D.2.1 Cell and nuclear division

Based on the 3rd edition biology textbook written by C.J. Clegg, Andrew Davis, Christopher Talbot

parent cell

cell that divides to form daughter cells by mitosis or meiosis

daughter cells

cells produced when a cell divides by mitosis or meiosis

cytokinesis

splitting of cytoplasm in a parent cell between daughter cells, following the division of the nucleus

mitosis

nuclear division in which the daughter nuclei have the same number of chromosomes as the parent cells

meiosis

nuclear division with daughter cells (gametes) containing half the number of chromosomes of the parent cell

diploid

cells with nuclei containing two sets of chromosomes

haploid

cells with nuclei containing one set of chromosomes

interphase

the period between nuclear divisions when the nucleus controls and directs the activity of the cell and replicates chromosomes

chromatid

one of two copies of a chromosome after it has replicated, joined, together at a centromere

centromere

constriction of the chromosome, the region that becomes attached to the spindle fibres during nuclear division

histone

protein (rich in the amino acids arginine and lysine) that forms the scaffolding of chromosomes and is used in chromosome condensation to form nucleosomes

nucleosome

the basic unit of eukaryotic chromosome structure consisting of a ball of eight histone molecules wrapped about by two coils of about 220 base pairs of DNA

supercoiled

form of DNA in which the double helix is further twisted about itself within nucleosomes, forming a tightly coiled structure

prophase

first stage in nuclear division or meiotic, where the chromosomes condense and centrioles move to the poles of the cell

metaphase

stage in mitosis in which chromosomes become arranged at the equator of the spindle

anaphase

stage in nuclear division where chromosomes move away from one another to opposite poles of the cell

telophase

a phase in the nuclear division when the nuclear membrane reforms around daughter cell nuclear material

proliferation

increase in the number of cells as a result of cell growth and cell division

meristem

a group of cells in plants that retains the ability to divide by mitosis and form new cells and tissues throughout the life of a plant

cell proliferation

the process of generating an increased number of cells through cell division (mitosis)

cell cycle

repeating process of an orderly sequence of events where cells arise by the division of existing cells, grow, and then divide

cyclin

regulatory protein whose concentration rises and fells at specific times during the eukaryotic cell cycle

kinases

enzymes that either activate or inactivate other proteins, their “turn on“ are cyclins.

proto-oncogene

gene that codes for proteins that stimulate the cell cycle and promote cell growth and proliferation

oncogene

a gene that when activated cab potentially make a cell cancerous. Typically a mutant form of a normal gene (proto-oncogene) involved in the control of cell growth or division

tumour-suppressor gene

a gene that in a normal tissue cell inhibits cancerous behaviour. Loss or inactivation of both copies of such a gene from a diploid cell can cause it to behave as a cancer cell

benign tumour

a tumour that tends to grow slowly and does not spread to other parts of the body

malignant tumour

a tumour that grows rapidly, invades and destroys nearby normal tissues and spreads throughout the body

primary tumour

a cancer growing at the site where the abnormal growth first occured

secondary tumour

formed when cancerous cells detach from the primary tumour, penetrate the walls of lymph or blood vessels and circulate around the body causing tumours elsewhere

metastasis

the movement of cells from a primary tumour to set up secondary tumours

mitotic index

the number of cells undergoing mitosis is divided by the total number of cells visible which can also be shown as a percentage

bivalent

a pair of duplicated homologous chromosomes, held together by chiasmata during meiosis

chiasma

sire of crossing over (exchange) of segments of DNA between homologous chromosomes during meiosis

crossing over

exchange of genetic material between two homologous chromosomes during meiosis

non-disjunction

the failure of homologous chromosomes or sister chromatids to separate properly during meiosis

down-syndrome

a congenital condition in which a person has an extra 21st chromosome as a result of non-disjunction

random orientation

refers to the way chromosomes line up in the centre (equator) of the cell during meiosis, with each chromosome of a given pair behaving independently to the chromosomes in other pairs; it results in each sperm and each egg having different combinations of chromosomes from the mother and father

metaphase 1

stage in meiosis in which chromosomes become arranged at the equator of the spindle forming tetrads; this is when crossing over happens

prophase 2

stage in meiotic, where the chromosomes condense, and centrioles move to the poles of the cell; this time, centrioles are formed at a right-degree angle from meiosis 1