Essentials of Genetics - Mitosis and Meiosis

Flashcards on Mitosis and Meiosis

Mitosis

Cell division that leads to two cells, each with the same number of chromosomes as the parent cell (2n).

Meiosis

Reduces genetic content and leads to the production of sex gametes, which contain half the number of chromosomes (n).

Chromatin

Uncoiled chromosomes that form a diffuse network within the nucleus.

Prokaryotic Cell

A nonnucleated cell; example: bacteria and archaea.

Eukaryotic Cell

A nucleated cell; example: protists, plants, fungi, and animals.

Nucleolus

The location where rRNA is synthesized and initially assembled in eukaryotic cells.

NOR (Nucleolus Organizer Region)

Portions of DNA that encode rRNA.

Nucleoid Area

A compacted area of genetic material (long, circular DNA molecule) in prokaryotic cells.

Locus

The location of an identical gene site along the length of homologous chromosomes.

Allele

Alternative forms of the same gene.

Zygote

A single-celled fertilized egg.

Karyokinesis

The process where genetic material is evenly divided into two daughter cells during nuclear division.

Cytokinesis

Follows karyokinesis; cytoplasmic division that partitions cellular volume into two parts and encloses each cell with a plasma membrane.

Cohesin

A protein complex that holds sister chromatids together.

Kinetochore

Protein layers where spindle fibers bind to during prometaphase/metaphase and move chromosomes.

Separase

The enzyme that degrades cohesin, allowing sister chromatids arms to disjoin.

Shugoshin

An enzyme that prevents degradation of cohesin at the centromere.

Kinases

Enzyme products of mutated genes that serve as 'master control' molecules.

Cyclins

Proteins that bind with kinases, activating them at appropriate times during the cell cycle.

Bivalent

Each synapsed pair of homologs during meiosis I.

Tetrad

A unit of two pairs of sister chromatids that arises from each bivalent during synapsis in meiosis.

Chiasma

A region where chromatids are still intertwined; The point where nonsister chromatids have undergone genetic exchange through crossing over.

Dyad

Half of each tetrad; separated homologous chromosomes that are pulled to opposite poles during anaphase I.

Monad

One member of each homologous chromosome at each pole during telophase II.

Spermatogenesis

The process that begins when an undifferentiated spermatogonium germ cell enlarges to become a primary spermatocyte.

Spermiogenesis

The developmental changes that spermatids undergo to become motile spermatozoa or sperm.

Oogenesis

The formation of ova in the ovaries.

Ootid

One of the two haploid cells produced when the secondary oocyte divides unequally.

Folded-fiber model

Model based on electron microscopic observations of metaphase chromosomes