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Diagram of a typical prokaryotic cell. A prokaryote (/ p r oʊ ˈ k ær i oʊ t,-ə t /; less commonly spelled procaryote) [1] is a single-cell organism whose cell lacks a nucleus and other membrane-bound organelles. [2] The word prokaryote comes from the Ancient Greek πρό (pró), meaning 'before', and κάρυον (káruon), meaning 'nut ...
Gene structure is the organisation of specialised sequence elements within a gene. Genes contain most of the information necessary for living cells to survive and reproduce. [1][2] In most organisms, genes are made of DNA, where the particular DNA sequence determines the function of the gene. A gene is transcribed (copied) from DNA into RNA ...
Category. v. t. e. Cell biology (also cellular biology or cytology) is a branch of biology that studies the structure, function, and behavior of cells. [1][2] All living organisms are made of cells. A cell is the basic unit of life that is responsible for the living and functioning of organisms. [3] Cell biology is the study of the structural ...
The cell cycle in eukaryotes: I = Interphase, M = Mitosis, G 0 = Gap 0, G 1 = Gap 1, G 2 = Gap 2, S = Synthesis, G 3 = Gap 3. Cell division is the process by which a parent cell divides into two daughter cells. [1] Cell division usually occurs as part of a larger cell cycle in which the cell grows and replicates its chromosome (s) before dividing.
They are simpler and smaller than eukaryotic cells, and lack a nucleus, and other membrane-bound organelles. The DNA of a prokaryotic cell consists of a single circular chromosome that is in direct contact with the cytoplasm. The nuclear region in the cytoplasm is called the nucleoid. Most prokaryotes are the smallest of all organisms, ranging ...
The principal forces of evolution in prokaryotes and their effects on archaeal and bacterial genomes. The horizontal line shows archaeal and bacterial genome size on a logarithmic scale (in megabase pairs) and the approximate corresponding number of genes (in parentheses).The effects of the main forces of prokaryotic genome evolution are denoted by triangles that are positioned, roughly, over ...
Polysome. Several ribosomes synthesizing a polypeptide on the same mRNA strand. A polyribosome (or polysome or ergosome) is a group of ribosomes bound to an mRNA molecule like “beads” on a “thread”. [1] It consists of a complex of an mRNA molecule and two or more ribosomes that act to translate mRNA instructions into polypeptides.
The split gene theory is a theory of the origin of introns, long non-coding sequences in eukaryotic genes between the exons. [1] [2] [3] The theory holds that the randomness of primordial DNA sequences would only permit small (< 600bp) open reading frames (ORFs), and that important intron structures and regulatory sequences are derived from stop codons.