OBQ key terms

The flow of genetic information from DNA to RNA to protein. DNA is replicated, transcribed into messenger RNA, and translated by ribosomes into a chain of amino acids that folds into a functional protein.

The enzyme-driven synthesis of an RNA molecule using a DNA strand as a template. RNA polymerase reads the template and builds a complementary RNA copy that can be processed and used by the cell.

The ribosome-catalyzed process in which messenger RNA codons are matched to transfer RNAs, adding amino acids in sequence to build a polypeptide chain that later folds into a protein.

A three-nucleotide sequence in messenger RNA that specifies one amino acid or a stop signal. Sixty-four codons encode twenty amino acids plus three termination signals, making the code redundant.

A DNA region upstream of a gene where RNA polymerase and regulatory proteins assemble to start transcription. Its sequence and bound factors determine when and where a gene is expressed.

The removal of introns from a primary RNA transcript and joining of exons to form mature messenger RNA. Alternative splicing patterns let one gene produce several distinct protein variants.

One of the alternative versions of a gene at a given locus on a chromosome. Different alleles may produce different traits, and diploid organisms carry two copies of each locus.

The specific combination of alleles an individual carries at one or more loci. It interacts with the environment to produce the observable phenotype of the organism.

The observable traits of an organism, such as morphology, physiology, or behavior. It results from gene expression interacting with environmental conditions throughout development.

A relationship between alleles at one locus in which the phenotype of a heterozygote resembles the phenotype of one homozygote. It is a property of allele interactions, not of a gene alone.

The tendency of alleles at loci located close together on the same chromosome to be inherited together. Recombination between them occurs less often as physical distance decreases.

The exchange of DNA segments between homologous chromosomes during meiosis, producing new combinations of alleles. Its frequency between two loci estimates their genetic distance.

A null model in which allele and genotype frequencies in a population stay constant across generations when there is no mutation, migration, selection, drift, or nonrandom mating. Deviations indicate evolutionary forces acting.

An insertion or deletion of nucleotides whose number is not a multiple of three, shifting the reading frame downstream. The result is usually a truncated, nonfunctional protein.

A protein or RNA molecule that speeds up a biochemical reaction by lowering its activation energy. It binds substrates at an active site and is not consumed by the reaction.

A model describing reaction rate as a function of substrate concentration for a simple enzyme. The Michaelis constant Km approximates the substrate level giving half the maximum velocity.

Control of protein activity by a molecule binding at a site other than the active site, changing the protein's shape and function. It often produces sigmoidal kinetics and feedback control.

Reduction of enzyme activity by a molecule that blocks substrate binding or catalysis. Competitive inhibitors compete at the active site, while noncompetitive inhibitors bind elsewhere and lower maximum velocity.

A nonprotein ion or small organic molecule required by many enzymes for catalysis. Metal ions and coenzymes such as NAD+ assist reactions that the protein alone cannot perform.

The ten-step cytosolic pathway that converts glucose to pyruvate, producing ATP and NADH. It operates with or without oxygen and supplies carbon for many biosynthetic routes.

The mitochondrial process in which electrons from NADH and FADH2 pass through the electron transport chain, driving proton pumping and ATP synthesis by ATP synthase. Oxygen is the final electron acceptor.

Adenosine triphosphate, the cell's main energy currency. Hydrolysis of its terminal phosphate releases usable free energy that powers transport, biosynthesis, and mechanical work.

The maintenance of stable internal conditions, such as temperature, pH, and solute concentrations, despite fluctuations outside the organism. Negative feedback loops usually regulate these variables.

A regulatory loop in which the output of a process reduces the process itself, returning a variable toward a set point. It stabilizes physiological states and is common in endocrine and metabolic control.

The net movement of water across a selectively permeable membrane from lower to higher solute concentration. It drives water balance in cells, kidneys, and plant roots.

Differential survival and reproduction of individuals with heritable trait variants, leading to changes in trait frequencies across generations. It is a mechanism of evolution, not a goal-directed force.

Random change in allele frequencies between generations due to chance sampling of gametes, especially strong in small populations. It reduces genetic variation and can fix alleles without regard to fitness.

The relative contribution an individual's offspring make to the next generation's gene pool. It measures reproductive success in a given environment and drives evolutionary change.

The proportion of phenotypic variation in a population attributable to genetic variation. It applies to populations, not individuals, and depends on the range of environments examined.

The formation of new species through the accumulation of reproductive isolation between populations. It can occur with geographic separation or within the same area via polyploidy or disruptive selection.

A statement of no effect or no difference between groups, assumed true until evidence contradicts it. Statistical tests estimate the probability of observing the data if this hypothesis holds.

The probability of obtaining a test statistic at least as extreme as the observed one if the null hypothesis is true. It is not the probability that the null hypothesis is correct.

A range of values estimated from a sample that is expected to contain the true population parameter at a stated probability, usually ninety-five percent. Its width reflects precision.

A measure of the spread of data around the mean, equal to the square root of the variance. It is expressed in the same units as the original measurements.

The probability that a test will detect a real effect of a given size, equal to one minus the type II error rate. It rises with larger samples and lower measurement variability.

A study in which the researcher manipulates one variable while holding others constant, using a comparison group that does not receive the treatment. It supports causal inference.

A design feature in which participants, researchers, or both do not know which treatment was assigned. It reduces bias from expectations in measurement and reporting.

The repetition of an experiment or measurement, either within a study or by independent researchers. Replication estimates variability and strengthens confidence in the conclusions.

An in vitro method that repeatedly copies a target DNA sequence using primers, a thermostable polymerase, and temperature cycles. It amplifies small samples for detection, sequencing, or cloning.

A technique that separates DNA, RNA, or proteins by size and charge as they migrate through a gel under an electric field. It is used to visualize fragments and confirm amplification or digests.