Chapter 17: The Simpler Genetic Systems of Viruses, Bacteria, and Archaea Flashcards
Why are viruses considered nonliving?
17.1
- not composed of cells
- do not use energy or carry out metabolism
- do not maintain homeostasis
- do not reproduce
What is the protein coat found in all viruses known as?
17.1
capsid; which encloses a genome consisting of one or more molecules of nucleic acid
What does the viral envelope consist of?
17.1
a lipid bilayer that is derived from a cellular membrane of the host cell and is embedded with virally coded spike glycoproteins
Are viral genomes diversive?
17.1
Yes. They may be single or double stranded, circular or linear, and composed of DNA or RNA.
What occurs in Step 1 of the viral reproductive cycle?
17.2
the virus attaches to the surface of a host cell
What occurs in Step 2 of the viral reproductive cycle?
17.2
the viral genome enters the host cell
What occurs in Step 2 of the viral reproductive cycle?
17.2
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
Once integrated, the phage DNA is a bacterium is called a what?
17.2
prophage
What are the functions of the enzyme integrase?
17.2
- insert the viral genome into the chromosome
- cut the host’s chromosomal DNA
What occurs in Step 4 of the viral reproductive cycle?
17.2
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
What occurs in Step 5 and 6 of the viral reproductive cycle?
17.2
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
The coronavirus that causes COVID-19 is a ____ virus with a ____ genome.
17.2
enveloped; RNA
Try to draw out the viral reproductive cycle. Look up images to see if you’re correct. :)
17.2
There are two cycles that bacteriphages may follow. What are they?
17.2
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
How do emerging viruses arise?
17.2
they typically arise via mutations in pre-existing viruses (ex: COVID, influenza, zika, HIV)
The genome of a typical bacterium consists of a ____ chromosome that carries a few ____ genes.
17.3
circular; thousand
The region of a bacterial cell where the chromosome is tightly packed is know as the?
17.3
nucleoid region
What processes lead to bacterial chromosome compaction?
17.3
supercoiling and chromosome loops
How can you describe the archaeal chromosome structure in regards to bacterial and eukaryotic chromosomes?
17.3
Some archael chromosomes share structural features with bacterial chromosomes while others are similar to eukaryotic chromosomes.
Many bacterial cells have DNA-containing ____ that are separate from the bacterial chromosome.
17.3
plasmids
What are the 5 categories of plasmids?
17.3
- resistance plasmids
- degradative plasmids
- col-plasmids
- virulence plasmids
- fertility plasmids
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
bacterial colony
Are plasmids needed for survival?
17.3
No, but they can provide growth advantages
Know the functions of each category of plasmids.
17.3
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
