Deoxyribonucleic acid (DNA) is a nucleic acid which carries genetic instructions for the biological development of all cellular forms of life and many viruses. DNA is sometimes referred to as the molecule of heredity as it is inherited and used to propagate traits. During reproduction, it is replicated and transmitted to offspring.
In bacteria and other simple cell organisms, DNA is distributed more or less throughout the cell. In the complexEukaryotes are organisms with complex cells, in which the genetic material is organized into membrane-bound nuclei. They include the animals, plants, and fungi, which are mostly multicellular, as well as various other groups called protists, many of which cells that make up plantGreen algae land plants (embryophytes non-vascular embryophytes Hepatophyta liverworts Anthocerophyta hornworts Bryophyta mosses vascular plants (tracheophytes seedless vascular plants Lycopodiophyta clubmosses Equisetophyta horsetails Pteridophyta "true"s, animalSubkingdom Parazoa Porifera (sponges) Subkingdom " Agnotozoa" Placozoa Orthonectida Rhombozoa Subkingdom Metazoa "Radiata" Cnidaria Ctenophora (comb jellies) Bilateria Protostomia Acoelomorpha Platyhelminthes (flatworms) Nemertina (ribbon worms) Gastrotris and in other multi-celled organismIn biology and ecology, an organism is a living being. The origin of life and the relationships between its major lineages are controversial. Two main grades may be distinguished, the prokaryotes and eukaryotes. The prokaryotes are generally considered tos, most of the DNA is found in the chromosome2) Centromere. The point where the two chromatids touch, and where the microtubules attach. 3) Short arm. 4) Long arm. A chromosome is, minimally, a very long, continuous piece of DNA, which contains many genes, regulatory elements and other intervening ns, which are located in the cell nucleusIn cell biology, the nucleus is an organelle, found in most eukaryotic cells, which contains most of the cell's genetic material. Nuclei have two primary functions: to control chemical reactions within the cytoplasm and to store information needed for cel. The energy-generating organelleIn cell biology, an organelle is one of several structures with specialized functions, suspended in the cytoplasm of a eukaryotic cell. Organelles were historically identified through the use of some form of microscopy and were also identified through thes known as chloroplastChloroplasts are organelles found in plant cells and eukaryotic algae which conduct photosynthesis. Chloroplasts are similar to mitochondria but are found only in plants. Both organelles are surrounded by a double membrane with an intermembrane space; bots and mitochondria also carry DNA, as do many viruses.
1 DNA in brief
This section presents an overview of DNA.
- Disclaimer: This section is an overview of DNA in brief suitable for the lay reader, without detailed information. It is intended to serve as an introduction to the topic. More details are found in the rest of the main text.
- Genes can be loosely viewed as the organism's "cookbook";
- A strand of DNA contains genes, areas that regulate genes, and areas that either have no function, or a function we don't know;
- DNA is organized as two complementary strands, head-to-toe, with bonds between them that can be "unzipped" like a zipper, separating the strands;
- DNA is encoded with four interchangeable "building blocks", called " bases", which can be abbreviated A, T, C, and G; each base "pairs up" with only one other base: A+T, T+A, C+G and G+C; that is, an "A" on one strand of double-stranded DNA will "mate" properly only with a "T" on the other, complementary strand;
- The order does matter: A+T is not the same as T+A, just as C+G is not the same as G+C;
- However, since there are just four possible combinations, naming only one base on the conventionally chosen side of the strand is enough to describe the sequence;
- The order of the bases along the length of the DNA is what it's all about, the sequence itself is the description for genes;
- Replication is performed by splitting (unzipping) the double strand down the middle via relatively trivial chemical reactions, and recreating the "other half" of each new single strand by drowning each half in a "soup" made of the four bases. Since each of the "bases" can only combine with one other base, the base on the old strand dictates which base will be on the new strand. This way, each split half of the strand plus the bases it collects from the soup will ideally end up as a complete replica of the original, unless a mutation occurs;
- Mutations are simply chemical imperfections in this process: a base is accidentally skipped, inserted, or incorrectly copied, or the chain is trimmed, or added to; all other basic mutations can be described as combinations of these accidental "operations".
