Chapter 4.3 Genetic Elements: Chromosomes and Plasmids

Question 1

The entire compliment of genes in a cell or virus is called what?

Answer 1

Genome

Question 2

What is the main genetic element in prokaryotes?

Answer 2

Chromosomes

• Other genetic elements include virus genomes,
plasmids, organellar genomes, and transposable
elements

Question 3

Viruses contain either RNA or DNA genomes, what shape and stranding can they contain?

Answer 3

Linear or circular

Single or double stranded

Question 4

What replicate separately from chromosome?

Answer 4

Plasmids

• Great majority are double-stranded
• Most are circular
• Generally beneficial for the cell (e.g., antibiotic
resistance)
• NOT extracellular, unlike viruses

Question 5

___________ is a genetic element with “housekeeping” genes

Answer 5

Chromosomes

• Presence of essential genes is necessary for a genetic
element to be called a chromosome

Question 6

What is a genetic element that is expendable and rarely contains genes for growth under all conditions?

Answer 6

Plasmids

Question 7

Bunch of nonsense information about E. Coli that you may need

Answer 7

• The Escherichia coli chromosome
• Escherichia coli is a useful model organism for the
study of biochemistry, genetics, and bacterial
physiology
• The E. coli chromosome from strain MG1655 has
been mapped using conjugation, transduction,
molecular cloning, and sequencing
• Some features of the E. coli chromosome
• Many genes encoding enzymes of a single biochemical
pathway are clustered into operons
• Operons are equally distributed on both strands
• ~5 Mbp in size
• ~40% of predicted proteins are of unknown function
• Average protein contains ~300 amino acids
• Insertion sequences (IS elements)

Question 8

Genetic elements that replicate independently of host chromosomes.

Give characteristics of them

Answer 8

Plasmids

• Small circular or linear DNA molecules
• Range in size from 1 kbp to >1 Mbp; typically less than
5% of the size of the chromosome
• Carry a variety of nonessential, but often very helpful,
genes
• Abundance (copy number) is variable
• A cell can contain more than one plasmid
• Genetic information encoded on plasmids is not
essential for cell function under all conditions BUT
may confer a selective growth advantage under
certain conditions

Question 9

What are characteristics of R plasmids?

Answer 9

• Resistance plasmids; confer resistance to antibiotics
and other growth inhibitors
• Widespread and well-studied group of plasmids
• Many are conjugative

Question 10

What are proteins that are produced by bacteria that inhibit or kill closely related species?

Answer 10

Bacteriocins