Bio 1210 Exam 3 Master Study Guide: Cellular Reproduction, Genetics, and Molecular Biology

Comprehensive practice flashcards covering cellular reproduction, Mendelian genetics, non-Mendelian inheritance, molecular DNA architecture, replication fork mechanics, gene expression, and mutations for Bio 1210 Exam 3.

Gene

A fundamental physical and functional unit of heredity associated with a specific biological character.

Locus

The precise, physical location or coordinate that a specific gene occupies on a chromosome (plural: Loci).

Allele

Alternative nucleotide sequence versions of the same gene that arise by mutation and are found at the same locus.

Trait

A particular, identifiable form of a physical or physiological character (e.g., round vs. wrinkled seeds).

Genotype

The exact allelic composition or genetic combination that an organism carries at a specific locus.

Phenotype

The physically observable, measurable, or biochemical trait produced by the interaction of the genotype and environment.

Homozygous

Possessing two identical alleles at a given locus on homologous chromosomes (e.g., $GG$ or $gg$).

Heterozygous

Possessing two distinctly different alleles at a given locus on homologous chromosomes (e.g., $Gg$).

Dominant Allele

An allele that completely masks or conceals the phenotypic presence of a recessive allele in a heterozygote.

Recessive Allele

An allele whose phenotypic expression is entirely hidden or masked by a dominant allele in a heterozygous state.

Homologous Chromosomes

A matched physical pair of chromosomes (one maternal, one paternal) carrying genes for the same characters at identical loci.

Sister Chromatids

Two identical, duplicated copies of a single chromosome produced during DNA synthesis, joined firmly at a centromere.

Autosomes

Chromosomes that are not directly involved in determining the biological sex of an organism (human chromosome pairs 1–22).

Sex Chromosomes

The final pair of chromosomes ($23^{\text{rd}}$ pair in humans) that dictate genetic sex determination (typically $XX$ or $XY$).

Diploid ($2n$)

A cellular state containing two complete homologous sets of chromosomes, one set inherited from each parent.

Haploid ($n$)

A cellular state containing only a single complete set of chromosomes, characteristic of mature gametes.

Euploid

A cellular state featuring an exact, normal integer multiple of a basic chromosome set (includes both normal haploid and diploid states).

Transmit Hereditary Information

A primary biological imperative of cellular division to ensure faithful replication and distribution of DNA to new cellular lineages.

Support Growth and Development

A primary biological imperative of cellular division enabling a single-celled zygote to proliferate into a complex multicellular organism.

Repair Tissues

A primary biological imperative of cellular division to replace damaged, old, or senescent cells within tissues to maintain homeostatic structural integrity.

Chapter 7 Exam Blueprint Scope

Covers questions 1–17 on Mitosis, Meiosis, the Cell Cycle, Gametogenesis, and Chromosomal Errors.

Chapter 8 Exam Blueprint Scope

Covers questions 18–35 on Mendelian Genetics, Crosses, Extensions (Incomplete Dominance, Codominance, Epistasis, Pleiotropy, Polygenic Traits), Pedigree Charts, and Sex-Linked Traits.

Chapter 9 Exam Blueprint Scope

Covers questions 36–47 on DNA Architecture, Historical Experiments, Semiconservative Replication Fork Mechanics, mRNA Translation/Codon Tracking, and PCR Biotechnology.

Chapter 10 Exam Blueprint Scope

Covers Gene Expression, Transcription, mRNA Processing, Translation, and Mutations.

Prokaryotic Chromosome Structure

A single circular DNA molecule located in the cytoplasm without enclosure in a membrane-bound nucleus.

Binary Fission

The rapid asexual division process through which prokaryotes (bacteria and archaea) replicate their circular chromosome and split into two identical cells.

Replication Origin ($ori$)

The specific nucleotide locus on a circular bacterial chromosome where DNA replication initiates.

Replication Terminus ($ter$)

The specific nucleotide locus on a circular bacterial chromosome where bidirectional replication terminates.

Environmental Control of Bacterial Division

The biological response where abundant food supplies significantly accelerate the rate of the bacterial binary fission cycle.

Horizontal Gene Transfer (HGT)

Non-reproductive lateral transfer pathways that introduce genetic variation into clonal prokaryotic populations.

Transformation

The direct bacterial uptake and genomic integration of foreign exogenous DNA fragments from the surrounding extracellular environment.

Conjugation

The direct physical transfer of genetic material between two bacterial cells via a specialized cytoplasmic bridge called a pilus.

Pilus

A specialized cytoplasmic bridge that physically connects two bacterial cells to facilitate conjugation.

Plasmids

Small, circular, extra-chromosomal double-stranded DNA rings that replicate independently of the bacterial chromosome and frequently carry antibiotic resistance genes.

