Quiz 2 Flashcards
What is the central dogma?
flow of genetic information from DNA to RNA, to protein
What did Fredrick Griffin do to show DNA is the genetic material?
Discovered “transforming factor”; Studied smooth and rough strain in mice cells and found that some factor in S cell (that kills) transformed living R cells into S cells
How did Avery, MacLead, and McCarthy show that DNA is a hereditary material
Took s cells, spun them in centrifuges, heat killed them; took out constituents through filtrate and extracted it to that of a complex mixture; treated with individual enzymes but when done failed to recover just R cells; so degraded complex mixture till only DNA was left and found that it destroyed the transforming principle
People worried if contents in DNA were pure
How did Alfred Hershey and Martha Chase contribute to the finding of DNA as a use of genetic material
infected T2 bacteriophage into E. coli growing in the presence of either 35S to label the protein or in the presence of 32P to label the DNA.
incubated the labelled phage with the E. coli for 20 minutes to allow the genetic material to enter the E. coli.
blended to cell/phage mixture at high speed to knock the phage ghosts off the E. coli.
purified the phage ghosts and the E. coli cells and showed that when the protein was labelled with S35 the label remained outside the E. coli but when the DNA was labelled with P32 the label entered the bacterial cells
labelled DNA but not labelled protein could be recovered in the progeny phage showing DNA and not protein entered the cells
What are the steps for bacteria cell to infect DNA
- Phage attaches to bacterial cell
- Phage injects DNA
- Phage DNA directs host cell to make more phage DNA and protein parts so new phages can form
- Cell lyses and releases new phages (whole process takes a good 20 min)
What do nucleotides contain
Nitrogenous base, 5 carbon sugar, phosphate group
What are purines
Adenine and Guanine
What are Pyrimidine
Cytosine, Uracil, Thymine
What was Chargaff’s Rule
Nitrogenous bases occur in definite ratios; a+g = c+t
Complement base form hydrogen bonds; AT = double bond; GC = triple bond
Who deduced the secondary structure of DNA and how
James Watson and Francis Creek; used Wilkins and Franklins x-ray diffraction (beam directed at molecule in form of solid; positions of atoms are deduced from diffraction patterns produced by film)… but it. was rlly Franklin that determined that the DNA was a helix shape
What is the process of DNA replication
process of two strands unwinding, separating, then acting as a template for new strand to be made through synthesis
What is DNA transcription
- Creates an RNA copy of one strand of DNA
- RNA made in 5’ to 3’ direction using 3’ to 5’ as a template
- Results in RNA that will translated into a protein
Carried out by RNA polymerase; There are specific nucleotide sequences that hint when to start and stop; only introns (protein coding genes for mRNA are translated) exons are removed through splicing
Why are nucleic acids are synthesized 5’ to 3’
This is because the energy to catalyze to formation of the new phosphodiester bond is provided by the hydrolysis of the phosphodiester bonds in ATP, GTP, CTP, and TTP. If we are adding on the nucleotide phosphate, we must be adding that 5’phosphate to the 3’hydroxyl of the chain we are elongating. We synthesize 5’ to 3’, always elongating at the 3’ hydroxyl.
What is DNA translation
Polypeptide synthesis with the use of a ribosome in order to assemble amino acids
What are the characteristics of genetic code
Codon is three nucleotides
AUG - start
UAA, UAG, UGA, - stop
Amino Acids
Linked by polypeptide bond
Structure: amino group, carbon, carboxyl group, hydrogen, R
What are the different mutations
Frame shift: the deletion or insertion of a nucleotide
Missense: wrong protein
Nonsense: premature stop
Silent: change in amino but same protein
What is PCR and how can it be used
PCR - Polymerase chain reaction; amplifies DNA template to mane many DNA copies
- Use RNA genome as template to make a complementary DNA using reverse transcriptase
- enzyme will degrade RNA and make primer
The test uses two sets of primers to amplify two different regions of the viral Nucleocapsid gene.
