OBQ flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Central Dogma

The flow of genetic information from DNA to RNA (transcription) to protein (translation). DNA replicates itself. RNA is a messenger; proteins are the functional products.

Na+/K+ ATPase

An active transport pump in the plasma membrane that uses ATP to move three sodium ions out and two potassium ions in, maintaining electrochemical gradients.

Michaelis-Menten equation

v = Vmax[S]/(Km + [S]). Km is the substrate concentration at half-maximal velocity; Vmax is the maximum rate when all enzyme is saturated.

Apoptosis

Programmed cell death involving caspase cascades. Intrinsic pathway is mitochondrial (cytochrome c, caspase-9); extrinsic pathway uses death receptors (caspase-8). Both activate caspase-3.

Hardy-Weinberg equilibrium

Allele and genotype frequencies remain constant in an idealized population with no mutation, migration, selection, drift, or nonrandom mating. p² + 2pq + q² = 1.

Recombination frequency

The percentage of offspring showing recombination between two loci. One percent recombination equals one centimorgan (cM). Values below 50% suggest genetic linkage.

X-linked recessive inheritance

Trait caused by a recessive allele on the X chromosome. Affects mostly males; no male-to-male transmission; carrier females may show mild symptoms due to X-inactivation.

Frameshift mutation

An insertion or deletion of nucleotides not a multiple of three, shifting the reading frame and usually producing a truncated, nonfunctional protein.

Glycolysis net yield

Per glucose: 2 pyruvate, 2 NADH, 2 ATP, and 2 H2O produced in the cytosol. Key regulated enzyme is phosphofructokinase-1, inhibited by ATP and citrate.

Oxidative phosphorylation

Electron transport chain pumps protons to create a gradient; ATP synthase uses the proton-motive force to make ATP. Yields about 2.5 ATP per NADH and 1.5 per FADH2.

Competitive inhibition

An inhibitor binds the enzyme active site, competing with substrate. Apparent Km increases; Vmax remains unchanged because high substrate can outcompete the inhibitor.

Henderson-Hasselbalch equation

pH = pKa + log([A-]/[HA]). Describes buffer behavior; a buffer is most effective within about one pH unit of its pKa.

Countercurrent exchange

Blood flows opposite to water across fish gills, maintaining a concentration gradient along the entire exchange surface and maximizing oxygen extraction.

Xylem and phloem

Xylem transports water and minerals upward via transpiration pull and cohesion-tension. Phloem transports sugars from source to sink by pressure flow.

Action potential

A rapid electrical signal in neurons: depolarization from Na+ influx, repolarization from K+ efflux, and refractory periods. Requires reaching threshold (about -55 mV).

Innate vs adaptive immunity

Innate immunity is fast, nonspecific (barriers, phagocytes, inflammation). Adaptive immunity is slower, specific (B cells/antibodies, T cells) and creates immunological memory.

Logistic population growth

dN/dt = rN(1 - N/K), where r is intrinsic growth rate and K is carrying capacity. Growth slows as N approaches K and stabilizes.

Keystone species

A species whose impact on community structure is disproportionately large relative to its abundance. Removal causes major changes in ecosystem composition.

Allopatric speciation

Speciation following geographic isolation of populations. Genetic divergence accumulates via mutation, drift, and selection until reproductive isolation evolves.

Genetic drift

Random changes in allele frequencies due to sampling error, strongest in small populations. Can cause loss of variation and fixation of alleles independent of selection.

Standard error of mean

SE = s/√n, where s is sample standard deviation and n is sample size. It estimates variability of the sample mean and decreases as n increases.

Type I and Type II errors

Type I error is rejecting a true null hypothesis (false positive, probability α). Type II error is failing to reject a false null (false negative, probability β); power = 1 - β.

Chi-square test

Tests whether observed categorical frequencies differ from expected. χ² = Σ[(O - E)²/E]; degrees of freedom = (rows - 1)(columns - 1) for independence.

Correlation coefficient r

Measures strength and direction of linear association between two variables, ranging from -1 to +1. r² is the proportion of variance explained; correlation does not prove causation.

Beer-Lambert law

Absorbance A = εcl, where ε is molar absorptivity, c is concentration, and l is path length. Absorbance is proportional to concentration at a given wavelength.

SDS-PAGE

Protein electrophoresis using sodium dodecyl sulfate to denature and impart negative charge. Proteins separate primarily by molecular mass through a polyacrylamide gel.

Negative and positive controls

A negative control lacks the treatment and establishes baseline. A positive control uses a known effective treatment to verify the assay works. Both validate results.

qPCR Ct value

Cycle threshold: the PCR cycle at which fluorescence exceeds background. Lower Ct indicates more initial template; Ct is inversely related to starting copy number.

Size-exclusion chromatography

Separates molecules by size using porous beads. Large molecules cannot enter pores and elute first; small molecules enter pores and elute later.

Fluorescence microscopy

Uses fluorophores excited at one wavelength and detected at a longer emission wavelength. Filters isolate signals; confocal microscopy improves optical sectioning and reduces out-of-focus light.

Testcross

Crossing an individual of unknown genotype with a homozygous recessive individual. Offspring phenotypes reveal whether the unknown parent was homozygous or heterozygous.

Epistasis

Interaction between genes where one gene masks or modifies the phenotype of another, producing modified Mendelian ratios such as 9:3:4 or 12:3:1.