Cellular Genetics, Inheritance, Biotechnology, and Evolution

Comprehensive vocabulary flashcards covering the molecular structure and function of DNA and RNA, protein synthesis, gene expression, inheritance mechanisms, biotechnology applications, and evolutionary processes.

Genetics

The study of heredity.

Heredity

The transfer of biological characteristics from one generation to the next.

Inheritance

A principle of genetics that explains how characteristics are transferred from one generation to the next based on the passage of DNA.

DNA (Deoxyribonucleic Acid)

A double-stranded helical molecule composed of nucleotide chains that stores genetic information and dictates cellular processes such as protein synthesis.

Nucleotide

The fundamental building block of nucleic acids, consisting of a phosphate group, a five-carbon sugar, and a nitrogenous base.

Gene

A specific sequence of bases in DNA that codes for the production of a particular protein or RNA molecule.

Genome

An organism's complete set of genetic material, containing approximately $20{,}000$ genes in humans.

Chromatin

A thin, thread-like complex of DNA and protein found during interphase that facilitates gene transcription.

Chromosome

A compact, tightly-wound structure of condensed DNA wrapped around histone proteins, assembled to facilitate safe manipulation and distribution during cell division.

Locus

The fixed physical position of a gene on a chromosome.

Allele

A variant or alternative form of a specific gene.

Homologous Chromosomes

A pair of matching chromosomes (one maternal and one paternal) that possess the same gene loci and determine the same genetic traits.

Telomeres

Repetitive, non-coding regions of structural DNA located at the ends of linear chromosomes that act as protective caps preventing the loss of vital coding DNA during cell division.

Centromere

A region of structural DNA made of simple sequence repeats where proteins bind to attach spindle fibres during cell division, allowing chromatids to be pulled to opposite poles.

DNA Helicase

An enzyme that unzips the DNA double helix during replication by breaking hydrogen bonds between complementary base pairs to produce single template strands.

DNA Polymerase

An enzyme that synthesizes new DNA strands by pairing free nucleotides with exposed template bases and building the stable sugar-phosphate backbone.

Okazaki Fragments

Short segments of DNA synthesized discontinuously in the $5'$ to $3'$ direction by DNA polymerase along the lagging ($3' \rightarrow 5'$) strand.

Independent Assortment

The independent alignment and arrangement of homologous chromosome pairs along the cell equator during meiosis.

Random Segregation

The random separation and distribution of chromosomes/chromatids into daughter cells during meiotic division.

Crossing Over

The exchange of genetic material between non-sister chromatids of homologous chromosomes during meiosis, creating new allelic combinations.

Spermatogenesis

The continuous process of male gamete formation in the seminiferous tubules of the testes from puberty onwards, producing four functional haploid spermatozoa from one diploid cell.

Oogenesis

The discontinuous process of female gamete formation that commences in the ovaries during foetal development, pauses at prophase I, resumes at puberty, and produces one large haploid ovum and two to three polar bodies.

Mutagen

Any physical, chemical, or biological agent capable of altering the molecular structure of DNA and causing mutations.

Point Mutation

A gene mutation that involves a change in only a single nucleotide base within a DNA sequence, primarily caused by errors during replication.

Frameshift Mutation

A mutation caused by the insertion or deletion of one or more nucleotides, shifting the triplet reading frame and altering every downstream codon.

Missense Mutation

A single-base substitution where the altered codon results in the incorporation of a different amino acid in the synthesized polypeptide.

Nonsense Mutation

A single-base substitution that creates a premature stop codon, terminating polypeptide chain elongation early.

Silent Mutation

A single-base substitution that codes for the same amino acid due to degeneracy of the genetic code, resulting in an unaltered protein.

Chromosomal Mutation

Any large-scale structural change in a chromosome or change in chromosome number, such as deletion, inversion, translocation, duplication, or non-disjunction.

Non-Disjunction

An error during cell division where homologous chromosome pairs or sister chromatids fail to separate correctly, leading to aneuploidy in daughter cells.

Aneuploidy

A chromosomal condition in which a cell has an abnormal number of copies of a specific chromosome (e.g., trisomy $21$ in Down syndrome or XXY in Klinefelter syndrome).

Polyploidy

A genetic condition in which an organism acquires one or more complete extra sets of chromosomes (common in plants; lethal in humans).

Promoter Region

A non-coding DNA sequence located upstream at the $5'$ end of a gene's template strand that instructs RNA polymerase where to bind to begin transcription.

Exons

Coding nucleotide sequences of a gene that are retained in mature mRNA and translated into amino acids.

Introns

Non-coding sequences of DNA located between exons that are removed from pre-mRNA by the spliceosome before translation.

Transcription

The nuclear process where RNA polymerase uses a gene's DNA strand as a template to synthesize a complementary single-stranded messenger RNA (mRNA) molecule.

Translation

The cellular process occurring at ribosomes where the codon sequence of an mRNA molecule is decoded by tRNAs to synthesize a specific polypeptide chain.

Structural Genes

Genes that code for proteins or functional RNAs not directly involved in regulating other genes (e.g., metabolic enzymes).

Regulatory Genes

Genes that produce RNA or protein products that function to control the transcription or translation of other genes.

Constitutive Genes

Housekeeping genes that are continually expressed and transcribed in a particular cell under normal conditions.

Transcription Factors

Regulatory proteins that bind to specific DNA sequences to mediate and control the interaction between RNA polymerase and DNA, altering transcription levels.

HOX Genes

A family of master regulatory genes that code for transcription factors that control morphology and anatomical structure formation during embryonic development.

