Lecture Quiz on Chapters 10, 11, 12, and 14 Study Guide: Cell Division, Genetics, and Molecular Biology Study Guide

Comprehensive vocabulary flashcards covering cell reproduction, mitosis, meiosis, Mendelian genetics, inheritance patterns, and DNA structure, function, and replication for biology chapters 10, 11, 12, and 14.

Binary Fission

The asexual process of cell division in bacteria where a single cell replicates its circular DNA and divides into two nearly equal, clonal daughter cells.

Genome

The complete collection of genetic material in a cell or organism, residing in the nucleoid in prokaryotes and within the nucleus in eukaryotes.

Plasmid

A small, circular, extrachromosomal loop of double-stranded DNA in prokaryotes that carries accessory genes, such as those conferring antibiotic resistance, and can be transferred between bacteria.

Somatic Cells

Typical body cells of a multicellular organism that contain two complete, matched sets of chromosomes, classifying them as diploid ($2n$).

Gametes

Specialized reproductive cells (sperm and egg cells) containing half the chromosome number of somatic cells, making them haploid ($1n$).

Homologous Chromosomes

Matched chromosome pairs of the same length and centromere location that carry the same genes at corresponding loci, with one member inherited from each parent.

Autosomes

Non-sex chromosomes organized in homologous pairs, numbered $1$ through $22$ in humans for a total of $44$ autosomes ($22$ pairs).

Histones

Evolutionarily conserved octameric proteins around which eukaryotic DNA winds to form nucleosomes and facilitate chromatin packaging.

Nucleosome

The fundamental first level of eukaryotic DNA compaction, measuring approximately $10\,\text{nm}$ in diameter, where DNA wraps around eight core histone proteins to resemble beads-on-a-string.

Centromere

The constricted region of a chromosome containing repeated DNA sequences where sister chromatids are joined together by cohesin proteins.

Kinetochore

A specialized multiprotein structure assembled onto the centromeric region of each sister chromatid that binds to spindle microtubules during cell division.

$G_1$ Phase

The first gap phase of interphase where the cell is biochemically active, grows, and synthesizes necessary proteins and organelles prior to DNA synthesis.

$S$ Phase

The synthesis phase of interphase during which identical copies of nuclear DNA molecules are replicated to form sister chromatids joined at the centromere.

$G_2$ Phase

The second gap phase of interphase where energy stores are replenished, organelles duplicate, the cytoskeleton dismantles, and final preparations for mitosis occur.

$G_0$ Phase

A non-dividing, quiescent resting state outside the active cell cycle entered temporarily or permanently (as in cardiac and nerve cells) when conditions are not favorable for division.

Prophase

The initial mitotic stage wherein chromatin condenses into visible sister chromatids, the nucleolus disappears, the nuclear envelope begins breaking down, and centrosomes migrate toward opposite poles.

Prometaphase

The mitotic stage during which the nuclear envelope completely fragments and spindle microtubules attach to kinetochores located on sister chromatids.

Metaphase

The mitotic stage in which all chromosomes align along the equatorial plane (metaphase plate) between opposite spindle poles.

Anaphase

The mitotic stage in which cohesin proteins degrade, allowing sister chromatids to separate into individual daughter chromosomes pulled toward opposite centrosomes.

Telophase

The final stage of nuclear division where chromosomes reach the poles, decondense back into chromatin, nuclear envelopes re-form, and the mitotic spindle breaks down into tubulin monomers.

Cytokinesis

The physical separation of the cytoplasmic contents and organelles into two independent daughter cells, achieved via an actin cleavage furrow in animal cells and a cell plate in plant cells.

$G_1$ Checkpoint

The internal cell cycle checkpoint near the end of $G_1$ that evaluates cell size, nutrient reserves, growth signals, and genomic DNA integrity before committing to the $S$ phase.

$G_2$ Checkpoint

The regulatory transition point before mitosis that prevents entry into the $M$ phase if DNA replication is incomplete or if unresolved DNA damage is detected.

