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This is an image of Bob, the guinea pig. Credit: selbst.

Genetics involves the expression, transmission, and variation of inherited characteristics.

Genetics studies how living organisms inherit features from their ancestors; for example, children often look like their parents. Genetics seeks to identify which features are inherited, and explain how these features are passed from generation to generation.

In genetics, a feature of an organism is called a "trait". Some traits are features of an organism's morphology or physical appearance; for example, a person's eye-color, height or weight. There are many other trait types, and these range from aspects of behavior to resistance to disease. Traits are often inherited, for example tall and thin people tend to have tall and thin children. Other traits come from the interaction between inherited features and the environment. For example a child might inherit the tendency to be tall, but if little food is available and the child is poorly nourished, it will still be short. The way genetics and environment interact to produce a trait can be complicated: for example, the chances of somebody dying of cancer or heart disease seem to depend on both their family history and their lifestyle.

Genetic information is carried by a long molecule called DNA which is copied and inherited across generations. Traits are carried in DNA as instructions for constructing and operating an organism. These instructions are contained in segments of DNA called genes. DNA is made of a sequence of simple units, with the order of these units spelling out instructions in the genetic code. This is similar to the order of letters spelling out words. The organism "reads" the sequence of these units and decodes the instruction.

Not all the genes for a particular instruction are exactly the same. Different forms of one type of gene are called different alleles of that gene. As an example, one allele of a gene for hair color could carry the instruction to produce a lot of the pigment in black hair, while a different allele could give a garbled version of this instruction, so that no pigment is produced and the hair is white. Mutations are random events that change the sequence of a gene and therefore create a new allele. Mutations can produce a new trait, such as turning an allele for black hair into an allele for white hair. The appearance of new traits is important in evolution.


Def. gene "transmission of the physical and [genetic] qualities of parents to their offspring; the biological law by which living beings tend to repeat their characteristics in their descendants"[1] is called heredity.


Def. the "appearance of an organism based on a multifactorial combination of genetic traits and environmental factors, especially used in pedigrees"[2] is called a phenotype.

Theory of genetics[edit]

This guinea pig has gorgeous long hair and was a prize winner at the Puyallup, WA fair. Credit: Christine from Washington State, USA.

Def. a "branch of biology that deals with the transmission and variation of inherited characteristics, in particular chromosomes and DNA"[3] is called genetics.

Evolutionary genetics[edit]

Molecular genetics[edit]

Def. a "field of biology which studies the structure and function of genes at a molecular level"[4] is called molecular genetics.


Def. a "science that combines optics and genetics to probe neural circuits"[5] is called optogenetics.

Population genetics[edit]

Def. the "study of the allele frequency distribution and change under the influence of the four evolutionary processes: natural selection, genetic drift, mutation and gene flow"[6] is called population genetics.

Quantitative genetics[edit]


This is a schematic representation of a nucleosome. Credit: Zephyris.
The flow chart shows recommendations for the design and analysis of epigenome-wide association studies. Credit: BLASToize.

Epigenetics is the study of genome or epigenome changes resulting from external rather than genetic influences.

Inside each eukaryote nucleus is genetic material (DNA) surrounded by protective and regulatory proteins. These protective and regulatory proteins and the dynamic changes to them that occur during the course of a eukaryote's existence are the epigenome.

Changes to the epigenome can result in changes to the structure of chromatin and changes to the function of the genome.[7]

There are "nearly 50,000 acetylated sites [punctate sites of modified histones] in the human genome that correlate with active transcription start sites and CpG islands and tend to cluster within gene-rich loci."[7]


This is a spectral karyotype (SKY) of a human female. Credit: National Human Genome Research Institute, USA.

Cytogenetics is a study of structure, function, behavior and pathology of chromosomes.

Reverse genetics[edit]

Avian Flu vaccine development was by Reverse Genetics techniques. Courtesy: National Institute of Allergy and Infectious Diseases.

Reverse genetics is an approach to discovering the function of a gene by analyzing the phenotypic effects of specific gene sequences obtained by DNA sequencing. This investigative process proceeds in the opposite direction of so-called forward genetic screens of classical genetics. Simply put, while forward genetics seeks to find the genetic basis of a phenotype or trait, reverse genetics seeks to find what phenotypes arise as a result of particular genes.

Automated DNA sequencing generates large volumes of genomic sequence data relatively rapidly. Many genetic sequences are discovered in advance of other, less easily obtained, biological information. Reverse genetics attempts to connect a given genetic sequence with specific effects on the organism.


  1. Individual breeding preferences coupled with geographical isolation may produce new species.
  2. Cavia porcellus may be derived from Cavia tschudii.

See also[edit]


  1. Poccil (20 October 2004). heredity. San Francisco, California: Wikimedia Foundation, Inc. Retrieved 2016-10-04.
  2. phenotype. San Francisco, California: Wikimedia Foundation, Inc. 12 September 2016. Retrieved 2016-10-04.
  3. genetics. San Francisco, California: Wikimedia Foundation, Inc. April 16, 2014. Retrieved 2014-05-07.
  4. Pumpie (27 August 2005). molecular genetics. San Francisco, California: Wikimedia Foundation, Inc. Retrieved 2016-01-09.
  5. optogenetics. San Francisco, California: Wikimedia Foundation, Inc. January 30, 2014. Retrieved 2014-05-07.
  6. population genetics. San Francisco, California: Wikimedia Foundation, Inc. August 18, 2009. Retrieved 2014-05-07.
  7. 7.0 7.1 Bradley E. Bernstein, Alexander Meissner, Eric S. Lander (February 23, 2007). "The Mammalian Epigenome". Cell 128 (4): 669–81. doi:10.1016/j.cell.2007.01.033. http://www.sciencedirect.com/science/article/pii/S0092867407001286. Retrieved 19 December 2011. 

External links[edit]