The nucleoid
Location of associated proteins and chromosome
Shape of the nucleoid
Irregularly shaped region, usually not membrane bound
The nucleoid contains usually...
One circular, double-stranded DNA molecule
Plasmids
Extra-chromosomal DNA
Plasmids contain...
Usually closed circular, small DNA molecules and few genes (non-essential)
Plasmids exist and replicate ___ of chromosome
Independently
DNA composed of...
4 bases or nucleotides
In DNA, adenine goes with...
Thymine
In DNA, cytosine goes with...
Guanine
Bond between adenine and thymine
Double hydrogen bond
Bond between cytosine and guanine
Triple hydrogen bond
Discovered DNA structure
Watson and Crick (1953)
Discovered DNA as the genetic material
Griffith (1928), Avery, Macleod, and McCarthy (1944), and Hershey and Chase (1952)
Gene
DNA segment that codes for a polypeptide, rRNA, or tRNA
Notation for gene
First three letters lower case and italicized, and last letter upper case and italicized
Notation for gene protein
First and fourth letters upper case followed by the word protein
Genotype
Specific set of genes an organism possess (the nucleotide sequence)
Phenotype
Set of observable characteristics
Example of gene
hisC
Example of gene protein
HisC protein
Examples of phenotype
His+ or His-
Wild-type strain
Strain inoculated from nature
Mutation
Heritable, stable change in nucleotide sequence
Wild-type strain is designated as ___ form
Non-mutant
With mutation, genotype is...
Altered
Mutation ___ have an effect on the phenotype of an organism
May or may not
Examples of mutation
hisC1, hisC2, etc.
Most prevalent form of a gene
Wild-type
Forward mutations
Wild-type _ mutant form
Example of forward mutations
Prototroph _ auxotroph
Prototroph _ autotroph is a ___ mutation
Nutritional
Reverse mutations
Mutant phenotype _ wild-type phenotype
Example of reverse mutations
Auxotroph _ prototroph
Revertants
Same-site and second-site
Suppressor mutations (revertants?)
Second-site revertants
Detection and isolation of mutants
Screen, selectable mutations, and selection
Screening
Detecting mutants via observation
Selectable mutations
Confer some type of advantage to the organisms that possess them (e.g., drug resistance)
Selectrion
Placing organisms under conditions where the growth of those with a particular genotype will be favored
Negative selection
Mutants cannot grow