$M$ Checkpoint (Spindle Checkpoint)

The checkpoint occurring near the end of metaphase that ensures every kinetochore of all sister chromatids is securely attached to microtubules from opposite spindle poles before anaphase begins.

Cyclin-Dependent Kinases (Cdks)

Enzymatic serine/threonine protein kinases that phosphorylate target substrates to drive cell cycle progression, active only when bound to their corresponding cyclin partner.

Cyclins

Regulatory proteins whose intracellular concentrations oscillate predictably across different cell cycle stages, activating specific Cdks at distinct checkpoints.

Retinoblastoma Protein (Rb)

A negative regulatory protein that binds and inhibits E2F transcription factors to block $G_1 \rightarrow S$ transition until phosphorylated and inactivated.

$$p53$$

A tumor suppressor protein that monitors DNA integrity, halting the cell cycle to activate repair enzymes or initiating apoptosis when damage is irreparable.

Apoptosis

Genetically programmed cellular suicide triggered by regulatory mechanisms to eliminate severely damaged, mutated, or redundant cells without eliciting an inflammatory response.

Proto-oncogenes

Normal cellular genes encoding positive cell cycle regulators that, upon undergoing gain-of-function mutations, become oncogenes that stimulate uncontrolled proliferation.

Tumor Suppressor Genes

Genes encoding negative cell cycle regulatory proteins that halt aberrant division and maintain genomic integrity; loss-of-function mutations permit unrestrained division.

Diploid-Dominant Life Cycle

A sexual reproductive strategy typical of animals where the multicellular adult body is diploid ($2n$) and the only haploid ($1n$) cells produced are gametes.

Haploid-Dominant Life Cycle

A life cycle seen in most fungi and algae where the ecologically dominant multicellular stage is haploid ($1n$), and the diploid ($2n$) zygote immediately undergoes meiosis to produce haploid spores.

Alternation of Generations

A plant life cycle that alternates between a multicellular haploid gametophyte ($1n$) producing gametes and a multicellular diploid sporophyte ($2n$) producing spores via meiosis.

Synaptonemal Complex

A protein lattice that bridges homologous chromosomes along their lengths during prophase I of meiosis to stabilize them in synapsis.

Tetrad

The association of four chromatids formed by the tight pairing of two homologous chromosomes during prophase I of meiosis.

Crossing Over

The reciprocal exchange of genetic material between nonsister chromatids of homologous chromosomes during prophase I, generating recombinant chromosomes.

Chiasmata

Microscopically visible X-shaped junction points where non-sister chromatids have exchanged segments during crossing over, maintaining contact until anaphase I.

Independent Assortment

The random orientation and segregation of maternal and paternal homologous chromosome pairs along the equatorial plane during metaphase I of meiosis.

Nondisjunction

The abnormal failure of homologous chromosomes to segregate during meiosis I or sister chromatids to separate during meiosis II, resulting in aneuploid gametes.

Aneuploidy

A chromosomal condition wherein an individual or gamete carries an abnormal number of chromosomes deviating from the typical diploid count.

Monosomy

The loss of a single chromosome from a standard diploid complement, designated mathematically as $2n - 1$.

Trisomy

The presence of an extra third copy of a specific chromosome in a diploid organism, designated as $2n + 1$, exemplified by Trisomy $21$ (Down syndrome).

Cri-du-chat Syndrome

A human genetic disorder (also known as Lejeune's syndrome) caused by a partial deletion of the short arm of chromosome $5$.

Karyotype

An organized visual display or photographic arrangement (karyogram) of an individual's complete chromosome set, cataloged by size, banding pattern, and centromere position.

Gregor Johann Mendel

An Austrian Augustinian friar (1822–1884) recognized as the father of genetics for discovering the fundamental particulate laws of inheritance through experimental crosses of pea plants (Pisum sativum).

True-Breeding

Strains of organisms that are homozygous for given traits, consistently producing identical offspring with the same phenotype across successive generations when self-fertilized.

Allele

Specific, alternative nucleotide sequence variants of a single gene located at a particular chromosomal locus.