The test uses one additional set of primers to amplify a region of the human RNAse P gene. If you really had put the swab up your nose you would have collected some nasal epithelial cells containing this gene.
Where do epidemiologist get info from
Public health records, CDC & WHO, US census and bureau
How did Google influence the trajectory of the flu
Google tracked the flow of the flu through ppl searching for flu-like symptoms; was accurate for a while but then ppl started over searching and skewed the data
SIR Model
N = S+I+R
S: # of susceptible ppl
I: # of ppl infected
R: # of ppl recovered/immune
Predictive Epidemic
Model shows equilibrium and predict fraction of individuals infected at anyone time
Cons: enhancements requires more compartments in order to consider more factors
Beta: transmission per encounter
Y: loss rate of immunity
b: death rate
alpha: disease induced mortality
a: per capita birth rate
Basic Reproductive R0
R0 - measure of potential for infectious disease to spread in a pop or its transmission potential
R<1 :disease disappears
R=1 :disease endemics
R>1 :disease epidemic
R0 Dependecy = BKD
Beta= risk of transmission per contact
K= Avg # of contacts per unit
D= duration of infection (1/v)
What is herd immunity threshold
Min proportion of pop that needs to be immunized in order to obtain herd immunity
What are the 5 links of the infectious diseases
- characteristics of infectious organism
- source & or reservoir of the infectious organism
- mode of transmission
- Susceptibility of host
- exit mechanism
What is the difference between a prokaryote, eukaryote, and archea
Prokaryotes: lacking a nucleus and mitochondria; no membrane bound organelles; lack a nucleus, mitochondria, spliceosomal introns and spliceosomes; Possess transcriptionally-coupled translation
Eukaryotes: has membrane bound nucleus
Rna Splicing
Exons retained in finished mRNA while introns are removed
What are the functions of the cytoplasmic membrane
Membrane contains oxidative enzymes that function in cell wall synthesis; Ability to pump nutrients through selective transport and integral membrane protein; secrete toxins & certain enzymes into non extracellular medium
Fatty acid tail (hydrophobic) and phospholipid head (hydrophilic)
What are functions of a cell wall
gives shape and rigidity to cell; prevents lysis; Composed of peptiglycogen polymer > repeating NAM and NAG w/ glycosidic linkage
What is the difference between Gram pos and neg cell walls
Gram Pos: no phospholipid outer membrane; very thick cell wall; teichocic acids polymers and peptidoglycan make up wall
Gram Neg: peptidoglycan layer is thinner; walls contained lipoproteins which attach to the outer membrane; between inner & outer membrane is the perisplasmic space that degrades enzymes that can’t be transported; Outer membrane blocks transport of larger molecules;
What is importance of Gram stain
Way to differentiate type of cell wall; mechanism based on permeability difference caused by thickness;
Steps:
1. flood heatfixed smear w/ crystal violet for 1min - all cell purple
2. add iodine solution for 1 min - all cells remain purple
3. Decolorise w/ alc - gram pos are purple ; gram neg are colorless
4. Counterstain - gram neg are redish; gram pos are still purple
How were viruses described filterable agent
Ivanowski passed tobacco leaf extract through filters that caused tobacco mosaic viruses
What are some of the structural components of viruses
Nucleic acid genomes that can either be DNA or RNA that are single stranded or double stranded)
Caspids made of repeating structural protein that surround genome
Virus Replication Cycle
Attachment: virus -specific protein on virion to receptor on host cell
Penetration: vision or nucleic acid enters cell
Synthesis : virus specific proteins made, viral nucleic acid replicated, more viral protein made
Assembly: Structural units from coat w/ viral nucleic acid & any viral proteins inside
Release: Viral progeny exit cell via lysis or budding
Plaque forming unit
single virus particle infects cell; replicates, destroys, hits neighboring cells; hole/plaque develops overtime; # of hole is plaque forming unit
