Microbiology Exam 4 Part 3

Bacterial Genetics

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