Eukaryotic DNA Compaction Hierarchy

Double-Stranded DNA Helix $\rightarrow$ Nucleosomes (DNA wrapped around histones) $\rightarrow$ Chromatin Fiber $\rightarrow$ Condensed Chromosomes.

Nucleosome

The fundamental subunit of eukaryotic chromatin packaging, consisting of double-stranded DNA wrapped around a core of histone proteins.

Histones

Specialized basic proteins around which linear eukaryotic double-stranded DNA winds to form nucleosome complexes.

Chromatin Fiber

An intermediate structural packaging level formed by closely stacked and coiled arrays of nucleosomes.

Condensed Chromosomes

The highly compacted, physically discrete state that linear eukaryotic chromatin assumes prior to active nuclear division.

Interphase Chromatin State

The accessible, uncoiled structural configuration of DNA maintained throughout interphase to permit ongoing transcription and replication.

Cell Cycle

The ordered sequence of events oscillating between a prolonged preparatory phase (interphase) and a brief division phase (M phase).

Interphase

The cell cycle phase where the cell grows, synthesizes metabolic enzymes and organelles, and replicates its nuclear DNA; comprises $G_1$, $S$, and $G_2$.

$G_1$ Phase (First Gap)

The longest and most variable subphase of interphase, during which the cell grows larger, synthesizes metabolic enzymes, duplicates organelles (ribosomes), and undergoes intense protein production.

$G_0$ Phase (Resting)

A non-dividing, metabolically active state entered from $G_1$ by specialized cells that do not proliferate.

Mature Neurons ($G_0$)

An example of highly specialized human cells that exit the cell cycle into a permanent $G_0$ resting state and do not undergo division.

$S$ Phase (Synthesis)

The subphase of interphase where the cell synthesizes a complete copy of nuclear DNA, maintaining chromosome count while doubling chromatids into attached sister pairs.

Centromere

The constricted chromosomal region where two duplicated sister chromatids are held firmly together.

$G_2$ Phase (Second Gap)

The final subphase of interphase where the cell undergoes final growth, synthesizes specialized proteins like tubulin, and reorganizes contents for mitosis.

Tubulin

A specialized structural protein actively produced during the $G_2$ phase that polymerizes to construct mitotic spindle microtubules.

M Phase

The overarching cell cycle division phase responsible for nuclear division (mitosis) and cytoplasmic splitting (cytokinesis).

Prophase

The mitotic subphase where chromatin tightly condenses into distinct chromosomes, the nucleolus disappears, and the mitotic spindle begins assembling from separating centrosomes.

Nucleolus Disappearance

The dissolution of the ribosome-synthesizing nuclear region that takes place during prophase.

Mitotic Spindle

A dynamic cytoskeletal apparatus of microtubules assembled from separating centrosomes that physically coordinates chromosome movement.

Centrosome

The microtubule-organizing center of animal cells that separates to opposite cell poles during prophase to anchor the mitotic spindle.

Prometaphase

The subphase where the nuclear envelope breaks down into membrane vesicles and spindle microtubules invade the nuclear region to bind kinetochores on centromeres.

Nuclear Envelope Breakdown

The disintegration of the nuclear membrane into vesicles during prometaphase, granting spindle microtubules physical access to condensed chromosomes.

Membrane Vesicles (Mitosis)

The fragmented structural remnants of the dismantled nuclear envelope produced during prometaphase.

Kinetochores

Protein complexes assembled at the centromere of each chromosome that serve as binding sites for spindle microtubules during prometaphase.

Metaphase

The subphase where microtubules pull and push chromosomes until they align single-file along the equatorial metaphase plate.

Metaphase Plate

The imaginary equatorial plane midway between the spindle poles where chromosomes align in a single row during metaphase.

Cell Cycle Subphase Table (Interphase to Metaphase)

A summary chart detailing the mechanistic and physical actions of $G_1$, $G_0$, $S$, $G_2$, Prophase, Prometaphase, and Metaphase.

Anaphase

The mitotic subphase where motor proteins shorten spindle fibers, tearing sister chromatids apart at their shared centromere into individual daughter chromosomes.

Motor Proteins (Mitosis)

Molecular motors that actively shorten spindle fibers during anaphase, pulling separated chromatids toward opposite cellular poles.

Daughter Chromosomes

The official designation for sister chromatids once they physically separate at their centromere during anaphase.

Telophase

The subphase where chromosomes arrive at opposite poles, uncoil into loose chromatin, and nuclear envelopes and nucleoli re-form around two distinct nuclei.

Chromatin Uncoiling

The relaxation of highly condensed chromosomes back into diffuse, accessible chromatin during telophase.

Cytokinesis

The physical division of the parental cell cytoplasm into two individual daughter cells following mitosis.