Homozygous

Genotypic condition in a diploid organism of possessing two identical alleles at a given gene locus (e.g., $PP$ or $pp$).

Heterozygous

Genotypic condition in a diploid organism of possessing two different alleles at a given gene locus (e.g., $Pp$).

Dominant Allele

An allele whose phenotypic effect masks the expression of an alternative allele when present in a heterozygous state.

Recessive Allele

An allele whose phenotypic expression is completely concealed in heterozygotes and is only visible when homozygous (e.g., $pp$).

Genotype

The specific underlying allelic composition or genetic makeup of an organism for a particular gene or set of genes.

Phenotype

The observable physical, biochemical, or physiological characteristics of an organism produced by the interaction of its genotype with the environment.

Law of Segregation (Mendel's First Law)

The genetic principle stating that the two alleles for a gene separate during gamete formation so that each gamete receives only one allele, restoring the pair upon fertilization.

Monohybrid Cross

A genetic mating cross between two parental organisms differing in only a single contrasting trait, yielding an $F_2$ phenotypic ratio of $3:1$ (dominant to recessive).

Test Cross

An experimental cross between an individual showing a dominant phenotype and a homozygous recessive individual to deduce whether the dominant parent is homozygous or heterozygous.

Law of Independent Assortment (Mendel's Second Law)

The genetic principle stating that alleles of distinct unlinked genes assort independently into gametes, yielding a characteristic $9:3:3:1$ $F_2$ phenotypic ratio in dihybrid crosses.

Product Rule (Multiplicative Law)

A probability theorem stating that the likelihood of two or more independent genetic outcomes occurring simultaneously equals the product of their individual probabilities ($P(A \text{ and } B) = P(A) \times P(B)$).

Sum Rule (Additive Law)

A probability theorem stating that the chance of any one of two or more mutually exclusive genetic events occurring equals the sum of their individual probabilities ($P(A \text{ or } B) = P(A) + P(B)$).

Pedigree

A genealogical diagram using standardized geometric symbols (squares for males, circles for females, shaded for affected) to chart the transmission of traits across familial generations.

Alkaptonuria

A rare autosomal recessive metabolic disorder of tyrosine and phenylalanine degradation that served historically as one of the first human conditions demonstrated to follow Mendelian recessive inheritance.

Incomplete Dominance

A non-Mendelian inheritance pattern where the heterozygous phenotype is an intermediate blend between both homozygous phenotypes, such as pink flowers in snapdragons resulting from red and white parents.

Codominance

A non-Mendelian inheritance pattern where both alleles in a heterozygote are simultaneously and fully expressed without blending, exemplified by human $AB$ blood type.

Polygenic Inheritance

An inheritance mode where multiple separate genes have an additive effect on the expression of a single continuous phenotypic trait, such as skin pigmentation or height.

Pleiotropy

A genetic condition in which a single mutant gene or allele causes multiple seemingly unrelated phenotypic effects or symptoms, as observed in sickle-cell anemia.

Epistasis

A gene interaction where the phenotypic expression of an allele at one gene locus is completely masked or altered by the presence of an allele at an entirely distinct locus.

Sex-Linked Trait

A phenotypic trait encoded by a gene residing on a sex chromosome, most commonly on the $X$ chromosome (such as hemophilia or red-green color blindness).

Friedrich Miescher

The Swiss physician who in 1869 first isolated a phosphate-rich acidic substance from the nuclei of leukocytes in surgical pus, which he named nuclein (later recognized as DNA).

Transforming Principle

The heritable agent identified by Frederick Griffith in 1928 that passed from heat-killed pathogenic $S$ strain Streptococcus pneumoniae to non-virulent $R$ strain bacteria, permanently transforming them into virulent capsules.

Avery, MacLeod, and McCarty Experiment

The 1944 biochemical investigation demonstrating that purified DNA from virulent bacteria, but not proteins degraded by proteases or RNA degraded by RNase, transformed benign cells, identifying DNA as the genetic material.

