Epigenetic landscape
Epigenetic landscape is a metaphor
A metaphor is a literary figure of speech that uses an image, story or tangible thing to represent a less tangible thing or some intangible quality or idea; e.g., "Her eyes were glistening jewels." Metaphor may also be used for any rhetorical figures of speech that achieve their effects via...

 for biological development
Morphogenesis , is the biological process that causes an organism to develop its shape...

. Its originator, Conrad Hal Waddington
Conrad Hal Waddington
Conrad Hal Waddington CBE FRS FRSE was a developmental biologist, paleontologist, geneticist, embryologist and philosopher who laid the foundations for systems biology...

, said that cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

 fates were established in development much like a marble rolls down to the point of lowest local elevation
Local optimum
Local optimum is a term in applied mathematics and computer science.A local optimum of a combinatorial optimization problem is a solution that is optimal within a neighboring set of solutions...

. Waddington suggested visualising increasing irreversibility of cell type differentiation as ridges rising between the valleys where the marbles (cells) are travelling.

Today, the term refers to the combined epigenetic modifications of a given domain of DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

 sequence. Epigenetic modifications include methylation
In the chemical sciences, methylation denotes the addition of a methyl group to a substrate or the substitution of an atom or group by a methyl group. Methylation is a form of alkylation with, to be specific, a methyl group, rather than a larger carbon chain, replacing a hydrogen atom...

 of cytosine
Cytosine is one of the four main bases found in DNA and RNA, along with adenine, guanine, and thymine . It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached . The nucleoside of cytosine is cytidine...

 residues of DNA and post-translational modifications of the histone
In biology, histones are highly alkaline proteins found in eukaryotic cell nuclei that package and order the DNA into structural units called nucleosomes. They are the chief protein components of chromatin, acting as spools around which DNA winds, and play a role in gene regulation...

 proteins associated with the DNA strand. The specific combination of epigenetic modifications determines the conformation of the chromatin
Chromatin is the combination of DNA and proteins that make up the contents of the nucleus of a cell. The primary functions of chromatin are; to package DNA into a smaller volume to fit in the cell, to strengthen the DNA to allow mitosis and meiosis and prevent DNA damage, and to control gene...

 fibre into which the DNA and histones are packaged, and can thereby regulate the transcription
Transcription (genetics)
Transcription is the process of creating a complementary RNA copy of a sequence of DNA. Both RNA and DNA are nucleic acids, which use base pairs of nucleotides as a complementary language that can be converted back and forth from DNA to RNA by the action of the correct enzymes...

al potential of the underlying gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...


See also

  • Canalisation (genetics)
    Canalisation (genetics)
    Canalisation is a measure of the ability of a population to produce the same phenotype regardless of variability of its environment or genotype. In other words, it means robustness. The term canalisation was coined by C. H. Waddington...

  • Epigenetics
    In biology, and specifically genetics, epigenetics is the study of heritable changes in gene expression or cellular phenotype caused by mechanisms other than changes in the underlying DNA sequence – hence the name epi- -genetics...

  • Chreode
    Creode is a neologism coined by the biologist C.H. Waddington to represent the developmental pathway followed by a cell as it grows to form part of a specialized organ. Combining the Greek roots for "necessary" and "path," the term was inspired by the property of regulation...

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