Individuals in the mollusk species Donax variabilis show diverse coloration and patterning in their phenotypes. Molluscs are animals belonging to the phylum Mollusca. There are around 250000 extant Species within the phylum with an estimated 70000 Donax is a Genus of small edible saltwater clams marine Bivalve Mollusks The genus is sometimes known as bean clams

A phenotype is any observable characteristic of an organism, such as its morphology, development, biochemical or physiological properties, or behavior. The term morphology in Biology refers to the outward appearance ( Shape, Structure, Colour, Pattern) of an Organism Behavior or behaviour (see spelling differences) refers to the actions or Reactions of an object or Organism, usually Phenotypes are influenced by a combination of genetic and environmental factors. This contrasts with the genotype of an organism - the inherited instructions it carries - which may or may not cause an observable effect on the organism. The genotype is the genetic constitution of a cell an organism or an individual (i This genotype-phenotype distinction was proposed by Wilhelm Johannsen in 1911 to make clear the difference between an organism's heredity and what that heredity produces. The genotype-phenotype distinction is drawn in Genetics. " Genotype " is an organism's full Hereditary information even if not expressed Wilhelm Johannsen ( February 3, 1857 - November 11, 1927) was a Danish Botanist, plant physiologist and Geneticist ^[1][2] The distinction is similar to that proposed by August Weismann, who distinguished between germ plasm (heredity) and somatic cells (the body). Friedrich Leopold August Weismann (Birth January 17, 1834 in Frankfurt am Main; Death Germ plasm or polar plasm is a zone found in the cytoplasm of the Egg cells of some Model organisms (such as Caenorhabditis elegans Somatic cells are any cells forming the body of an organism as opposed to Germline cells A more modern version is Francis Crick's Central dogma of molecular biology. Francis Harry Compton Crick OM FRS (8 June 1916 – 28 July 2004 Ph The central dogma of molecular biology was first enunciated by Francis Crick in 1958 and re-stated in a Nature paper published in 1970

Despite its seemingly straightforward definition, the concept of the phenotype has some hidden subtleties. First, most of the molecules and structures coded by the genetic material are not visible in the appearance of an organism, yet they are observable (for example by Western blotting) and are thus part of the phenotype. The western blot (alternatively immunoblot) is an Analytical technique used to detect specific Proteins in a given sample of tissue homogenate or Human blood groups are an example. A blood type (also called a blood group) is a classification of Blood based on the presence or absence of inherited Antigenic substances on the So, by extension, the term phenotype must include characteristics that can be made visible by some technical procedure. A further, and more radical, extension would add behaviour to the phenotype since behaviours are also affected by both genotypic and environmental factors.

Biston betularia morpha typica, the standard light-coloured Peppered Moth.

Biston betularia morpha carbonaria, the melanic Peppered Moth, illustrating discontinuous variation.

Second, the phenotype is not simply a product of the genotype, but is influenced by the environment to a greater or lesser extent (see also phenotypic plasticity). The ability of an organism with a given Genotype to change its Phenotype in response to changes in the environment is called phenotypic plasticity. And, further, if the genotype is defined narrowly, then it must be remembered that not all heredity is carried by the nucleus. In Cell biology, the nucleus (pl nuclei; from Latin la ''nucleus'' or la ''nuculeus'' "little nut" or kernel is a membrane-enclosed For example, mitochondria transmit their own DNA directly, not via the nucleus, though they divide in unison with the nucleus. In Cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed Organelle found in most eukaryotic cells. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known

The phenotype is composed of traits or characteristics ^[3]. A trait is a distinct phenotypic character of an organism that may be inherited environmentally determined or somewhere in between Some phenotypes are controlled entirely by the individual's genes. History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance Others are controlled by genes but are significantly affected by extragenetic or environmental factors. Almost all humans inherit the capacity to speak and understand language, but which language they learn is entirely an environmental matter.

Phenotypic variation

Phenotypic variation (due to underlying heritable genetic variation) is a fundamental prerequisite for evolution by natural selection. Genetic diversity is a level of Biodiversity that refers to the total number of genetic characteristics in the genetic makeup of a species eVolution is the third Album by eLDee, it was due to be released in 2008 Natural selection is the process by which favorable Heritable traits become more common in successive Generations of a Population of It is the living organism as a whole that contributes (or not) to the next generation, so natural selection affects the genetic structure of a population indirectly via the contribution of phenotypes. Without phenotypic variation, there would be no evolution by natural selection.