Epigenetics

The study of stable, heritable changes in phenotype or gene expression that occur without altering the underlying nucleotide sequence of DNA.

Genotype

The specific genetic makeup or combination of alleles present in an organism's DNA for a particular trait.

Phenotype

The observable physical or physiological traits and characteristics of an organism resulting from gene expression and environmental interactions.

Co-Dominance

An inheritance pattern in which both alleles in a heterozygote are fully and distinctly expressed in the phenotype simultaneously (e.g., roan cattle, AB blood group).

Incomplete Dominance

An inheritance pattern in which the dominant allele is only partially expressed over the recessive allele, yielding an intermediate phenotype in heterozygotes (e.g., pink snapdragons).

Polygenic Inheritance

The inheritance of a phenotypic trait determined by the additive effects of multiple independent genes, producing continuous variation across a spectrum (e.g., human skin colour, height).

Sex-Linked Inheritance

The transmission of genetic traits coded for by genes located on sex chromosomes ($X$ or $Y$), often resulting in different phenotypic distributions between sexes.

Recombinant DNA

A DNA molecule engineered in vitro by joining genetic material isolated from two or more different biological organisms or sources.

Restriction Enzymes

Endonuclease enzymes that recognize and cleave specific target DNA sequences, producing complementary single-stranded overhanging sticky ends.

DNA Ligase

An enzyme that catalyses the joining of DNA fragments by reforming phosphodiester bonds within the sugar-phosphate backbone.

Bacterial Transformation

The biotechnology process whereby bacterial cells are induced to take up exogenous foreign DNA (such as recombinant plasmids) from their environment using calcium ions and heat shock.

Polymerase Chain Reaction (PCR)

An in vitro technique that exponentially amplifies a specific target region of DNA through repetitive thermal cycles consisting of denaturation ($95^\circ\text{C}$), primer annealing ($55^\circ\text{C}$), and enzymatic extension ($72^\circ\text{C}$).

Gel Electrophoresis

A laboratory technique used to separate and visualise negatively charged DNA fragments according to molecular size as they migrate through an agarose matrix toward the positive electrode under an electric current.

DNA Profiling

The analysis of variable non-coding regions containing short tandem repeats (STRs) to generate a unique banding pattern used for personal identification or parentage testing.

DNA Sequencing

The biochemical process of determining the exact sequence of nucleotide bases ($\text{A, T, C, G}$) across a specific gene or an entire genome (e.g., using Sanger chain-terminating dideoxynucleotides).

Microevolution

Small-scale changes in allele frequencies within the gene pool of a population across successive generations, producing descendants that remain within the same taxonomic group.

Macroevolution

Major, large-scale evolutionary change resulting from the accumulation of microevolutionary events over geological time, operating at or above the species level and leading to speciation.

Gene Pool

The dynamic total collection of all alleles for all genes present within an interbreeding population at a given time.

Gene Flow

The movement and incorporation of alleles between different populations due to the migration and interbreeding of fertile individuals.

Genetic Drift

Random, chance events (such as accidental deaths or births) that cause unpredictable fluctuations in allele frequencies within a population, having the greatest effect in small populations.

Selection Pressures

External biotic or abiotic environmental factors that influence an organism's survival, reproductive output, and behavior based on its phenotype.

Stabilising Selection

A form of natural selection where intermediate phenotypes around the population mean are favoured, while extreme phenotypic variations are selected against in a stable environment.

Directional Selection

A form of natural selection that favours individuals exhibiting one extreme phenotype over the mean and opposite extreme, causing the distribution curve to shift toward that extreme in a changing environment.

Disruptive Selection

A form of natural selection occurring in varied environments that favours individuals at both phenotypic extremes while selecting against intermediate/mean phenotypes, resulting in a bimodal curve.

Speciation

The evolutionary formation of new and distinct biological species resulting from reproductive isolation and diverging gene pools.

Allopatric Speciation

Speciation that occurs when populations of a species become geographically separated by physical barriers (such as oceans or mountains) that prevent gene flow.

Sympatric Speciation

Speciation that occurs within populations occupying the same geographic habitat, driven by reproductive barriers such as behavioural or temporal differences.

Parapatric Speciation

Speciation occurring when organisms occupy the same continuous area but mate predominantly with geographically close individuals across an environmental gradient.

Divergent Evolution

An evolutionary pattern in which two or more related species descend from a common ancestor and develop different characteristics due to exposure to distinct selection pressures.

Convergent Evolution

The independent development of analogous structures and similar adaptations in distantly related species resulting from exposure to similar environmental selection pressures (e.g., sharks and dolphins).

Coevolution

The reciprocal evolutionary change in two or more interacting species where the adaptations of one exert direct selection pressure on the survival of the other (e.g., predator-prey relationships).

Phylogenetic Tree

A branching diagram that illustrates inferred evolutionary relationships, common ancestry, and divergence events among biological taxa based on genomic, morphological, and fossil data.

Comparative Genomics

A biological discipline that compares the complete genomic sequences of different organisms to determine sequence homology, evolutionary relatedness, and divergence times.

Bottleneck Effect

A severe reduction in population size and genetic diversity caused by environmental catastrophes or disease, leaving a surviving population with an unrepresentative gene pool.

Mass Extinction

A catastrophic event characterized by the rapid loss of a large percentage of Earth's species across multiple taxonomic groups within a geologically brief interval (e.g., $75\%\text{--}76\%$ loss at the End-Cretaceous).

Evolutionary Radiation

A rapid increase in taxonomic diversity and morphological disparity within a clade caused by elevated rates of speciation, commonly following mass extinction events or entry into unoccupied ecological niches.