Human Biology Chapter 19: Cell Division

Comprehensive vocabulary flashcards covering human chromosomes, the cell cycle, mitosis, meiosis, and chromosomal inheritance based on Chapter 19 of Human Biology, 17th Edition.

Chromosomes

Structures made of DNA and proteins that contain genes, which are the instructions for directing all functions in the body.

Chromatin

The collective term for DNA and the proteins that assist in its organizational structure within the nucleus.

Autosomes

The 22 pairs of chromosomes found in both males and females that do not control gender.

Sex Chromosomes

The pair of chromosomes (X and Y) that contain genes controlling the gender of an individual.

SRY Gene

A gene located on the Y chromosome that causes testes to develop in males.

Karyotype

A display of the chromosomes present in a cell, paired up by a computer based on size, shape, and banding patterns produced by staining.

Mitosis

A type of nuclear division, also called duplication division, that ensures every new cell is diploid ($2n = 46$ chromosomes).

Sister Chromatids

Two identical parts of a duplicated chromosome that contain the same genes and are held together at a centromere.

Genes

The units of heredity that control traits, such as eye color and metabolism.

Centromere

The region that holds sister chromatids together until cell division separates them into daughter chromosomes.

Cell Cycle

An orderly set of stages that includes interphase and cell division (mitosis and cytokinesis).

Interphase

The portion of the cell cycle where the cell performs usual functions, grows, and replicates its DNA; consists of $G_1$, $S$, and $G_2$ stages.

$G_1$ Stage

The stage of interphase where the cell performs normal functions, doubles its organelles, and accumulates materials for DNA synthesis.

$S$ Stage

The stage of interphase characterized by DNA replication, resulting in chromosomes consisting of two identical sister chromatids.

$G_2$ Stage

The stage of interphase following DNA replication where the cell synthesizes proteins needed for division.

$G_0$ Stage

A state of permanent arrest in the cell cycle for cells that do not continue to the $S$ and $G_2$ phases, such as nerve and muscle cells.

Cytokinesis

The division of the cytoplasm and organelles following nuclear division.

Apoptosis

Programmed cell death that occurs when cells are no longer needed or are excessively damaged.

Checkpoints

Regulatory points ($G_1$, $G_2$, and Mitotic) in the cell cycle that delay progression until certain conditions are met.

p53

A protein that can stop the cell cycle at the $G_1$ checkpoint if DNA is damaged, potentially triggering apoptosis.

Signal Transduction Pathway

A series of proteins that pass an external signal (like a hormone or growth factor) from a receptor to the nucleus to stimulate or inhibit the cell cycle.

Proto-oncogenes

Genes that produce proteins to stimulate the cell cycle.

Tumor Suppressor Genes

Genes that produce proteins to inhibit the cell cycle.

Centrosome

The microtubule organizing center of the cell that duplicates to form the poles of the mitotic spindle.

Aster

An array of microtubules extending from the centrosomes at the poles of the spindle.

Prophase

The first phase of mitosis where centrosomes move to opposite ends, spindle fibers appear, the nuclear envelope fragments, and chromosomes condense.

Metaphase Plate

A plane perpendicular to the axis of the spindle and equidistant from the poles where chromosomes line up during metaphase.

Anaphase

The phase of mitosis where centromeres divide and sister chromatids separate to move toward opposite poles.

Cleavage Furrow

An indentation in the cell membrane that pins the cell in half during cytokinesis, formed by a contractile ring of actin filaments.

Meiosis

Reduction division resulting in four haploid ($n$) daughter cells that are genetically different from the parent cell.

Homologous Chromosomes

Pairs of chromosomes (homologues) that look alike and carry genes for the same traits.

Synapsis

The process during Meiosis I where homologous chromosomes come together and line up side by side.

Interkinesis

The period of time between Meiosis I and Meiosis II, during which DNA does not replicate.

Crossing-over

The exchange of genetic material between non-sister chromatids of a homologous pair during Prophase I.

Spermatogenesis

The process of sperm production in the testes of males, resulting in four functional sperm from one primary spermatocyte.

Oogenesis

The process of egg production in the ovaries of females, resulting in one functional egg and two or three non-functional polar bodies.

Secondary Oocyte

The haploid cell in oogenesis that receives almost all the cytoplasm and arrests at Metaphase II until fertilization.

Polar Body

A small haploid cell produced during oogenesis that serves as a way to discard unnecessary chromosomes while conserving cytoplasm for the egg.

Genetic Recombination

The process, resulting from crossing-over and independent alignment, that ensures offspring are genetically different from their parents and each other.

Alleles

Slightly different variations of genes for particular traits.

Nondisjunction

The failure of homologous chromosomes or daughter chromosomes to separate correctly during meiosis I or II.

Trisomy

A chromosomal condition where one type of chromosome is present in three copies ($2n + 1$).

Monosomy

A chromosomal condition where one type of chromosome is present in only a single copy ($2n - 1$).

Barr Body

An inactive X chromosome found in the cells of normal females.

Down Syndrome

The most common autosomal trisomy, characterized by three copies of chromosome 21.

Turner Syndrome

A condition in females (XO) characterized by having only one X chromosome, resulting in short stature and underdeveloped reproductive organs.

Klinefelter Syndrome

A condition in males ($47, XXY$) who have two X chromosomes and one Y chromosome, often resulting in underdeveloped testes and long limbs.

Jacobs Syndrome

A condition in males (XYY) resulting from nondisjunction during spermatogenesis, often characterized by tall stature and persistent acne.

Deletion

A change in chromosome structure where a part of a chromosome breaks off.

Duplication

The presence of a chromosomal segment more than once in the same chromosome.

Inversion

A chromosomal mutation where a segment of a chromosome is turned around 180 degrees.

Translocation

The movement of a chromosome segment from one chromosome to another nonhomologous chromosome.

Williams Syndrome

A deletion syndrome where chromosome 7 loses an end piece, affecting the cardiovascular system and causing premature skin aging.

Cri du chat Syndrome

A deletion syndrome where chromosome 5 is missing an end piece, resulting in a cry that resembles that of a cat.

Alagille Syndrome

A translocation syndrome between chromosomes 2 and 20, characterized by heart defects known as tetralogy of Fallot.