Key Terms and Definitions for Biology

Anaphase

third sage of mitosis, chromatids are separated and pulled to the centrosomes

Asexual reproduction

creation of genetically identical offspring by a single parent

autosome

a chromosome not directly involved in determining the sex of an organism

benign tumor

an abnormal mass of cells that remains art its original site in the body

cancer

a malignant growth or tumor caused by abnormal and uncontrolled cell division

cell cycle

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

cell cycle control system

a cyclically operating set of proteins that triggers and coordinates events in the eukaryotic cell cycle

cell division

the reproduction of a cell

cell plate

a membranous disk that forms across the midline of a dividing plant cell

centromere

the region of a chromosome where two sister chromatids are joined and where spindle microtubules attach during meiosis and mitosis

centrosome

material in the cytoplasm of a eukaryotic cell that gives rise to microtubules

chemotherapy

treatment for cancer in which drugs are administered to disrupt cell division of the cancer cells

chiasma

the microscopically visible site where crossing over has occurred between chromatids of homologous chromosomes during prophase I of meiosis

chromatin

the combination of DNA and proteins that constitutes chromosomes

chromosome

a gene-carrying structure found in the nucleus of a eukaryotic cell and is most visible during meiosis and mitosis

cleavage furrow

the first sign of cytokinesis during cell division in an animal cell

crossing over

when the chromosome cross over each other

cytokinesis

the division of the cytoplasm to form two separate daughter cells

diploid

containing two sets of chromosomes in each cell, referring to a 2n cell

down syndrome

a human genetic disorder resulting from a condition called trisomy 21

fertilization

the union of a haploid sperm cell with a haploid egg, producing a zygote

gamete

a sex cell

genetic recombination

the production of offspring with gene combinations that differ from that found in either parent

haploid

containing a single set of chromosomes, referring to an n cell

histone

a small protein molecule associated with DNA and important in DNA packing in the eukaryotic chromosome

homologous chromosome

the two chromosomes that make up a matched pair in a diploid cell

interphase

normal cell functioning and preparation for division,
the phase contains, G1, S, and G2

karyotype

a display of micrographs of the metaphase chromosomes of a cell, arranged by size and centromere position

life cycle

the entire sequence of stages in the life of an organism

malignant tumor

an abnormal tissue mass that spreads into neighboring tissue and to other parts of the body, a cancerous tumor

meiosis

in a sexually reproducing organism, the process of cell division that produces haploid gametes from diploid cells within reproductive organs

metaphase

second stage of mitosis, chromosomes are pulled to the middle

metastasis

the spread of cancer cells beyond their original cancer site

mitosis

the division of a single nucleus into tow genetically identical daughter nuclei

mitotic (M) phase

the phase of the cell cycle when mitosis divides the nucleus and distributes its chromosomes to the daughter nuclei and cytokinesis divides the cytoplasm, producing two daughter cells

mitotic spindle

a spindle-shaped structure formed of microtubules and associated proteins that is involved in the movement of chromosomes during mitosis and meiosis

nucleosome

the bead-like unit of DNA packing in a eukaryotic cell

nondisjunction

an accident of meiosis or mitosis in which a pair of homologous chromosomes or a pair of sister chromatids fail to separate at anaphase

prophase

first phase of mitosis, where the nuclear embryo dissolves, chromosomes condense, centrosomes migrate, and the spindle forms

radiation therapy

treatment for cancer in which parts parts of the body that have cancerous tumors are exposed to high-energy to disrupt cell division of the cancer cells

sex chromosome

a chromosome that determines whether an individual is male or female

sexual reproduction

the operation of genetically distinct offspring by the fusion of two haploid sex cells

sister chromatid

one of the two identical parts of a duplicated chromosome

somatic cell

a body cell

telophase

fourth stage or mitosis, reverse prophase and formation of two new nuclei

trisomy 21

the presence of an extra chromosome

tumor

an abnormal mass of cells that forms within otherwise normal tissue

zygote

the fertilized egg