Usmle 1 Behavioral Science And Biochemistry

Front 1

What study "compares a group of people with disease to a group without disease?"

What measure is reported?

Back 1

case-control study

Odds ratio (OR)

Front 2

What study "compares a group with a given exposure or risk factor to a group without such an exposure or risk factor?"

What measure is reported?

Back 2

cohort study

Risk ratio (RR)

Front 3

What study "collects data from a group of people to assess frequency of disease and related risk factors?"

What measure is reported?

Back 3

cross-sectional study

measures prevalence

Front 4

What study "compares the frequency with which both monozygotic twins or both dizygotic twins develop the same disease?"

What does this measure?

Back 4

twin concordance study

measures heritability

Front 5

What study "compares siblings raised by biological vs. adoptive parents?"

What does this measure? (2)

Back 5

adoption study

measures heritability and influence of environmental factors

Front 6

What describes the following stages of clinical trial?
Phase I
Phase II
Phase III
Phase IV

Back 6

Phase I - small number of healthy volunteers to assess safety, toxicity, pharmacokinetics
Phase II - small number of patients with disease to assess treatment efficacy, optimal dosing, adverse effects
Phase III - large number of patients assigned drug or placebo, comparing new drug to standard treatments
Phase IV - postmarketing surveillance for rare or long-term effects

Front 7

Sensitivity and specificity are fixed properties of a test. However, what 2 measures will vary with the prevalence or pre-test probability?

Back 7

PPV and NPV vary

Front 8

What is "proportion of all people with disease (positive in gold standard) who test positive, or the probability that a test detects disease when it is present?"

What is the formula?

Back 8

sensitivity = TP/(TP +FN)

SNOUT - SeNsitivity rules diseases OUT

Front 9

What is "proportion of all people without disease who test negative, or the probability that a test indicates non-disease when it is absent?"

What is the formula?

Back 9

specificity = TN/(TN + FP)

SPIN - SPecificity rules diseases IN

Front 10

What is "probability that a person with a positive test result actually has the disease, or the proportion of test results that are true positive?"

What is the formula?

How does this relate to prevalence and pre-test probability?

Back 10

PPV = TP/(TP + FP)

PPV varies directly with prevalence and pre-test probability (high prevalence or pre-test probability = high PPV)

Front 11

What is the "probability that a person with a negative test result actually does not have the disease, or the proportion of test results that are true negatives?"

What is the formula?

How does this relate to prevalence and pre-test probability?

Back 11

NPV = TN/(TN + FN)

NPV varies inversely with prevalence and pre-test probability (low prevalence or pre-test probability = low NPV)

Front 12

What is greater for chronic diseases, prevalence or incidence?

Back 12

prevalence > incidence for chronic diseases

Front 13

In standard 2x2 square with diease on top and risk factor on left, what is equation for OR (odds ratio)?

Back 13

OR = (a/c)/(b/d) or ad/bc

Front 14

In standard 2x2 square with diease on top and risk factor on left, what is equation for RR (relative risk)?

Back 14

RR = a/(a+b)/c(c+d)

Front 15

What is formula for number needed to treat?

Back 15

number needed to treat = 1/absolute risk reduction

absolute risk reduction = number of people who get flu without flu shot - number who get flu with flu shot

Front 16

What is the formula for number needed to harm?

Back 16

number needed to harm = 1/attributable risk

attributable risk = risk in exposed group - risk in unexposed group

(if risk of lung cancer in smokers is 21% and risk of lung cancer in non-smokers is 1%, then attributable risk of smoking for lung cancer is 21-1 = 20%)

Front 17

What is "the consistency and reproducability of a test (reliability)?"

What type or error reduces this?

Back 17

precision

random error reduces precision of a test

increased precision = decreased standard deviation

Front 18

What is "trueness of test measurements (validity)?"

What kind of error reduces this?

Back 18

accuracy

systematic error reduces accuracy

Front 19

What is "stating that there is a difference when none actually exists (mistakenly accepting H1, when H0 is real)?"