Animal Cell Cytokinesis

Cytoplasmic division driven by an actin-myosin contractile ring pinching the plasma membrane inward from the outside to form a cleavage furrow.

Actin-Myosin Contractile Ring

A ring of cytoskeletal microfilaments that constricts the plasma membrane inward during animal cell cytokinesis.

Cleavage Furrow

The indentation or groove formed at the equator of an animal cell as the actin-myosin ring pinches inward.

Plant Cell Cytokinesis

Cytoplasmic division where internal vesicles fuse to form a rigid cell plate that expands outward from the inside to construct a new cell wall.

Cell Plate

A rigid membrane-bound structure formed by coalescing vesicles in dividing plant cells that grows outward to form a new cell wall.

Cell Cycle Subphase Table (Anaphase to Cytokinesis)

A reference table outlining the mechanistic and physical cellular actions of Anaphase, Telophase, and Cytokinesis in animal and plant cells.

PMAT Mnemonic

A memory tip ('Please Meet At Telophase') representing the sequential subphases of mitosis: Prophase, Metaphase, Anaphase, Telophase.

Cell Cycle Checkpoints

Surveillance control points within the eukaryotic cell cycle that verify critical cellular criteria and halt progression if defects or damages are detected.

Tumors

Localized cellular masses that form when cell cycle checkpoint controls fail and cells divide in an unchecked, rapid manner.

Cancer

Clinical malignancies that develop when cell cycle checkpoints fail entirely, causing unregulated, invasive cellular proliferation.

$G_1$ Checkpoint

A regulatory checkpoint that assesses whether cell size is adequate, energy reserves are sufficient, and the genomic template DNA is undamaged.

$G_2$ Checkpoint

A regulatory checkpoint that verifies whether nuclear DNA replication during the $S$ phase was completely and accurately executed without copying errors.

Spindle (M) Checkpoint

A regulatory checkpoint during metaphase that senses mechanical tension to confirm all kinetochores are securely bound to spindle microtubules before allowing anaphase.

Kinetochore Tension

The mechanical signal detected by the M checkpoint indicating proper bipolar microtubule attachment across all aligned chromosomes.

Apoptosis

A pathway of programmed cell death activated when cellular machinery fails to repair genomic damage detected at checkpoints.

Metaphase Chromosome Count (24-Chromosome Cell)

A parent cell with 24 chromosomes in $G_1$ maintains exactly 24 duplicated chromosomes at mitotic metaphase.

Metaphase Sister Chromatid Count (24-Chromosome Cell)

A parent cell with 24 chromosomes in $G_1$ possesses exactly 48 sister chromatids aligned at the metaphase plate prior to anaphase separation.

Cytokinesis Directionality Comparison

Animal cells divide from the outside in via membrane pinching; plant cells divide from the inside out via internal cell plate synthesis.

Taxol

A chemotherapy drug that stabilizes spindle microtubules, preventing them from shortening and arresting dividing cancer cells at the M checkpoint to trigger apoptosis.

Microtubule Stabilization

The pharmacological mechanism of Taxol that prevents microtubule depolymerization, blocking sister chromatid separation during anaphase.

Mitosis Division Count & Output

Consists of 1 nuclear division and 1 cell division, generating 2 genetically identical diploid ($2n$) somatic daughter cells.

Somatic Cells

Non-reproductive body cells that divide by mitosis to form, maintain, and repair multicellular tissues.

Evolutionary Purpose of Meiosis

To generate genetically unique haploid ($n$) gametes from diploid ($2n$) germline cells, ensuring chromosome numbers do not double upon fertilization.

Gametes

Mature haploid sex cells (sperm or egg) produced by meiosis that fuse during sexual reproduction.

Germline Cells

Specialized diploid ($2n$) precursor cells set aside within reproductive organs that undergo meiosis to produce gametes.

Meiosis Division Count & Output

Consists of 1 round of DNA replication followed by 2 distinct division rounds (Meiosis I and Meiosis II), producing 4 genetically distinct haploid ($n$) gametes.

Meiosis I (Reductional Division)

The first meiotic division round that separates homologous chromosome pairs, reducing cellular ploidy from diploid ($2n$) to haploid ($n$).

Synapsis

The tight physical pairing and side-by-side alignment of homologous chromosomes occurring during Prophase I of meiosis.

Tetrad

The four-chromatid structure formed by a synapsed pair of homologous chromosomes during Prophase I.

Chiasmata

The X-shaped physical contact points where non-sister chromatids break and exchange genetic segments during crossing over.

Crossing Over

The breakage and reciprocal swapping of corresponding physical segments between non-sister homologous chromatids during Prophase I.

Recombinant Chromosomes

Novel chromosomes produced by crossing over that carry shuffled combinations of maternal and paternal alleles.

Metaphase I

The meiotic stage where homologous pairs align side-by-side in two parallel rows along the metaphase plate.