Origin of Species?
1859
When did Beadle and Tatum come up with ‘one gene, one enzyme’?
1941
Who came up with the ideas of bacterial inheritance?
Luria Delbruck in 1943
When did Hershey and Chase come up with the idea that DNA is functional?
In 1953
When were new recombinant DNA technologies discovered?
In the 1970s
Who discovered the features of the genetic code and when?
Nirenberg in 1961
When was recombinant human insulin approved for use on diabetics?
In 1982
When was the Human Genome sequenced?
In 2003
When was the first genome of a free living organism (Heamophilus influenzae) sequenced?
In 1995
What is bacterial genetics?
the study of the mechanisms of heritable information in bacteria, their chromosomes, plasmids, transposons
What techniques have enabled the study of bacterial genetics?
culture in defined media, replica plating, mutagenesis, transformation, conjugation and transduction.
How much of the DNA on earth is Bacteria DNA estimated to make up?
Bacteria DNA estimate to make up 30% of DNA on earth
Is it true that the human body contains approximately as many bacterial cells as eukaryotic cells?
Yes
Our focus will be on bacteria as model organisms underpinning our understanding of genetics, molecular biology and biochemistry and biotechnology
Importance in health and disease and ecology covered in other modules
Why are bacteria good model organisms?
- They’re haploid, so they carry only one copy of the chromosome.
- They undergo asexual reproduction, so there’s no issue of recombination between generations.
- They have a short generation time
- They grow on plates and liquid culture with defined media.
- It’s easy to store stocks of bacteria
- It’s easy to manipulate bacteria genetically
Describe the bacterial genome
A single circular, double stranded DNA chromosome
Does the genome size of bacteria vary between different bacterial species?
Yes
Which bacteria doesn’t have a single circular, double stranded DNA chromosome?
Borrelia burgdorfei (which causes Lyme disease). Instead, it has a linear, single chromosome
Are introns common in bacteria?
No, they’re extremely rare
Do bacteria have much inter-gene space?
No. In comparison, eukaryotes have a lot more inter-gene space.
Where are functionally related genes grouped?
In operons
Do bacteria often carry plasmids?
Yes
Describe plasmids
They’re circular, extra-chromosomal, and they replicate DNA independently
How big is the E.coli genome?
4.6 Mbp (encoding 4277 genes)
What is binary fission?
- Asexual reproduction
- Cell elongates and all content increased
- DNA replicated and segregated
- 2 identical daughter cells arise
What is the generation time of E.coli under optimal conditions?
Approximately 20 minutes
What is the generation time of Clostridium perfringens ?
app 10 min (one of the fastest known)
What does Clostridium perfringens cause?
food poisoning and several severe conditions such as gas gangrene
Is it true that some extremely slow growing bacteria may only divide once in 1000s of years?
Yes
Is it true that E.coli is capable of synthesising all cellular components from simple inorganic nutrients and a carbon/energy source (minimal media)?
Yes
What is the typical minimal media composition of E.coli?
- K2HPO4 and KH2PO4 phosphate for pH control
- (NH4)2SO4 for Nitrogen
- MgSO4, Binds to nucleotides, nucleic acids and needed in proteins
- CaCl2, Probable roles in sensing and membrane transport
- Trace metals, Often important in protein function
- Glucose, as a source of carbon and energy
