Microbial Physiology and Genetics (Ch. 7)

What is an episome?

A plasmid that can stay in the cytoplasm or integrate itself into the chromosome

When is bacterial DNA replicated and why?

Before binary fission so that daughter cells are identical to parent

What causes Diphtheria? How is the toxin acquired? Some other examples of bacteria this can happen to...

By a toxin made by Gram- positive Corynebacterium diphtheriae C. diphtheriae + corynebacteriophage (tox gene) = toxigenit strain *lysogeny* Strep. pyogenes, C. botulinum, and V. cholerae

What's a silent/neutral mutation?

Causes no change to cell/enzymatic function

What occurs in transformation? What did Oswald Avery study in regards to this? Is it common in nature? What's special about transformation?

Competent cells take in "naked DNA" fragments Live uncapsulated took up dead capsulated and made it alive (pneumoniae) NO May occur between different species

When do spontaneous mutations occur? What is the rate expressed as? What's the average rate of mutation?

Constantly throughout bacterial genome frequency of mutation 1 per every 10^6 DNA reps

How does conjugation happen?

Donor F+ attached sex (F) pilus to recipient F- Relaxase: enzyme that nicks F plasmid and guides DNA

What is transduction and how does it occur? What are the types if transduction?

Moving genetic info from one bacteria to another via a bacteriophage: Temperate bacteriophage inserts itself into the bacterial chromosome - making a prophage which activates and assembles the virus - viral DNA and bacterial DNA are then moved to other bacteria via bacteriophage 1. Generalized Transduction 2. Specialized Transduction

What increases mutation rate? Some examples of them.

Mutagen: UV light & radioactive substances

What is a beneficial mutation and one example

One that helps an organism survive its environment; antibiotic resistance *without change it would die*

What is a mutant?

Organisms with the mutation

What is the basic process of genetic engineering? What can we use genetically engineered bacteria for?

Transfers eukaryotic genes into easy to culture cells through plasmid and make gene products *like insulin* Help clean enviro, better food, and antibiotics

How does the Ames test work/what does it test for? What does it mean if a back mutation occurs?

Uses a mutant strain of Salmonella to test if chemicals or food additives are a mutagen. That chemical is a mutagen. Could be carcinogenic. *back mutation = positive reading for Ames test*

Genotype/genome

complete collection of genes

Genes that are: always expressed expressed when needed

constitutive genes inducible genes

How many chromosomes do bacteria have and what do they look like? What are to characteristics about them?

one, it's circular and continuous. It's dsDNA and lack protiens

What specifies a mutation?

If a gene alteration is passed to a daughter cell

What is gene therapy? Most common method for gene insertion?

Inserting normal genes into cells to correct genetic disorders Viral insertion; bacteria and synthetic vectors being tested

Two categories of lysogenic conversion

1. Virulent/lytic: always leads to lytic cycle - death 2. Temperate/lysogenic: DNA from phage is inserted into chromosome but no lytic cycle occurs, gives cell new phenotype *forms lysogenic cell *

What is a plasmid and what can it do to the cell?

Extrachromosomal DNA that stays in the cytoplasm; can change the cell by gaining genes

How are bacterial genes made?

Gene - mRNA - gene product; through transcription and translation

What kind of bacteria use conjugation? What gene is often spread through conjugation/ what can it create?

Gram-negative bacilli R-factors *antibiotic resistant* making superbugs

What's the difference between harmful and lethal mutations?

Harmful: produces nonfunctional enzymes Lethal: when those nonfunctional enzymes were necessary for life - the cell dies *can be both or just harmful*

What type of mutation are most mutations?

Silent/neutral

Genetics:

Study of heredity

What's a bacteriophage? What's a lysogenic cell? What is lysogeny? What's a prophage?

virus that infects bacteria bacterial cell + phage DNA = lysogenic cell phage's DNA mixed into chromosome and multiplying Phage after DNA integrates and is passed to daughter cells