Cell Cycles, Chromosomes, Mitosis, and Meiosis

Flashcards on Cell Biology and Genetics

Cell Cycle

A rhythmic recurrence of growth within the cell followed by reproduction of the cell.

Mitosis

The distribution of nuclear materials, particularly the chromosomes, during cell division.

Cytokinesis

The apportionment of cytoplasm during cell division.

G1 Phase

The phase of the cell cycle where vegetative (nonreproductive) functions occur, including growth and organelle production.

S Period

The phase of the cell cycle when DNA in the nucleus doubles.

G2 Phase

The phase of the cell cycle during which materials for chromosome movement and cell replication are organized.

Gametes

Special sex cells that unite to incorporate genetic material from two different sources during sexual reproduction.

Zygote

The fusion product of two gametes.

Diploid State (2n)

The condition of having two sets of chromosomes.

Haploid State (1n)

The condition of having only a single set of chromosomes.

Meiosis

A process of chromosome reduction that produces up to four haploid cells from a diploid cell.

Sporophyte

The diploid phase in the life cycle of a fern, consisting of roots, stems, and leaves.

Gametophyte

The haploid phase in the life cycle of a fern, a small heart-shaped structure that produces sperm and egg.

Alternation of Generations

The swing from a haploid gametophyte to a diploid sporophyte in the life cycle of some plants.

DNA

The fundamental blueprint molecule containing information for carrying out the activities of every cell.

Histones

Small basic proteins associated with DNA in eukaryotic chromosomes.

Nucleosome

A unit formed by a set of eight histone molecules around which DNA is wound.

Chromatin Fibers

Dense bands formed by further coiling of DNA and nucleosomes.

Karyotype

The particular number and characteristic morphology for a species' chromosome sets.

Trisomy

The situation where a third chromosome is found in cells, such as in Down's syndrome (an extra chromosome 21).

Centromere

A constricted region of a chromosome where chromatids are joined.

Kinetochores

Protein rings within the centromere that attach to spindle fibers during cell division.

Centrosome

A region outside the nuclear membrane in animal cells and some fungi, containing centrioles.

Centrioles

Cylindrical rodlets that occur in pairs within the centrosome and appear to be associated with the spindle apparatus.

Spindle Apparatus

A rigid, semisolid network of microtubules responsible for the migratory movements of chromosomes during mitosis and meiosis.

Telophase

The last phase of mitosis, where chromosomes lose stainability, the nucleolus re-forms, and a new nuclear membrane forms.

Cytokinesis

The division of the cytoplasm that occurs after nuclear division (mitosis or meiosis).

Phragmoplast

A ringed structure made of protein observed during cytokinesis in plant cells before the formation of the cell plate.

Oogonia

Diploid cells in the ovary that produce eggs (ova).

Spermatogonia

Diploid cells within the testes that proliferate mitotically and undergo modification to become primary spermatocytes.

Synapsis

The coming together of homologous chromosomes in pairs during prophase I of meiosis.

Tetrad

The intimate four-stranded structure formed when homologous chromosomes zip together during synapsis.

Chiasmata

Physical links between chromatids of homologous chromosomes where sections have broken off and exchanged.

Crossing Over

The exchange of chromosome parts between the chromatids of two homologous chromosomes.

Recombination Nodules

Proteinaceous thickening within the crossbands of the synaptinemal complex that are thought to play a part in snipping homologous chromatids.

Synaptinemal Complex

A complex structure in chromosomes undergoing synapsis, consisting of longitudinal protein rods and lateral processes that connect all four chromatids.

Disjunction

The separation of chromosomes during meiosis.