Micro 106 Exam 3

What is a mutation

Change in base sequences of DNA and RNA

what are the causes of mutations

chemical and physical

* simple error
* chemical → carcinogens
* radiation

Differences and similarities between prokaryotic and eukaryotic transcription / translation

* Start codon in both AUG (but eukaryote use different for of methionine)
* Each eukaryote mRNA codes for just one protein (introns / exons)
* Prokaryote mRNA often have several genes in series
* Nucleus and mRNA

what is generation time

time it takes for population to double

What are the types of mutatoins?

* point
* missense
* frameshift
* base analog
* silent

what is a silent mutation

what is a point mutation?

* single base substitution
* changing one base
* no loss or gain of bases
* one codon may change

what is a missense mutation

affects proteins

* single base sub alters genetic code
* produces an amino acid different from the usual amino acid at that position

what is a frameshift mutation

more serious

* loss of 1 nucleotide would affect downstream reading
* many causes, such as UV

what is a base analog mutation

* chem that resembles nucleotide
* inserts into DNA in replication
* “confuses” DNA polymerase and makes determining appropriate base difficult

what is a nonsense mutation

protein letter changed to stop codon

what is one way to test for mutations?

Ames test

what is the Ames test?

* test for mutagenic properties of a chemical
* look for change in organism’s phenotype
* looks for organism to produce something it wouldn’t unless DNA mutated
* determines if more testing is worth it

what does the Ames Test use to test for mutations?

strain of salmonella that cannot produce histidine

do mutagens = carcinogens?

no but 90% correlation

what is the repair mechanism of cells?

* cells have enzymes that find and repair mutations
* thymine dimer formation with UV light exposure
* 2 enzyme complex

what do the 2 enzymes do in the repair mechanisms of cells?

1st: removes dimer

2nd: inserts correct bases

what is a mutation caused by a virus called?

microorganisms

why are mutations important: HPV

vaccine given to children to protect against mutations when older due to papillomavirus exposure

what is HPV?

* one of most common sexually transmitted infections in US
* estimated to affect \~80 million people
* vaccine only preventative

what are the three mutations possible

1. faulty, non-functional proteins
2. change in protein function
3. non significant change in protein/function

what are the three forms of horizontal gene transfer?

1. conjunction
2. transformation
3. transduction

what is conjunction?

* transfer of plasmid or other genetic material by direct connection
* G- and G+ can conjugate
* significant biomedically
* antibiotic/drug resistance transfer

what is an F+ cell

cell that grows the pilus

what happens in G- cells?

* Fertility (f factor): plasmid from donor that direct pilus formation
* recipient cell has site for pilus
* pilus contracts and pulls cell together

what happens in G+ cells?

* opening created between 2 cells
* replicated DNA passed from one to other

what is an F- cell?

cell that lacks the pilus

what is transformation?

* bacteria acquire new ability from mutations
* acquire gene from somewhere else → competent

what does recombinant mean?

2 portions of DNA combined to form something new

what happens when a chromosome is released from lysed cell?

breaks into fragments that can be absorbed by other cells

what is a competent cell?

cells capable of accepting genetic material

what is some useful recombinant DNA technology

* cells don’t have to come in contact
* no special appendages required

what is transduction?

* allows gene transfer from 1 bacterial cell to another
* Virus accidently transfers genes

what is a bacteriophage?

virus that specifically attacks bacteria

can virus replicate alone?

no, need host

what is generalized transduction?

* DNA transferred from one bacterium to another
* can result in new gene(s)
* random DNA fragments can enter phage

what are the types of transduction

specialized or general

what is specialized transduction?

* viral genes incorporate into host chromosome
* virus can take bit of bacterial DNA with it after lytic cells
* transfer of viral genes and bacterial genes to new cell
* initially transfers bacterial genes from one cell to another

where is transduction commone?

virulent and temperate phages

* lytic or lysogenic cycle

what is generalized transduction simply?

phage can carry any part of DNA

what is specialized transduction?

phage carries only specific parts of DNA

what are transposons?

* transposable elements
* shift from one part of genome to other
* can replicate prior to jumping
* scramble genetic code

describe “jumping genes”

jump from…

* one part of genome to other
* chromosome to plasmid
* plasmid to chromosome

are viruses cellular?

no, obligate intracellular parasites

* non living, cannot replicate transcribe or translate DNA

what are characteristics of viruses? (4)

* can seize control of healthy cell
* can interfere with genes
* large diverse population
* highly specific

what estimated % of our genome is viral?

10%

what is a prion?

potion of a protein that can infect cells

how are viruses easiest to see?

special staining and EM

how do viruses and bacteria compare size wise?

viruses are 10-1000x smaller

what is the structure of a virus?

nucleic acid surrounded by capsid

do all viruses have a capsid?

yes!

what is a capsid?