Back 19

alpha (Type I error)

Front 20

What is "stating there is no difference when one actually exists (mistakenly accepting H0 when H1 is real)?"

Back 20

beta (Type II error)

Front 21

What waveform is associated with the following sleep patterns?

Awake (eyes open)
Awake (eyes closed)
N1 (5%)
N2 (45%)
N3 (25%)
REM (25%)

Back 21

BATS DB (drink blood)

awake eyes open - beta (highest freq, lowest amp)
awake eyes closed - alpha
N1 - theta
N2 - sleep spindles
N3 - delta (lowest frequency, highest amplitude)
REM - beta

Front 22

What is the principal NT for REM sleep?

Back 22

Ach

Front 23

What 2 amino acids are most common in histones?

Back 23

lysine, arginine (they are positively charged, so the negative DNA is attracted to them)

Front 24

What chromatin is highly condensed?

Back 24

HeteroChromatin (HC - highly condensed)

Front 25

What does DNA methylation of cytosine and adenine do?

Back 25

methylating template strand cytosine and adenine allows DNA mismatch repair enzymes to know which strand is parent and daughter

this only occurs in prokaryotes

Front 26

What does histone methylation do?

What does histone acetylation do?

Back 26

histone methylation inactivates transcription of DNA (Methylation makes DNA Mute)

histone acetylation relaxes DNA coiling, allowing transcription (Acetylation makes DNA Active)

Front 27

Higher G-C content of DNA makes for higher melting temperatures. Why?

Back 27

3 hydrogen bonds between C-G takes more energy to separate

Front 28

What 4 anti-neoplastic and antibiotic drugs inhibit purine synthesis?

Back 28

1. 6-MP (blocks de novo purine synthesis)
2. 5-FU (inhibits thymidylate synthase)
3. MTX (inhibits dihydrofolate reductase)
4. Trimethoprim (inhibits bacterial dihydrofolate reductase)

Front 29

What disease "is defective purine salvage due to absence of HGPRT, which results in excess uric acid and de novo purine synthesis, causing retardation, self-mutilation, hyperuricemia, and gout?"

How is it inherited?

Back 29

Lesch-Nyhan syndrome

X-linked recessive

HGPRT (He's Got Purine Recovery Trouble)

Front 30

What type of DNA point mutation causes an early stop codon?

Back 30

non-sense mutation (Stop this nonsense!)

Front 31

How do fluoroquinolones work?

Back 31

inhibit prokaryotic DNA gyrase (DNA topoisomerase)

Front 32

What does DNA Pol III do?

DNA Pol I?

Back 32

DNA Pol III - makes DNA 5' -> 3'

DNA Pol I - degrades RNA primer, replacing it with DNA 5' -> 3'

Front 33

What do TATA and CAAT boxes do?

Back 33

promoters - bind RNA polymerase upstream of gene locus to start transcription

Front 34

What cell cycle stage do p53 and hypophosphorylated Rb inhibit?

Back 34

inhibit G1 -> S

Front 35

What is the site of synthesis of secretory proteins?

Back 35

RER

Front 36

What is the site of steroid synthesis and detoxification of drugs?

Back 36

SER

Front 37

How do griseofulvin, vincristine, vinblastine, paclitaxel, and cohchicine work?

Back 37

inhibit microtubules

Front 38

What syndrome has "mutation of lysosomal trafficking regulator gene, resulting in recurrent pyogenic infections, partial albinism, and peripheral neuropathy?"

Back 38

Chediak-Higashi syndrome

Front 39

What disease is "immotile cilia due to dynein arm defect, resulting in male infertility, decreased female fertility, bronchiectasis, and recurrent sinusitis?"

Back 39

Kartagener's Syndrome (primary ciliary dyskinesia)

associated with situs invertus (congenital defect - major visceral organs are on opposite side of body)

Front 40

What syndrome has "problems with Type IV collagen, so basement membranes in kidney, ears, and eyes are affected, causing nephritis, deafness, and ocular disturbances?"

