Terminology - SU 1

Prokaryote

A unicellular organism with a relatively simple cell structure including bac

Eukaryote

An organism that has a compartmentalized cell structure, including a nuclear envelope and membrane-bounded organelles. Eukaryotes may be unicellular or multicellular.

Nucleus

Compartment in eukaryotic cells that is enclosed by the nuclear membrane and contains the genetic material.

Histones

Low-molecular-weight protein found in eukaryotes that associates closely with DNA to form chromosomes.

chromatin

Homologous pair

A pair of chromosomes that are alike in structure and size and that carry genetic information for the same set of hereditary characteristics. One chromosome of a homologous pair is inherited from the male parent, and the other is inherited from the female parent.

Diploid

Possessing two sets of chromosomes (two genomes).

Haploid

Possessing a single sets of chromosomes (one genomes).

Polyploid

Possession of more than two sets of chromosomes.

Centromere

Constricted region on a chromosome that stains less strongly than the rest of the chromosome; serves as the attachment point for spindle microtubules.

Telomeres

Stable end of a eukaryotic chromosome.

Origins on replication

Site where DNA replication is initiated.

Sister chromatids

Two copies of a chromosome that are held together at the centromere. Each sister chromatid consists of a single molecule of DNA.

Cell cycle

Stages through which a cell passes from one cell division to the next.

Checkpoints

Major phase of the cell cycle between cell divisions. In interphase, the cell grows, develops, and functions.

Interphase

Major phase of the cell cycle between cell divisions. In interphase, the cell grows, develops, and functions.

M (mitotic) phase

The major phase of the cell cycle that encompasses active cell division; includes mitosis (nuclear division) and cytokinesis (cytoplasmic division).

Mitosis

Process by which the nucleus of a eukaryotic cell divides.

Cytokinesis

Process by which the cytoplasm of a cell divides.

Prophase

Stage of mitosis in which the chromosomes contract and become visible, the cytoskeleton breaks down, and the mitotic spindle begins to form.

Condensins

A group of proteins that bind to chromosomes as a cell enters prophase, causing the chromosomes to become more compact and visible under a light microscope.

Prometaphase

Stage of mitosis in which the nuclear membrane breaks down and the spindle microtubules attach to the chromosomes.

Metaphase

Stage of mitosis in which chromosomes align in the center of the cell.

Anaphase

Stage of mitosis in which sister chromatids separate and move toward opposite spindle poles.

Telophase

Stage of mitosis in which sister chromatids separate and move toward opposite spindle poles.

Meiosis

Process by which the chromosomes of a eukaryotic cell divide to give rise to haploid reproductive cells. Consists of two divisions: meiosis I and meiosis II.

Fertilisation

Fusion of gametes (sex cells) to form a zygote.

Crossing over

Exchange of genetic material between homologous but nonsister chromatids.

Metaphase I

Stage of meiosis I in which homologous pairs of chromosomes align in the center of the cell along the metaphase plate.

Anaphase I

Stage of meiosis I in which homologous chromosomes separate and move toward the spindle poles.

Telophase I

Interkinesis

Prophase II

Meta

Anaphase II

Telophase II

Recombination

Process that produces new combinations of alleles.

Cohesin

A protein that holds the two sister chromatids of a chromosome together. The breakdown of cohesin at the centromeres enables the chromatids to separate in anaphase of mitosis and anaphase II of meiosis.

Spermatogenesis

Production of gametes in a male animal; takes place in the testes.

Spermatogonia

Diploid cell in the testis; capable of undergoing meiosis to produce a sperm.

Primary Spermatocytes

Spermatogonium that has entered prophase I.

Secondary Spermatocytes

Product of meiosis I in male animals

Spermatids

Immediate product of meiosis II in spermatogenesis; matures to sperm.

Oogenesis

The production of gametes in a female animal.

Oogonia

Diploid cell in the ovary; capable of undergoing meiosis to produce an egg cell.

Primary oocyte

Oogonium that has entered prophase I.

Secondary Oocyte

One of the products of meiosis I in oogenesis; receives most of the cytoplasm.

First polar body

One of the products of meiosis I in oogenesis; the smaller cell, which contains half the chromosomes but only a small part of the cytoplasm.

Ovum

The mature female gamete; the larger cell, which acquires most of the cytoplasm during oogenesis.

Second polar body

One of the products of meiosis II in oogenesis; contains a set of chromosomes but little of the cytoplasm.