Mitosis and Meiosis Vocabulary Flashcards

Comprehensive vocabulary flashcards covering prokaryotic and eukaryotic chromosomes, cell cycle phases, mitosis, meiosis, gametogenesis, and sex determination mechanisms.

Prokaryotes

Single-celled organisms (bacteria and archaea) that lack a membrane-bound nucleus and typically possess a single circular chromosome located in the nucleoid region.

Eukaryotes

Organisms (protists, fungi, plants, and animals) whose cells contain a membrane-bound nucleus and other membrane-bound organelles such as mitochondria, endoplasmic reticulum, and Golgi body.

Nucleoid

The non-membrane-bound region within a prokaryotic cell where the circular chromosome is condensed by histone-like proteins.

Binary Fission

An asexual reproduction process in prokaryotes where a bacterial cell replicates its circular chromosome bidirectionally from the origin of replication and divides into two daughter cells.

Karyotype

An organized representation of the full set of chromosomes within a cell, visible during active cell division.

Nucleosome

The fundamental structural unit of eukaryotic chromatin, consisting of $2\,nm$ wide DNA wrapped around histone proteins.

Chromatin

The DNA-protein complex formed by nucleosomes that condenses further to form eukaryotic chromosomes during cell division.

Telomeres

The protective caps at the two ends of linear eukaryotic chromosomes, composed of specialized proteins and repetitive DNA sequences ($\text{TTAGGG}$).

Centromere

A region of repetitive satellite DNA on a eukaryotic chromosome that links a pair of sister chromatids and serves as the assembly site for kinetochore proteins.

Kinetochore

A protein complex assembled at the centromere of a chromosome that serves as the attachment point for mitotic or meiotic spindle fibers.

Homologs

Members of a pair of homologous chromosomes in a diploid organism that are nearly identical in size, banding pattern, and centromere location, carrying the same genes at identical loci.

$G_0$ Phase

A non-dividing state of the eukaryotic cell cycle occupied by cells that are temporarily not dividing or terminally differentiated cells such as neurons.

Interphase

The portion of the eukaryotic cell cycle between nuclear divisions, comprising the $G_1$, S, and $G_2$ phases.

$G_1$ Phase

The first gap phase of interphase in which the cell enters the cell cycle, synthesizes proteins and organelles, and prepares to divide.

S Phase

The synthesis phase of interphase during which DNA replication, histone synthesis, nucleosome replication, and chromosome duplication occur, converting $46$ single chromosomes into $92$ chromatids in human cells.

$G_2$ Phase

The second gap phase of interphase during which the cell accumulates materials for mitosis, synthesizes proteins such as microtubules, and repairs DNA replication damage.

$G_1$/S Checkpoint

A cell cycle restriction point that evaluates cell growth and DNA integrity before allowing the cell to enter S phase or return to $G_0$.

$G_2$/M Checkpoint

A cell cycle checkpoint that verifies whether all chromosomes are successfully duplicated and DNA damage is repaired prior to entering M phase.

Mitosis

The process of nuclear division in eukaryotic cells that distributes replicated chromosomes equally to the nuclei of two genetically identical daughter cells.

Prophase (Mitosis)

The initial phase of mitosis during which chromatids condense into compact structures, the nuclear envelope dissociates into small vesicles, and centrosomes begin to separate.

Prometaphase (Mitosis)

The stage of mitosis during which the nuclear envelope breakdown completes, spindle poles form at opposite ends, and kinetochore microtubules capture sister chromatids.

Metaphase (Mitosis)

The mitotic phase in which pairs of sister chromatids (dyads) align along the metaphase plate attached to opposite poles by kinetochore microtubules.

Anaphase (Mitosis)

The stage of mitosis in which sister chromatid connections break, kinetochore microtubules shorten to move individual chromosomes to opposite poles, and polar microtubules lengthen to push poles apart.

Telophase (Mitosis)

The final stage of mitosis in which chromosomes reach their respective poles, decondense back into chromatin, and nuclear membranes reform around two separate nuclei.

Astral Microtubules

Spindle microtubules that radiate outward from the centrosomes and are important for positioning the spindle apparatus within the cell.

Polar Microtubules

Spindle microtubules that project toward the cell center and overlap to push the two spindle poles away from each other.

Kinetochore Microtubules

Spindle microtubules that attach directly to kinetochore proteins bound to the centromere of each individual chromosome.

Mitotic Spindle

The apparatus composed of centrosomes and three types of microtubules (astral, polar, and kinetochore) that organizes and separates chromosomes during mitosis.

Cytokinesis

The division of the cytoplasm following nuclear division, producing two distinct daughter cells.

Cleavage Furrow

A constriction formed at the cell equator in animal cells during cytokinesis to divide the cell into two daughter cells.

Cell Plate

A membrane-bound partition formed at the middle of a dividing plant cell during cytokinesis that develops into a new cell wall.

Somatic Cells

Diploid ($2N$) body cells of an organism, excluding gametes, containing $46$ chromosomes in humans.

Germ Cells

Diploid precursor cells located in reproductive organs that undergo meiotic division to produce haploid ($1N$) gametes.

Meiosis

A specialized cell division process involving two successive divisions (Meiosis I and II) that reduces the chromosome number of diploid germ cells by half to produce four haploid gametes.

Synapsis

The process during prophase of meiosis I in which homologous chromosomes pair closely together to form a bivalent or tetrad.

Bivalent

A structure formed during synapsis in prophase I consisting of two paired homologous chromosomes (a tetrad containing four chromatids or monads).

Crossing Over

The physical exchange of DNA segments between homologous chromosomes at chiasmata loci during prophase of meiosis I.

Chiasmata

The X-shaped connection points where non-sister chromatids of homologous chromosomes cross over and exchange genetic material during prophase I of meiosis.

Independent Assortment

The random arrangement and distribution of maternal and paternal homologous chromosomes along the metaphase plate during metaphase I, promoting genetic diversity.

Isogamous

Describing species (such as many fungi and algae) that produce morphologically identical gametes.

Heterogamous

Describing species that produce morphologically distinct male (small, mobile sperm) and female (large, nonmotile egg) gametes.

Oogenesis

The process of female gamete formation in the ovaries, resulting in one large functional haploid egg cell and small polar bodies.

Primary Oocyte

A diploid female germ cell formed before birth that initiates meiosis I and remains arrested in prophase I until sexual maturity.

Secondary Oocyte

A large haploid cell produced along with a small first polar body via asymmetric division during meiosis I of oogenesis.

Polar Body

A small haploid cell containing minimal cytoplasm generated as a byproduct of asymmetric meiotic divisions during oogenesis.

Spermatogenesis

The continuous process of male gamete production in the testes, where a diploid primary spermatocyte undergoes symmetric meiotic divisions to produce four haploid sperm cells.

SRY Gene

A gene on the mammalian Y chromosome that encodes Sex-determining region Y protein (also known as testis-determining factor or TDF) to direct male development.

Protandrous Hermaphrodites

Organisms (such as clownfish) that mature initially as males and can change sex to become females in response to environmental or behavioral triggers.