Back 40

Alport Syndrome

Front 41

What 2 amino acids are common in elastin?

Back 41

proline, glycine

Front 42

How is elastin broken down?

How does alpha-1-antitrypsin deficiency cause disease?

Back 42

elastin is degraded by elastase

elastase is normally inhibited by alpha-1-antitrypsin

alpha-1-antitrypsin deficiency can't inhibit elastase, so elastin is broken down quickly

Front 43

What do Southern, Northern, and Western blots examine?

What about Southwestern blot?

Back 43

SNoW DRoP

Southern - DNA
Northern - RNA (mRNA)
Western - protein


Southwestern - DNA-binding proteins

Front 44

How does indirect ELISA work?

Back 44

sees if antibodies are in the blood

indirect has antigen on the wells, so it tests to see if your antibody will bind them. Then you wash with radiolabled anti-human antibody that will bind to the antibodies bound to the antigen

Front 45

How does direct ELISA work?

Back 45

sees if antigen is in blood.

the well has antibodies on it that bind to antigen in the sample

Front 46

When gene is too small to be seen by karyotype, what test is used?

Back 46

FISH

Front 47

What is rate-determining enzyme in glycolysis?

Back 47

phosphofructokinase-1 (PFK-1)

Front 48

What is rate-determining enzyme in gluconeogenesis?

Back 48

fructose-1,6-bisphosphatase

Front 49

What is rate-determining enzyme in TCA cycle?

Back 49

isocitrate dehydrogenase

Front 50

What is rate-determining enzyme in glycogen synthesis?

Back 50

glycogen synthase

Front 51

What is rate-determining enzyme in glycogenolysis?

Back 51

glycogen phosphorylase

Front 52

What is rate-determining enzyme in HMP shunt (pentose phosphate pathway)?

Back 52

glucose-6-phosphate dehydrogenase (G6PD)

Front 53

What is rate-determining enzyme in de novo pyrimidine synthesis?

Back 53

carbamoyl phosphate synthetase II

Front 54

What is rate-determining enzyme in de novo purine synthesis?

Back 54

glutamine-PRPP amidotransferase

Front 55

What is rate-determining enzyme in urea cycle?

Back 55

carbamoyl phosphate synthetase I

Front 56

What is rate-determining enzyme in fatty acid synthesis?

Back 56

Acetyl-CoA carboxylase (ACC)

Front 57

What is rate-determining enzyme in beta oxidation?

Back 57

carnitine acyltransferase I

Front 58

What is rate-determining enzyme in ketogenesis?

Back 58

HMG-CoA synthase

Front 59

What is rate-determining enzyme in cholesterol synthesis?

Back 59

HMG-CoA reductase

Front 60

What is mnemonic for TCA cycle?

Back 60

"Can I Keep Selling Sex For Money, Officer?"

C - citrate
I - isocitrate
K - a-ketoglutarate
S - succinyl CoA
S - succinate
F - fumarate
M - malate
O - oxaloacetate

also remember succiNATE is LATE (comes after succinyl coA)

Front 61

What is the most common urea cycle disorder?

How is it inherited?

Back 61

ornithine transcarbamoylase deficiency

x-linked recessive (only males express it)

Front 62

What gram positive cocci are catalase +?

Catalase differentiates staph from strep spp.

Back 62

staph are catalase +

Front 63

What gram positive cocci are catalase -?

Catalase differentiates staph from strep spp.

Back 63

strep are catalase -

Front 64

What group of strep has partial hemolysis?

complete?

no hemolysis?

Back 64

alpha - partial (s. pneumoniae, viridans) - form green ring on blood agar

beta - complete (s. pyogenes, s. agalactiae)

gamma - no hemolysis (enterococcus)

Front 65

What is the only catalase and coagulase positive coccus with beta hemolytic properties?

Back 65

staph aureus (forms clear zones on blood agar)