* made of capsomeres
* distinct shape when assembled
* helical or icosahedral

what is a nucleocapsid?

capsid + nucleic acid it surrounds?

what is an envelope

capsid covered by lipid membrane

what does a capsid do?

* protects virus
* helps gain entry into cell
* can have protein spikes that aid in attachment

what are outer structures made of and what does that mean for shape?

proteins, definite 3D shape

* easily targeted by immune systems

what does virus genetic info look like?

* can be RNA or DNA
* doesn’t have to be double strand but can be
* don’t need many genes

what is the function of viral genes?

overtaking host and reproduction

what do retroviruses start with?

RNA

what is a helical capsid?

rod-shaped capsomers bound together to form series of hollow discs resembling bracelet

what is a naked helical capsid?

very rigid and tightly wound into cylinder package

what are desirable characteristics of germicides

* solubility in solvent
* broad spectrum
* non corrosive
* rapid action

what is an enveloped helical capsid?

more flexible and tend to be arranged as loose helix within envelope

what is a icosahedral capsid?

3D, 20-sided figure with 12 comers

what are complex capsids?

found in viruses that infect bacteria, may have multiple types of proteins and take shapes that are not symmetrical\`

can complex capsids be enveloped

NEVER

what are the processes of the lytic cycle?

* absorb
* penetration of nucleic acids
* viral replication
* assembly release

what are characteristics of the lytic cycle?

* can be slow release of virus from host cell
* possibly no destruction
* persistent/latent infection

where is the lysogenic cycle?

* can be seen in viruses of all types
* first noticed in bacteriophages

what are processes of the lysogenic cycle?

* absorption
* penetration
* synthesis
* assembly
* release

why do we grow viruses?

* study their structure and function?
* ID specific stains
* prepare vaccines

how are viruses grown?

with a host cell

* plant/animals viruses grown in culture and virus added
* also can grow in eggs

how does the flu spread

in air, very contagious

what does the flue virus look like?

* enveloped virus


* glycoprotein spikes
* helical capsid
* enters host by endocytosis

what does hemagglutinin (HA) do?

RBC clumping

attachment and entry

what do neuraminidase (NA) do?

helps virus release new from host cells

what is antigenic drift?

* minor changes allow virus to evade immune system
* missense mutations causes shape change but not function

what is antigenic shift?

* only in type A strain
* major changes due to rearrangements of RNA segments
* different species

what are characteristics of the flu?

* acute fever causes
* self-limiting
* targets respiratory tract lining
* death due to secondary bacterial infectons

what impacts spread/power of virus

* virulence of strain
* immunity of population

what are the criteria for a pandemic

easily transmissible

* variety not seen in humans before

describe avian flu

* humans can get infected\` by it
* takes longer exposure
* typically cannot jump to humans

what is biotechnology?

* uses technology to alter genes of living organisms

what is biotechnology used?

* make more effective crops easier to grow in certain conditions
* learn about generations of organisms
* produce medically useful drugs from proteins difficult to acquire
* combat disease

who started the idea of gene maniplation?

Gregor Mendel (plants) and Watson & crick (DNA structure)

what has polymerase chain reactios does dor DNA analysis?

made it faster

* allows for studying of small amounts of DNA

what happens have the polymerase chain reaction?

sequencing

* determine base order

what is the human genome project?

* originally could sequence large segments of DNA
* wanted to determine what genes do
* 2003 - generated 92% human genome sequence with gaps
* 2022 first complete human genome

what is the restriction enzyme?

* naturally in bacteria
* used to cut DNA to reuse nucleotides
* specific cutting, looks for sequences

what is the genome similarity of humans and … mice? rice? C elegans?

80%

60%

30%

what is the structure of bacteria?

* circular chromosome
* plasmid

what is recombinant plasmid/vector creation?

* way to deliver gene to target cell
* ideal way to incorporate a gene from an outside source into bacteria

how are recombinant plasmid/vector created ?

1. acquire plasmid
2. cut with restriction enzyme
3. use enzyme to cut DNA and plasmid
4. plasmid possibilities


1. original
2. with target genes
3. with non target genes
5. passing electrical current through cells created homes plasmid passes through
6. growing bacteria to locate colony with target genes

what is human gene therapy?

insertion of genes that correct function of mutated genes

what is sterilization

destruction of all organisms on or in something

* includes all on surface or in a fluid

what is disinfection

reduces pathogen number to harmless levels

* no longer able to cause disease, but dot not sterilize

what is antiseptic

chemical used externally on tissue to destroy/inhibit growth of microorganisms

what is disinfectant

chemical used to clean surfaces

* generally too harsh on tissue, won’t destroy spores

what is sanitation

mechanical process of removing microorganisms, reducing contamination to safe levels

what is least resistant?

enveloped viruses