Cell Division

Asexual Reproduction

Reproduction involving one parent that produces genetically identical offspring

Sexual Reproduction

Reproduction involving two parents whose genetic material combines to produce unique offspring

Binary Fission

The method of prokaryotic reproduction where the cell replicates its DNA and splits into two identical cells

Chromatin

The loose uncoiled form of DNA wrapped around proteins found in the nucleus when a cell is not dividing

Chromosome

The condensed coiled form of DNA visible during cell division; humans have 46

Sister Chromatids

Two identical copies of a chromosome joined at the centromere after DNA replication

Centromere

The pinched region that holds sister chromatids together and serves as the attachment point for spindle fibers

Interphase

The longest phase of the cell cycle consisting of G1 S and G2 where the cell grows and replicates DNA

Cell Cycle

The ordered sequence of events from a cell's creation to its division into two daughter cells

Mitotic Phase

The portion of the cell cycle when the cell actually divides including mitosis and cytokinesis

Mitosis

The process of nuclear division producing two genetically identical daughter nuclei; stages are prophase metaphase anaphase telophase

Cytokinesis

The division of the cytoplasm following mitosis to produce two separate daughter cells

Mitotic Spindle

A structure made of protein fibers that attaches to chromosomes and pulls them apart during cell division

Kinetochore

A protein structure on the centromere where spindle fibers attach during mitosis and meiosis

Motor Proteins

Proteins that move along microtubules and power chromosome movement during cell division

Centrosome / Centrioles

The microtubule-organizing center in animal cells that organizes spindle fibers during division

Prophase

First stage of mitosis; chromosomes condense and the spindle begins to form

Prometaphase

Stage of mitosis when the nuclear envelope breaks down and spindle fibers attach to kinetochores

Metaphase

Stage of mitosis when chromosomes align along the middle of the cell at the metaphase plate

Metaphase Plate

The imaginary line at the center of a dividing cell where chromosomes align during metaphase

Anaphase

Stage of mitosis when sister chromatids are pulled apart to opposite poles of the cell

Telophase

Final stage of mitosis; nuclear envelopes reform around chromosomes at each pole

Cell Plate

A structure that forms in plant cells during cytokinesis and develops into a new cell wall

Cleavage Furrow

The indentation that forms in animal cells during cytokinesis where the cell pinches in two

G1 S G2

The three sub-phases of interphase

DNA Replication

The process of copying all of a cell's DNA before cell division; occurs during the S phase of interphase

Anchorage Dependence

The requirement that normal cells must be attached to a surface before they will divide

Density-Dependent Inhibition

The property of normal cells to stop dividing when they become too crowded

Cell Cycle Control System

The system of proteins (cyclins and kinases) that regulate checkpoints in the cell cycle

Tumor (Benign vs Malignant)

An abnormal mass of dividing cells; benign stays in one place while malignant spreads and is cancerous

Metastasis

The spread of cancerous cells from the original tumor to other parts of the body

Meiosis I and II

Cell division producing four haploid gametes; Meiosis I separates homologs and Meiosis II separates chromatids

Karyotype

A photograph of chromosomes arranged in matching pairs used to detect chromosomal abnormalities

Homologous Chromosomes

Pairs of chromosomes carrying the same genes in the same locations; one from each parent

Sex Chromosomes (X Y)

The pair of chromosomes that determines biological sex; females are XX and males are XY

Autosomes

The 22 pairs of non-sex chromosomes in humans

Gametes (Sex Cells)

Haploid reproductive cells (sperm and egg) produced by meiosis

Somatic (Body) Cells

All body cells except gametes; diploid cells that divide by mitosis

Fertilization

The fusion of sperm and egg to form a diploid zygote

Zygote

The diploid cell formed when a sperm fertilizes an egg; the first cell of a new organism

Diploid (2n)

Having two complete sets of chromosomes; in humans this equals 46 chromosomes

Haploid (n)

Having one set of chromosomes; in humans this equals 23 chromosomes; found in gametes

Gene Locus

The specific fixed location of a gene on a chromosome

Tetrad

The structure of four chromatids formed when homologous chromosomes pair up during Meiosis I

Crossing Over

The exchange of DNA segments between homologous chromosomes during Meiosis I creating new allele combinations

Chiasma (Chiasmata)

The X-shaped point where two homologous chromosomes are physically joined during crossing over

Genetic Recombination

The reshuffling of genes due to crossing over and independent assortment during meiosis

Synapsis

The pairing of homologous chromosomes during prophase I of meiosis

Nondisjunction

An error where chromosomes fail to separate properly during meiosis resulting in gametes with too many or too few chromosomes

Monosomy / Trisomy

Conditions from nondisjunction; monosomy is missing one chromosome (2n-1) and trisomy is an extra chromosome (2n+1)