Hershey and Chase Experiment

The 1952 study using radioactive $^{32}\text{P}$ (labeling DNA) and $^{35}\text{S}$ (labeling protein) in $T2$ bacteriophages infecting E. coli that conclusively demonstrated viral DNA enters host cells to direct replication.

Bacteriophage

A virus consisting of a nucleic acid core encapsulated in a protein coat that exclusively infects and replicates inside bacterial cells.

Chargaff's Rules

The biochemical observation that in double-stranded DNA, the concentration of adenine equals thymine ($\%A = \%T$) and guanine equals cytosine ($\%G = \%C$).

Photo 51

The historic X-ray diffraction photograph of crystallized B-form DNA produced by Rosalind Franklin in 1952 that revealed DNA's helical dimensions and helical symmetry.

Watson and Crick Model

The 1953 structural model proposing that DNA is a double helix composed of two antiparallel polynucleotide strands held together by complementary base pairs on the interior.

Phosphodiester Bond

The covalent linkage between the $3'$ hydroxyl group of one deoxyribose sugar and the $5'$ phosphate group of the next nucleotide, forming the sugar-phosphate backbone of DNA.

Semiconservative Replication

The mechanism of DNA replication in which each original parent strand serves as a template, producing two daughter duplexes that each contain one parental strand and one newly synthesized strand.

Meselson and Stahl Experiment

The 1958 cesium chloride density gradient centrifugation experiment utilizing heavy ($^{15}\text{N}$) and light ($^{14}\text{N}$) isotopes in E. coli that confirmed DNA replicates semiconservatively.

DNA Helicase

An ATP-dependent enzyme that breaks hydrogen bonds between complementary base pairs to unwind and separate double-stranded DNA at the replication fork.

DNA Topoisomerase (DNA Gyrase)

An enzyme that introduces transient breaks in the DNA backbone to release torsional strain and prevent supercoiling ahead of the unwinding replication fork.

Primase

An RNA polymerase enzyme that synthesizes short RNA primers complementary to the template strand, providing the free $3'\text{-OH}$ group required by DNA polymerases.

DNA Polymerase III

The primary prokaryotic replication enzyme that adds complementary deoxynucleotides to the $3'$ end of a growing DNA strand in the $5' \rightarrow 3'$ direction.

DNA Polymerase I

The prokaryotic enzyme possessing $5' \rightarrow 3'$ exonuclease activity that excises RNA primers from Okazaki fragments and fills the resulting gaps with DNA nucleotides.

DNA Ligase

The enzyme that catalyzes the formation of covalent phosphodiester bonds to seal nicks in the sugar-phosphate backbone between adjacent Okazaki fragments.

Okazaki Fragments

Short, discontinuous segments of newly synthesized DNA generated on the lagging strand due to the directional constraint of synthesis away from the replication fork.

Telomeres

Repetitive, non-coding hexanucleotide sequences capping the linear ends of eukaryotic chromosomes that protect vital coding DNA from progressive loss during continuous replication.

Telomerase

A ribonucleoprotein reverse transcriptase enzyme carrying an internal RNA template that elongates the ends of linear chromosomes to prevent chromosome shortening in germ and stem cells.

Nucleotide Excision Repair

A DNA repair pathway wherein specialized nucleases recognize and excise bulky, helix-distorting DNA lesions, such as UV-induced thymine dimers, followed by resynthesis and ligation.

Mismatch Repair

A post-replication surveillance mechanism wherein repair enzymes identify, excise, and replace incorrectly paired bases that escaped the proofreading exonuclease activity of DNA polymerase.

Silent Mutation

A point mutation altering a codon nucleotide without changing the specified amino acid sequence due to genetic code degeneracy, yielding no functional change in the protein.

Missense Mutation

A single base-pair substitution that alters a codon to code for a different amino acid, which may alter protein conformation and function.

Nonsense Mutation

A point mutation that converts an amino-acid-specifying codon into a premature stop codon, leading to an abnormally truncated and typically non-functional polypeptide.

Frameshift Mutation

A genetic mutation caused by an insertion or deletion of nucleotides not divisible by three, permanently altering the reading frame of all downstream triplet codons during translation.