Fundamental Genetic Organization

Question 1

Chromosomal Genome 101 Basics

Answer 1

• all genomes made of DNA (exception: some viruses)
• genome size: 10^4 (small virus)–> 10^12 bp (amoeba)
• Bacteria: simple OR complex

Question 2

Chromosomal Genome 1-Size/Structure

Answer 2

• large (megabases-avg 4000 genes)
• dbl stranded DNA
• tightly packed structure (nucleoid-NOT surrounded by membrane)
• typically haploid (or singular), circular (LARGE-5million bases), or linear

Question 3

Chromosomal Genome 2-Clinical Relevance

Answer 3

• can code for certain AB resistance and virulence factors

- usually within pathogenicity islands

Question 4

Chromosomal Genome 3-Bounds and Folds

Answer 4

• bound by polyamines and specialized DNA-binding proteins=pack TIGHTLY
• each fold is attached to some central structure and INDEPENDENTLY supercoiled

Question 5

Chromosomal Genome 4-Traditional View

Answer 5

• LIES/SIMPLE BITCH:loosely organized tangled know of DNA (vs highly ordered typical euk chromosome)
• REALITY: with NEW and different nucleiod liberation techniques–>very similar to euk chromosome

Question 6

Chromosomal Genome 5-Stress Induced Structure

Answer 6

a. tightly packed (transcriptionally INACTIVE)

b. coral reef–>supercoiled loop

Question 7

Chromosomal Genome 5-Fundamental Structure

Answer 7

a. 300 nm loop
b. 80 nm fiber
c. 40 nm fiber (transcriptionally INACTIVE)
+histone-like proteins
d. DNA

Question 8

Plasmid (Episomal) Genome 1-Structure/Function

Answer 8

• autonomous, self-replicating, extrachromosomal, supercoiled, dbl-stranded DNA
• TEND TO BE small (kilobases)
• usually circular, but can be linear
• found in most G+/- bacteria
• single cell can have more than one plasmid

Question 9

Plasmid (Episomal) Genome 2-Clinical Relevance

Answer 9

-genes for AB resistance (R plasmids*)
-proteins that confer AB resistance (erythromycin or penicillin)
-genes for virulence factors (pili or toxins)
EASILY TRANSFERRED FROM HOST TO HOST

Question 10

Plasmid (Episomal) Genome 3-Conjugative (Conjugal) Plasmids

Answer 10

• including F and R plasmids
• autonomous transfer themselves hosthost WITHIN or BETWEEN species/generaaa
• clinical relevance: major cause of spread of multiple AB resistances

Question 11

Plasmid (Episomal) Genome 4-NON-conjugated Plasmids

Answer 11

• cannot transfer themselves BUT can be transferred by a conjugative plasmid.
• generally used for genetic engineering because they cannot transfer themselves

Question 12

Plasmid (Episomal) Genome Basics 101

Answer 12

Episome=DNA molecule that replicates independently of chromosomal DNA

Question 13

Bacterial Virus Genome (Bacteriophage, Phage) 1-Structure/Function

Answer 13

• RNA or DNA
• single OR double stranded
• linear OR circular
• size range: 3-300 THOUSAND bases (aka 3-300 KILO bases)

Question 14

Bacterial Virus Genome (Bacteriophage, Phage) 2-Clinical Relevance

Answer 14

Phage genomes can carry genes that encode virulence factors (Diptheria beta toxin or *Cholera toxin)

Question 15

Bacterial Virus Genome (Bacteriophage, Phage) 3-Lifestyle A

Answer 15

• Lytic (productive) Infection
• after infection viral genome replicates and causes the host cell to lyse
• lysage permits progeny viruses to release into the environment

Question 16

Bacterial Virus Genome (Bacteriophage, Phage) 4-Lifestyle B

Answer 16

• Lysogenic (latent or temperate) infection
• lysogenic phage genome=PROPHAGE
• after infection virus DOES NOT replicate because: all the genes necessary for lytic infection become turned off (REPRESSED)=prophage becomes LATENT
• prophages can either:
  a. circularize and remain autonomous like plasmids
  b. integrate into and become part of the host chromosome