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BIO 111 > Chapter 18 > Flashcards

Chapter 18 Flashcards

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Biology 101 flashcards
1
Q

what is a virus?

A
  • non-living
  • requires assistance of living cells for reproduction
  • first discovered- TMV
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2
Q

Viruses

A
  • a small infectious particle
  • nucleic acid enclosed in a protein coat
  • small; 50 million virus particles could fit in one of our cells
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3
Q

host range (differences among viruses)

A

number of species and cell types that can be infected

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4
Q

structural (differences among viruses)

A
  • all have a capsid (protein coat)- varies in shape and complexity
  • some have viral envelope- from host cell plasma membrane
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5
Q

genome can be… (differences among viruses)

A
  • DNA vs. RNA
  • single stranded vs. double stranded
  • linear vs. circular
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6
Q

viral reproductive cycle- basic steps

A
  • attachement
  • entry
  • integration (depends on virus type)
  • synthesis of viral components
  • viral assembly
  • release
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7
Q

Attachment (viral reproductive cycle)

A
  • usually specific for certain cell type

- binds to membrane protein -> receptor for something else

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8
Q

Entry (viral reproductive cycle)

A
  • bacteriophages (or phage) injects nucleotides into bacteria
  • may also inject proteins to copy or integrate genes
  • some viral genes expressed immediately
  • virus may proceed to synthesis of viral components OR integrate into host chromosome
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9
Q

Integration (viral reproductive cycle)

A
  • viral gene codes for integrase- cuts host DNA, inserts viral genome
  • phage in bacterial DNA called prophage
  • may excise later and proceed to synthesis
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10
Q

Synthesis (viral reproductive cycle)

A

-host cell enzymes make many copies of the phage DNA and transcribe the genes within these copies into mRNA

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11
Q

Assembly (viral reproductive cycle)

A
  • some self-assemble- TMV

- other are too complicated to self-assemble, require help from proteins

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12
Q

release (viral reproductive cycle)

A

-phages must lyse hose cell to escape

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13
Q

latency

A
  • some viruses integrate their genomes into a host chromosome
  • every time this cell divides, each daughter cell is carrying the integrated viral genome..
  • prophage or provirus remains inactive or latent
  • HIV and some herpes viruses can remain silent for years
  • most viral genes silenced
  • known as lysogenic cycle
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14
Q

Lysogenic cycle

A
  1. phage injects its DNA into cytoplasm
  2. phage DNA integrates into host chromosome
  3. prophage DNA is copied when cell divides
  4. on rare occasions, a prophage may be excised from host chromosome
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15
Q

lytic cycle

A
  1. phage injects its DNA into cytoplasm
  2. phage DNA directs the synthesis of many new phages
  3. cell lyses and releases the new phages
  4. new phages can bind to bacterial cells
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16
Q

HIV

A
  • 2 copies of single stranded RNA and two molecules of reverse transcriptase
  • packaged into a capsid
  • surrounded by a viral envelope
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17
Q

the case of HIV

A
  • entry: HIV fuses with host cell membrane
  • it binds to receptors on T-cells
  • integration: HIV is an RNA virus, i.e. a retrovirus
  • uses viral reverse transcriptase to make complementary DNA strand that will be template for double stranded viral DNA
  • synthesis: HIV DNA is not excised from host chromosome, but it transcribed in the nucleus to produce many copies of viral RNA
  • translated to make viral proteins and RNA for new viral particles
18
Q

retrovirus

A
  • use reverse transcription
  • reveres transcriptase lacks a proofreading function
  • makes more errors and tends to create mutant strains of HIV
  • constant production of new viral proteins which our immune system has difficulty keeping up with
19
Q

controlling HIV

A
  • because HIV mutates so frequently
  • vaccines hard to develop
  • “cocktail” of drugs
  • hard for immune system to recognize/ combat
20
Q

genetics of Bacteria

A
  • circular chromosome
  • 1 origin of replication
  • sometimes > 1 copy
  • 1-4 identical chromosomes
  • # depends on bacterial species and growth conditions
21
Q

bacterial chromosomes

A

-may contain repetitive sequences interspersed throughout

22
Q

nucleoid ( genetics of bacteria)

