Biology Test 4 Review: Cell Signaling, the Cell Cycle, Mitosis, Meiosis, and Mendelian Genetics

Vocabulary practice flashcards covering cell signaling pathways, apoptosis, the stages of the cell cycle and mitosis, meiosis, chromosome terminology, and Mendelian inheritance principles.

Paracrine Signaling

A type of local cell signaling where cells communicate over short distances without directly touching.

Direct Signaling

Local cell communication that occurs through direct physical contact and cell-to-cell recognition.

Endocrine Signaling

Long-distance signaling in which hormones travel to target cells throughout the body.

Synaptic Signaling

A specialized type of local communication involving nerve signals and neurotransmitters.

Receptor Tyrosine Kinase

A plasma membrane receptor that undergoes self-phosphorylation upon activation.

G Protein-Coupled Receptor

A plasma membrane receptor that functions by interacting with an associated G protein.

Hormone-Receptor Complex

An intracellular receptor system that bypasses the transduction cascade to initiate a cellular response directly.

Protein Kinase

An enzyme that phosphorylates target molecules by adding a phosphate group.

Protein Phosphatase

An enzyme that dephosphorylates target molecules by removing a phosphate group.

Phosphorylation Cascade

A series of sequential signaling events where one kinase activates another kinase until a phosphatase deactivates the pathway by removing a phosphate group.

Secondary Messenger

A non-protein molecule involved in signal transduction, with cyclic AMP and calcium ions being the most common examples.

Scaffolding Protein

A protein that physically holds multiple kinases together to accelerate and enhance cellular signaling processes.

Apoptosis

Programmed cell suicide triggered by either internal damage signals or external signals commanding the cell to die.

Ligand-Gated Ion Channel

A membrane channel receptor that opens to permit the rapid influx of specific ions into the cell upon binding a signaling molecule.

Acetylcholine

A neurotransmitter released during synaptic signaling that triggers ligand-gated ion channels to open, allowing sodium ions to flood in and induce muscle contraction.

Gametes

Haploid reproductive sex cells (eggs and sperm) produced in the ovaries or testes via meiosis.

Somatic Cells

All diploid body cells containing a complete set of chromosomes, excluding gametes.

Sister Chromatids

Identical duplicated copies of a chromosome synthesized during S phase and held together at the centromere.

$G_1$ Phase

The first growth phase of interphase where cells carry out their normal functions and where non-dividing cells remain.

S Phase

The synthesis phase of interphase during which DNA replication occurs, duplicating all $46$ chromosomes.

$G_2$ Phase

The second growth phase of interphase and final stage before mitosis, during which centrosomes are duplicated.

Prophase

The first stage of mitosis, characterized by chromatin condensing into visible chromosomes, nucleoli disappearing, and centrosomes initiating mitotic spindle formation.

Prometaphase

The stage of mitosis where chromosomes condense further, nucleoli fully break down, and spindle microtubules attach to kinetochores.

Metaphase

The mitotic stage where chromosomes align along the center of the cell to form the metaphase plate and the spindle is completely assembled.

Anaphase

The stage of mitosis where sister chromatids are pulled apart toward opposite centrosomes by kinetochore microtubules while non-kinetochore microtubules elongate the cell.

Telophase

The mitotic stage that reverses prophase and prometaphase by reforming nuclear envelopes, restoring nucleoli, decondensing chromosomes, and dismantling the mitotic spindle.

Cytokinesis

The division of the cytoplasm via a cleavage furrow following mitosis; failure of this process results in a multinucleated cell.

Mitotic Spindle

A temporary cellular structure composed of microtubules originating from centrosomes that functions solely to assemble and separate chromosomes before disassembling.

Centrosome

An organelle consisting of a pair of centrioles that duplicates in $G_2$ and organizes kinetochore, non-kinetochore, and aster microtubules.

Kinetochore

A protein structure located at the centromere of each chromosome where spindle microtubules attach.

Cyclin-Dependent Kinases (CDKs)

Molecules that phosphorylate target proteins to advance the cell through cycle checkpoints, remaining dormant until activated by binding cyclin.

Cell Cycle Checkpoints

Regulatory stop-and-go gates ($G_1$, $G_2$, and $M$) ensuring only healthy cells with undamaged, accurately replicated, and properly attached chromosomes proceed with division.

Locus

The specific physical location of a gene on a chromosome.

Autosomes

The $22$ pairs of non-sex chromosomes that code for somatic body characteristics in humans.

Homologous Pair

Matching pairs of maternal and paternal chromosomes carrying genes for the same traits that pair up during meiosis.

Crossing Over

The exchange of genetic material between homologous maternal and paternal chromosomes during prophase I of meiosis, creating new allele combinations and genetic diversity.

Independent Assortment

The random orientation and segregation of maternal and paternal chromosome pairs during meiosis, giving a $50/50$ probability of inheriting either chromosome.

Allele

Alternative versions of a gene characterized by differing sequences of DNA nucleotides.

Law of Segregation

Mendel's genetic rule stating that the two alleles for a trait separate randomly during gamete formation so that each gamete carries only one allele.

Codominance

A pattern of inheritance where two different alleles for a gene are simultaneously expressed, showing both individual phenotypes.

Incomplete Dominance

A genetic condition where neither allele is fully dominant, resulting in a blended intermediate phenotype.

Homozygous

Having two identical alleles for a given gene (e.g., $BB$ or $bb$).

Heterozygous

Having two different alleles for a given gene (e.g., $Bb$).

Phenotype

The observable physical characteristics and traits of an organism.

Genotype

The genetic makeup or specific allele composition of an organism.

Testcross

Breeding an individual showing a dominant phenotype with a homozygous recessive individual to determine the dominant individual's unknown genotype.

Huntington's Disease

A lethal dominant genetic disorder that remains prevalent in populations because its phenotypic effects do not emerge until ages $35\text{--}45$.

Polygenic Inheritance

An inheritance mechanism where multiple distinct genes influence a single quantitative phenotypic characteristic.

Epistasis

A genetic phenomenon in which one gene masks or overrides the phenotypic expression of an entirely separate gene.