Chapter 17: The Simpler Genetic Systems of Viruses, Bacteria, and Archaea

Question 1

Why are viruses considered nonliving?

17.1

Answer 1

• not composed of cells
• do not use energy or carry out metabolism
• do not maintain homeostasis
• do not reproduce

Question 2

What is the protein coat found in all viruses known as?

17.1

Answer 2

capsid; which encloses a genome consisting of one or more molecules of nucleic acid

Question 3

What does the viral envelope consist of?

17.1

Answer 3

a lipid bilayer that is derived from a cellular membrane of the host cell and is embedded with virally coded spike glycoproteins

Question 4

Are viral genomes diversive?

17.1

Answer 4

Yes. They may be single or double stranded, circular or linear, and composed of DNA or RNA.

Question 5

What occurs in Step 1 of the viral reproductive cycle?

17.2

Answer 5

the virus attaches to the surface of a host cell

Question 6

What occurs in Step 2 of the viral reproductive cycle?

17.2

Answer 6

the viral genome enters the host cell

Question 7

What occurs in Step 2 of the viral reproductive cycle?

17.2

Answer 7

viruses that are capable of integration carry a gene that codes an enzyme called integrase; the gene is expressed after entry and the inegrase cuts the host’s chromosomal DNA and inserts the viral genome into the chromosome

Question 8

Once integrated, the phage DNA is a bacterium is called a what?

17.2

Answer 8

prophage

Question 9

What are the functions of the enzyme integrase?

17.2

Answer 9

• insert the viral genome into the chromosome
• cut the host’s chromosomal DNA

Question 10

What occurs in Step 4 of the viral reproductive cycle?

17.2

Answer 10

the production of new viruses by a host cell involves the synthesis of new copies of the viral genome and the viral proteins that make up the protein coat

Question 11

What occurs in Step 5 and 6 of the viral reproductive cycle?

17.2

Answer 11

after all the necessary components have been synthesized, they are assembled into new viruses

the last step is the release of new viruses from the host cell

Question 12

The coronavirus that causes COVID-19 is a ____ virus with a ____ genome.

17.2

Answer 12

enveloped; RNA

Question 13

Try to draw out the viral reproductive cycle. Look up images to see if you’re correct. :)

17.2

Question 14

There are two cycles that bacteriphages may follow. What are they?

17.2

Answer 14

lytic: new phages are made and the bacterial cell is lysed
lysogenic: the integrated phage of DNA, called prophage is replicated along with the DNA of the host cell

Question 15

How do emerging viruses arise?

17.2

Answer 15

they typically arise via mutations in pre-existing viruses (ex: COVID, influenza, zika, HIV)

Question 16

The genome of a typical bacterium consists of a ____ chromosome that carries a few ____ genes.

17.3

Answer 16

circular; thousand

Question 17

The region of a bacterial cell where the chromosome is tightly packed is know as the?

17.3

Answer 17

nucleoid region

Question 18

What processes lead to bacterial chromosome compaction?

17.3

Answer 18

supercoiling and chromosome loops

Question 19

How can you describe the archaeal chromosome structure in regards to bacterial and eukaryotic chromosomes?

17.3

Answer 19

Some archael chromosomes share structural features with bacterial chromosomes while others are similar to eukaryotic chromosomes.

Question 20

Many bacterial cells have DNA-containing ____ that are separate from the bacterial chromosome.

17.3

Answer 20

plasmids

Question 21

What are the 5 categories of plasmids?

17.3

Answer 21

• resistance plasmids
• degradative plasmids
• col-plasmids
• virulence plasmids
• fertility plasmids

Question 22

When placed on a solid growth medium in a petri dish, an E. coli cell and its daughter cells undergo repeated cellular divisions and form a clone of genetically identical cells called a:

17.3

Answer 22

bacterial colony

Question 23

Are plasmids needed for survival?

17.3

Answer 23

No, but they can provide growth advantages

Question 24

Know the functions of each category of plasmids.

17.3

Answer 24

R factors: contain genes that confer resistance against antibiotics and other toxins
Degradative: enable digestion and utilization of an unusual substance
Col: encode colicins, proteins that kill other bacteria
Virulence: turn a bacterium into a pathogenic strain
Fertility: allow bacteria to transfer genes to each other

Question 25

Through what process do most bacteria and archaea rapidly produce new cells?

17.3

Answer 25

binary fission; asexual reproduction (try to draw it out)

Question 26

In asexual species, genetic diversity arises by what?

17.4

Answer 26

gene transfer and mutation

Question 27

Bacterial cells commonly contain chromosomal DNA and what else?

17.3

Answer 27

plasmids

Question 28

Gene transfer occurs in three different ways. What are they?

17.4

Answer 28

conjugation, transformation and transduction

Question 29

Define conjugation.

17.4

Answer 29

involves direct physical interaction between two prokaryotic cells; one cell acts as a donor and transfers DNA to a recipient cell

Question 30

Define transformation.

17.4

Answer 30

process in which DNA is released into the environment and taken up by another cell

Question 31

Define transduction.

17.4

Answer 31

occurs when a virus infects a prokaryotic cell and then a newly made virus transfers some of that cell’s DNA to another cell

Question 32

Draw out all three processes and be able to lable each step.

17.4

Answer 32

Look up pictures for reference.

Question 33

Conjugation, transformation, and transduction are all examples of?

17.4

Answer 33

horizontal gene transfer