Biological inheritance is the process by which an offspring cell or organism acquires or becomes predisposed to characteristics of its parent cell or organism. Through inheritance, variations exhibited by individuals can accumulate and cause a species to evolve. Drawing of the structure of cork as it appeared under the microscope to Robert Hook from Micrographia which is the origin of the word cell. Cells in culture, stained for keratin (red) and DNA (green). ... A crab is an example of an organism. ... In biology, a species is one of the basic units of biodiversity. ... In 1832, while travelling on the Beagle, naturalist Charles Darwin collected giant fossils in South America. ...

The study of biological inheritance is called genetics, which includes epigenetics. Genetics (from the Greek genno γεννώ= give birth) is the science of genes, heredity, and the variation of organisms. ... Epigenetics is the study of reversible heritable changes in gene function that occur without a change in the sequence of nuclear DNA. It is also the study of the processes involved in the unfolding development of an organism. ...

The description of a mode of biological inheritance consists of three main categories:

• 1. Number of involved Loci

-Monogenetic (also called "simple") - one Locus

-Oligogenetic - few Loci

-Polygenetic - many Loci

• 2. Involved Chromosomes

-Autosomal - Loci are not situated on a sex chromosome

-Gonosomal - Loci are situated on a sex chromosome

-X-Chromosomal - Loci are situated on the X chromosome (the more common case)

-Y-Chromosomal - Loci are situated on the Y chromosome

-Mitochondrial - Loci are situated on the mitochondrial DNA

• 3. Correlation genotype-phenotype

-Dominant

-Intermediate (also called "codominant")

-Recessive

These three categories are part of every ecact description of a mode of inheritance in the above order. Additionally, more specifications may be added as follows: In biology and evolutionary computation, a locus is the position of a gene (or other significant sequence) on a chromosome. ... This does not cite its references or sources. ... In biology and evolutionary computation, a locus is the position of a gene (or other significant sequence) on a chromosome. ... It has been suggested that this article or section be merged into quantitative trait locus. ... Figure 1: Chromosome. ... An autosome is a non-sex chromosome. ... A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. ... A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. ... The X chromosome is one of the two sex-determining chromosomes in many animal species, including mammals (the other is the Y chromosome). ... The human Y chromosome is one of two sex chromosomes, it contains the genes that cause testis development, thus determining maleness. ... ... // Mitochondrial DNA (mtDNA) is DNA that is located in mitochondria. ... The genotype is the specific genetic makeup (the specific genome) of an individual, in the form of DNA. Together with the environmental variation that influences the individual, it codes for the phenotype of that individual. ... Individuals in the mollusk species Donax variabilis show diverse coloration and patterning in their phenotypes. ... The word dominant has several possible meanings: In music theory, the dominant or dominant note (second most important) of a key is that which is a perfect fifth above the tonic; in just intonation the note whose pitch is 1. ... In chemistry a reactive intermediate is a short-lived high energy highly reactive molecule. ... In genetics, the term recessive gene refers to an allele that causes a phenotype (visible or detectable characteristic) that is only seen in a homozygous genotype (an organism that has two copies of the same allele). ...

• Coincidental and environmental interactions

-Penetrance

-Complete

-Incomplete (percentual number)

-Expressivity

-Invariable

-Variable

-Heritability (in polygenetic and sometimes also in oligogenetic modes of inheritance)

-Maternal or paternal imprinting phenomena (also see epigenetics)

• Gender interactions

-Sex-linked inheritance (Gonosomal Loci)

-Sex-limited phenotype expression (e.g. Cryptorchism)

-Inheritance through the maternal line (in case of Mitochondrial DNA loci)

-Inheritance through the paternal line (in case of Y-chromosomal loci)

• Locus-Locus-Interactions

-Epistasis with other Loci (e.g. overdominance)

-Gene coupling with other Loci (also see Crossing over)

-Homozygotous lethal factors

-Semi-lethal factors

Determination and description of a mode of inheritance is primarily achieved through statistical analysis of pedigree data. In case the involved loci are known, methods of molecular genetics can also be employed. Penetrance is a term used in genetics that describes the extent to which the properties controlled by a gene, its phenotype, will be expressed. ... Expressivity refers to variations of a phenotype in genetics. ... Heritability, as used professionally in genetics, has a very precise definition. ... Genomic imprinting is the phenomenon whereby a small subset of all the genes in the genome are expressed according to their parent of origin. ... Epigenetics is the study of reversible heritable changes in gene function that occur without a change in the sequence of nuclear DNA. It is also the study of the processes involved in the unfolding development of an organism. ... During male mammalian development, the testes normally descend from their original position in the abdomen to their final home, the scrotum. ... // Mitochondrial DNA (mtDNA) is DNA that is located in mitochondria. ... The human Y chromosome is one of two sex chromosomes, it contains the genes that cause testis development, thus determining maleness. ... Epistasis takes place when the action of one gene is modified by one or more others that assort somewhat independently. ... Overdominance describes a genetic relationship between two alleles when the phenotype of the heterozygote is greater than that of either homozygote. ... Chromosomal crossover is the process by which two chromosomes, paired up during Prophase I of meiosis, exchange some distal portion of their DNA. Crossover occurs when two chromosomes, normally two homologous instances of the same chromosome, break and then reconnect but to the different end piece. ... Molecular genetics is the field of biology which studies the structure and function of genes at a molecular level. ...

Literature

Ruvinsky and Simpson (2001) The Genetics of the Dog; CABI Publishing, Wallingford/New York.

Srb, Owen and Edgar (1965) General Genetics; Freeman & Company, San Francisco.