General Biology: Gene Regulation, Biotechnology, and Evolution

Comprehensive practice flashcards defining core terms in gene expression, biotechnology, population genetics, macroevolution, and molecular biology.

Gene Regulation

Mechanisms that turn on certain genes while other genes remain turned off, allowing cells with identical genetic instructions to differentiate and specialize in structure and function.

Gene Expression

The overall process by which genetic information flows from genes to functional proteins ($\text{DNA} \rightarrow \text{RNA} \rightarrow \text{protein}$).

Operon

A regulatory unit found in prokaryotes consisting of several related genes controlled by a single shared promoter and operator system.

Trp Operon

A bacterial operon containing five genes needed to synthesize the amino acid tryptophan; when tryptophan is present in sufficient amounts, it binds the repressor to turn off further synthesis.

Transcription Factors

A collection of regulatory proteins in eukaryotes that bind to DNA sequences (such as enhancers or silencers) and the promoter to control the binding of RNA polymerase and regulate transcription initiation.

Alternative RNA Splicing

An RNA processing mechanism in which exons can be spliced in different combinations from a single pre-mRNA, allowing an organism to produce multiple distinct polypeptides from a single gene.

microRNAs (miRNAs)

Small, single-stranded RNA molecules that bind to complementary sequences on target mRNA molecules in the cytoplasm to trigger their degradation or block their translation.

Oncogene

A cancer-causing gene that stimulates excessive and abnormal cell growth and division.

Proto-oncogene

A normal gene that has the potential to become an oncogene through mutation or altered gene expression.

Tumor-Suppressor Gene

A gene whose normal protein product inhibits cell division, thereby helping to prevent uncontrolled cell proliferation.

Biotechnology

The manipulation of living organisms or their components to produce useful products.

Genetically Modified Organism (GMO)

An organism that has acquired one or more genes by artificial means.

Transgenic Organism

A recombinant organism that has acquired a gene from an individual of another species.

Recombinant DNA

A DNA molecule formed by combining nucleotide sequences from two different sources—often different species—into a single molecule.

Restriction Enzymes

Bacterial enzymes that cut double-stranded DNA at specific recognition sequences called restriction sites.

Gel Electrophoresis

A laboratory technique used to separate macromolecules, such as DNA fragments or proteins, on the basis of their electrical charge and size.

DNA Profiling

The analysis of variable nucleotide sequences in the genome to determine whether biological samples originate from the same individual.

Plasmid

A small, circular DNA molecule that duplicates separately from the main bacterial chromosome and is widely used as a gene-cloning vector.

Humulin

Genetically engineered human insulin produced in $E.\,coli$ host cells, introduced in 1982 as the world's first genetically engineered pharmaceutical product.

Biological Species Concept

The definition of a species as a group of populations whose members have the potential to interbreed with one another in nature and produce viable, fertile offspring.

Prezygotic Barriers

Reproductive barriers that prevent mating or fertilization between species, consisting of temporal, habitat, behavioral, mechanical, and gametic isolation.

Postzygotic Barriers

Reproductive barriers that operate after hybrid zygotes form, including reduced hybrid viability, reduced hybrid fertility, and hybrid breakdown.

Allopatric Speciation

The formation of new species in populations that are geographically isolated from one another by a physical barrier.

Sympatric Speciation

The formation of new species in populations that live in the same geographic area without geographic isolation.

Polyploidy

A condition in which an organism possesses an extra set of chromosomes due to an accident during cell division, representing the ancestral origin of an estimated $80\%$ of present-day plant species.

Natural Selection

A process in which individuals with certain inherited traits are more likely to survive and reproduce than individuals with other traits, leading to evolutionary adaptation.

Evolutionary Fitness

The likelihood that a particular genetic variant or individual will survive and reproduce in a given environment.

Gene Pool

The total collection of all copies of every type of allele at every locus across all members of a population.

Hardy-Weinberg Equilibrium

The state of a nonevolving population wherein allele frequencies ($p$ and $q$) and genotype frequencies ($p^2$, $2pq$, and $q^2$) remain constant across generations.

Genetic Drift

A change in the gene pool of a population due to chance events, which can drive evolution without promoting adaptation.

Bottleneck Effect

A form of genetic drift resulting from a drastic reduction in population size that randomly decreases overall genetic variability and adaptability.

Founder Effect

A type of genetic drift that occurs when a small number of colonizing individuals establish a new, isolated population with a gene pool that differs randomly from the original population.

Gene Flow

The gain or loss of alleles from a population due to genetic exchange with another population, tending to reduce genetic differences between them.

Directional Selection

A mode of natural selection that shifts the overall phenotypic makeup of a population by favoring individuals at one extreme of the distribution.

Disruptive Selection

A mode of natural selection that favors individuals at both ends of the phenotypic range over individuals with intermediate phenotypes.

Stabilizing Selection

The most common mode of natural selection, which favors intermediate phenotypes and acts against extreme variants in relatively stable environments.

Sexual Dimorphism

A distinction in secondary sexual characteristics and appearance between males and females of the same species.

Taxonomy

The branch of biology concerned with identifying, naming, and classifying species.

Binomial

The two-part Latinized scientific name of a species, consisting of the capitalized genus name followed by the specific epithet, both printed in italics.

Homologous Structures

Anatomical features in different species that vary in form and function but exhibit fundamental underlying similarities inherited from a common ancestor.

Vestigial Structures

Rudimentary remnants of structures that had important functions in an organism's evolutionary ancestors but serve little or no current purpose.

Analogy

Superficial similarity between organisms from different evolutionary branches resulting from convergent evolution rather than common descent.

Exaptation

A structure that originally evolved in one selective context and was later co-opted for a novel function.

Archaeopteryx

An early fossil organism representing a transitional form between dinosaurs and birds, exhibiting reptilian teeth, forelimb claws, and a bony tail alongside avian flight feathers.

Transcription

The transfer of genetic information from a DNA template strand into an RNA molecule, catalyzed by RNA polymerase.

Translation

The transfer of genetic information from mRNA codons into a sequence of amino acids to form a polypeptide strand.

Codon

A three-base nucleotide sequence in DNA or mRNA that codes for a specific amino acid or acts as a polypeptide termination signal.

Promoter

A specific nucleotide sequence located on DNA at the beginning of a gene that provides the attachment site for RNA polymerase to initiate transcription.

Introns

Internal noncoding regions of RNA transcripts that are removed before the mRNA exits the nucleus.

Exons

The expressed, coding regions of a gene that remain after splicing to form the mature mRNA sequence.

Spliceosome

A complex composed of proteins and small RNA molecules that mediates RNA splicing by excising introns and joining exons.

Transfer RNA (tRNA)

A specialized RNA molecular interpreter that carries a specific amino acid and pairs its anticodon with the complementary codon on mRNA during translation.

Anticodon

A specific base triplet located at one end of a tRNA molecule that base-pairs with a complementary mRNA codon.

Ribosome

A cytoplasmic organelle consisting of a large and small subunit made of proteins and ribosomal RNA (rRNA) that coordinates the translation of mRNA into polypeptides.

Missense Mutation

A base substitution that alters a single codon, causing the insertion of a different amino acid into the polypeptide.

Nonsense Mutation

A base substitution mutation that converts an amino acid codon into a stop codon, prematurely terminating polypeptide synthesis.

Frameshift Mutation

A mutation resulting from the deletion or insertion of one or more nucleotides not in multiples of three, altering the triplet reading frame and typically producing a nonfunctional polypeptide.