Cell Cycle Regulation and Mendelian Genetics

Vocabulary practice flashcards covering cell cycle regulation, molecular checkpoints, apoptosis, and foundational principles of Mendelian genetics.

Mitosis

The cell division process whose overall goal is to produce two daughter cells that are genetically identical to the parent cell.

Meiosis

A specialized cell division occurring exclusively in cells that give rise to gametes, resulting in daughter cells that are genetically diverse from each other and the parental cell due to crossing over and independent assortment.

$G_0$ Phase ($G$ naught)

A non-dividing state exited from $G_1$ wherein terminally differentiated cells permanently cease division for the remainder of their lifetime.

Restriction Checkpoint (R Checkpoint)

The $G_1$ to $S$ checkpoint where a cell determines whether to commit to replicating its DNA and dividing; failure past this commitment point typically induces programmed cell death.

$S$ Checkpoint

A regulatory mechanism ensuring that DNA replication has been completed, is as error-free as possible, and that major damaged DNA is repaired before exiting the synthesis phase.

$G_2$ Checkpoint

A gap-phase checkpoint where the cell confirms the presence of adequate space, nutrients, and external pro-division signals, while providing an additional opportunity to repair DNA damage.

Mitotic Checkpoint (M Checkpoint)

A checkpoint that ensures all chromosomes are properly aligned on the metaphase plate and that a spindle microtubule is attached to each sister chromatid prior to separation.

Cyclin-Dependent Kinase (CDK)

A protein kinase present at constant, steady-state levels throughout the cell cycle that remains enzymatically inactive until bound non-covalently to its specific cyclin partner.

Cyclin

A regulatory protein whose concentration fluctuates cyclically through regulated transcription, translation, and rapid degradation to activate its corresponding cyclin-dependent kinase.

Retinoblastoma Protein (Rb)

A master regulator protein that functions as an inhibitory brake preventing exit from $G_1$; it must be inactivated by phosphorylation by the $G_1/S$ cyclin-CDK complex to allow entry into $S$ phase.

p16

A regulatory protein that inhibits cell cycle progression by blocking the cyclin-CDK-mediated phosphorylation and inactivation of the Rb protein.

Apoptosis

Programmed cell death characterized by the orderly autodigestion of organelles and packaging of cellular contents into small blebs for phagocytic clearance without triggering an inflammatory response.

Perfect Flower

A flower structure containing both male reproductive organs (stamens) and female reproductive organs (pistils), permitting self-fertilization.

Stamen

The pollen-producing male reproductive organ of a flower, terminating in pollen-bearing structures called anthers.

Pistil

The female reproductive structure of a flower consisting of a sticky landing surface (stigma) that receives pollen and connects to the ovule.

True Breeding

Strains or lines that produce offspring with identical phenotypic traits $100\%$ of the time upon self-fertilization due to carrying two identical copies of an allele (homozygous).

Phenotype

The observable physical manifestation or measurable characteristic of a trait displayed by an organism.

Genotype

The actual nucleotide sequences or specific combination of alleles present in an organism's DNA.

Dominant Allele

An allele whose corresponding phenotype is fully expressed in the $F_1$ generation of a monohybrid cross, masking the expression of an alternate recessive allele.

Recessive Allele

An allele whose phenotypic effect is masked in the $F_1$ hybrid generation and only reappears in the $F_2$ generation when homozygous.

Gene

A distinct DNA sequence located at a specific chromosomal locus that encodes a particular functional protein product.

Allele

Alternative sequence variations or versions of a specific gene found at the same chromosomal locus.

SBE1 Gene

The gene encoding a starch-synthesizing enzyme; the wild-type dominant allele produces round, plump seeds filled with starch and water, while an $800$-base-pair insertion mutation produces wrinkled seeds.

Wild Type Allele

The specific allele version of a gene found most frequently in natural populations, which does not inherently equate to being a dominant allele.

Homozygous

A genetic condition in which an individual carries two identical alleles for a specific gene locus.

Heterozygous

A genetic condition in which an individual possesses two different alleles for a specific gene locus.

Hemizygous

A genetic state occurring in $XY$ individuals where only a single copy of an $X$-linked gene is present, causing any allele on that $X$ chromosome to be expressed regardless of dominance.

Law of Segregation

Mendel's first law stating that during gamete formation (meiosis), the two alleles of a gene segregate equally such that $50\%$ of the resulting gametes carry one allele and $50\%$ carry the other.

Dihybrid Cross

A mating experiment tracking two distinct characters simultaneously between true-breeding parents, yielding a characteristic $9:3:3:1$ phenotypic ratio in the $F_2$ generation.

Law of Independent Assortment

Mendel's second law stating that the segregation of alleles for one gene occurs independently of the segregation of alleles for another gene located on different homologous chromosome pairs.