A
  • where DNA hangs out

- not membrane bound

23
Q

bacterial chromosomes (genetics of bacteria)

A
  • small
  • few thousand genes
  • mostly structural genes
24
Q

bacteria can also have plasmids

A
  • small, circular pieces of DNA, NOT part of bacterial
  • what sort of advantages do plasmids provide?
  • occur natural in many strains of bacteria
  • also found in a few eukaryotes, such as yeast
  • replication independently of bacterial chromosome
  • not usually necessary for survival but can provide growth advantages
  • episome- plasmid that can integrate into bacterial chromosome
25
Q

resistance plasmids

A

(R factors

-genes that confer resistance against antibiotics/ toxins

26
Q

degradative plasmids

A

-genes that enable bacteria to digest and use unusual substances

27
Q

col-plasmids

A

-genes that encode colicines; proteins that kill other bacteria

28
Q

virulence plasmids

A

-genes that turn a bacterium into a pathogenic strain

29
Q

fertility plasmids (F factors)

A

allow bacteria to mate with each other

30
Q

reproduction in bacteria

A
  • very fast
  • E.coli can divide every 20 min
  • single cell-> bacterial colony in < 1 dat
  • reproduce by binary fission
  • no sexual reproduction -> no meiosis
  • plasmids replicate independently of chromosome
31
Q

binary fission

A
  • chromosome replicates
  • cell beigns to divide with one chromosome at each end
  • cell wall forms between the two new cells
  • gives rise to two daughter cells -> genetically identical
32
Q

genetic diversity

A
  • different types of the same bacterial species = strains
  • genetic diversity caused by 1. spontaneous mutations
  • alters bacterial genome and affects traits of bacterial cells
  • one E. coli strain may be resistant to pencillin, another may be sensitive
  • genetic diversity caused by 2. genetic transfer
  • from one bacterial cell to another
  • ex: plasmid conferring antibiotic resistance transferred from a resistant cell to a senseitive cell
33
Q

conjugation (genetic transfer)

A

-direct transfer of DNA from donor to recipient cell

34
Q

transformation (genetic transfer)

A

DNA from the environment is taken up by another bacteria

35
Q

transduction (genetic transfer)

A

a virus transfers genetic information from one bacterium to another

36
Q

conjugation: a bit more than kissing

A
  • 5% of E.coli strains found in nature can act as donor strains
  • donor strains contain a fertility factor (F factor) that can be transferred to recipients
37
Q

F factors

A
  • several genes required for conjugation
  • found on a plasmid
  • may also confer a growth advantage
  • 2 types of cells
  • F+ cells have an F factor
  • F- cells do not
  • sex pili made by F+ cells that bind specifically to F- cells
  • sex pili shorten, brining cells close and they conjugate
  • F strand in F+ cell replicates and is transferred to recipient cell
38
Q

transformation

A

-no contact between cells
-bacteria pick up DNA from environment
-from dead bacteria
-cells need competence factors (genes) that facilitate
-binding of DNA fragments to the bacterial cell surface
0uptake of DNA
-incorporation of foreign DNA into the bacterial chromosome

39
Q

transformation; competence factors

A
  • proteins coded for by a set of genes
  • a DNA receptor gene
  • DNA cutting enzymes
  • DNA channel/ uptake proteins
  • enzymes to integrate the new DNA into the bacterial chromosome
40
Q

transduction

A
  • viruses that infect bacteria transfer bacterial genes from one bacterium to another
  • occurs when virus gets stuffed with the wrong DNA and then tries to infect another cell

BIO 111 (17 decks)

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