The interaction between genotype and phenotype has often been conceptualized by the following relationship:

genotype + environment → phenotype

A slightly more nuanced version of the relationships is:

genotype + environment + random-variation → phenotype

An example of random variation in Drosophila flies is the number of ommatidia, which may vary (randomly) between left and right eyes in a single individual as much as they do between different genotypes overall, or between clones raised in different environments. Drosophila is a Genus of small flies, belonging to the family Drosophilidae, whose members are often called "fruit flies" The Compound eye of Insects is composed of units called ommatidia. Cloning in Biology is the process of producing populations of genetically-identical individuals that occurs in nature when organisms such as Bacteria, Insects

A phenotype is any detectable characteristic of an organism (i. e. , structural, biochemical, physiological, and behavioral) determined by an interaction between its genotype and environment (of this distinction).

According to the autopoietic notion of living systems by Humberto Maturana, the phenotype is epigenetically being constructed throughout ontogeny, and we as observers make the distinctions that define any particular trait at any particular state of the organism's life cycle. Autopoiesis literally means "auto (self-creation" (from the Greek: auto αυτό for self- and poiesis ποίησις for creation or production Humberto Maturana (born September 14, 1928, in Santiago Chile) is a Chilean Biologist. Ontogeny, as opposed to Phylogeny, refers to the history of an organism from birth as opposed to its genetic makeup

The idea of the phenotype has been generalized by Richard Dawkins in The Extended Phenotype to mean all the effects a gene has on the outside world that may influence its chances of being replicated. Clinton Richard Dawkins, FRS, FRSL (born 26 March 1941 is a British ethologist, evolutionary biologist, and Popular science The Extended Phenotype (subtitled "The Gene as the Unit of Selection" and later "The Long Reach of the Gene" is a 1982 book by Richard These can be effects on the organism in which the gene resides, the environment, or other organisms. For instance, a beaver dam might be considered a phenotype of beaver genes, the same way beaver's powerful incisor teeth are phenotype expressions of their genes. Beavers are two primarily nocturnal semi-aquatic species of Rodent, one native to North America and one to Europe Beavers are two primarily nocturnal semi-aquatic species of Rodent, one native to North America and one to Europe History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance Incisors (from Latin incidere, "to cut" are the first kind of Tooth in Heterodont Mammals They are located in the Premaxilla

The concept of phenotype can be extended to variations below the level of the gene that affect an organism's fitness. For example, silent mutations that do not change the corresponding amino acid sequence of a gene may change the frequency of guanine-cytosine base pairs (GC content). Silent mutations are DNA Mutations that do not result in a change to the Amino acid sequence of a Protein. Guanine is one of the five main Nucleobases found in the Nucleic acids DNA and RNA, the others being Adenine, Cytosine, Cytosine is one of the five main bases found in DNA and RNA. It is a Pyrimidine derivative with a Heterocyclic Aromatic ring GC-content (or guanine-cytosine content in molecular biology is the percentage of Nitrogenous bases on a DNA molecule which are either Guanine or These base pairs have a higher thermal stability (melting point, see also DNA-DNA hybridization) than adenine-thymine, a property that might convey, among organisms living in high-temperature environments, a selective advantage on variants enriched in GC content. DNA-DNA hybridization generally refers to a Molecular biology technique that measures the degree of genetic similarity between pools of DNA sequences Adenine is a Purine with a variety of roles in Biochemistry including Cellular respiration, in the form of both the energy-rich Adenosine Thymine is one of the four bases in the Nucleic acid of DNA that make up the letters ATGC

References

1. ^ Churchill F. B. 1974. William Johannsen and the genotype concept. J History of Biology 7, 5-30.
2. ^ Johannsen W. 1911. The genotype conception of heredity. American Naturalist 45, 129-159
3. ^ Sydney Brenner and Jeffrey H. Miller. 2002. Encyclopedia of Genetics San Diego: Academic Press.

See also

• Phenome
• Genotype