Chapter 8: Cell Division, Reproduction, and Genetics

Vocabulary terms and definitions covering the mechanisms of cell division, mitosis, meiosis, regulation, and chromosomal alterations.

Binary fission

A type of asexual reproduction in prokaryotic cells that literally means "dividing in half."

Asexual reproduction

The creation of offspring by a single parent, producing offspring that are all genetic copies of the parent and identical to each other (clones).

Chromatin

Thin, loosely packed fibers of DNA and associated proteins that are too small to be seen under a light microscope when a eukaryotic cell is not dividing.

Sister chromatids

Duplicated copies of a chromosome that contain identical DNA and are joined together along their lengths before cell division.

Cell cycle

An ordered sequence of events that extends from the time a cell is first formed from a dividing parent cell until its own division into two cells.

Mitosis

The division of a single nucleus into two genetically identical daughter nuclei, distributing duplicated chromosomes to opposite poles of the cell.

Mitotic spindle

A structure made of microtubules that moves chromosomes to the middle of the cell during cell division.

Cytokinesis

The division of the cytoplasm to form two separate daughter cells, which overlaps the end of mitosis.

Cleavage furrow

A shallow groove or constriction in an animal cell that pinches the parent cell into two daughter cells during cytokinesis.

Cell plate

A membranous structure that forms across a dividing plant cell during cytokinesis and eventually splits the cell into two.

Growth factors

Proteins that bind to specific receptors on the plasma membrane to stimulate cells to divide.

Cell cycle control system

A set of proteins within the cell that triggers and coordinates key events and regulates progression through critical checkpoints in the cell cycle.

Malignant tumors

Abnormally dividing masses of cancer cells that can invade other tissues, disrupt organ function, and spread throughout the body.

Somatic cells

Any cell in a multicellular organism except a sperm or egg cell, containing a specific number of chromosomes (such as $46$ in humans).

Homologous chromosomes

A matched pair of chromosomes carrying genes controlling the same characteristics at corresponding loci.

Locus

The particular place or location on a chromosome where a gene is found.

Diploid

Containing two complete sets of homologous chromosomes, one inherited from each parent.

Gametes

Haploid sex cells—eggs and sperm—that contain a single set of chromosomes.

Meiosis

A form of cell division in sexually reproducing organisms involving two rounds of division to produce four genetically unique haploid daughter cells.

Crossing over

The reciprocal exchange of corresponding segments between nonsister chromatids of homologous chromosomes during prophase I of meiosis.

Genetic recombination

The production of offspring with gene combinations different from those in the parents, resulting from crossing over during prophase I.

Nondisjunction

An accident during meiosis where a pair of homologous chromosomes fails to separate in meiosis I or sister chromatids fail to separate in meiosis II.

Karyotype

A photographic inventory of an individual's chromosomes, prepared by arresting white blood cells at metaphase and ordering them into pairs.

Trisomy 21

The most common chromosomal number abnormality resulting from an extra copy of chromosome $21$, causing Down syndrome.

Polyploid organisms

Organisms that have extra complete sets of chromosomes due to errors in cell division such as nondisjunction.