A pedigree chart is a diagram that shows the occurrence and appearance of

phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (biology), morphology or physical form and structure, its Developmental biology, developmental proc ...

s of a particular gene or

organism In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells ( cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and fu ...

and its

ancestor An ancestor, also known as a forefather, fore-elder or a forebear, is a parent or ( recursively) the parent of an antecedent (i.e., a grandparent, great-grandparent, great-great-grandparent and so forth). ''Ancestor'' is "any person from w ...

s from one generation to the next, most commonly

humans" \n\n\n\n\nThe robots exclusion standard, also known as the robots exclusion protocol or simply robots.txt, is a standard used by websites to indicate to visiting web crawlers and other web robots which portions of the site they are allowed to visi ...

, show dogs, and race

horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million yea ...

Definition

The word pedigree is a corruption of the Anglo-Norman French ''pé de grue'' or "crane's foot", either because the typical lines and split lines (each split leading to different offspring of the one parent line) resemble the thin leg and foot of a crane or because such a mark was used to denote succession in pedigree charts. A pedigree results in the presentation of family information in the form of an easily readable chart. It can be simply called as a "family tree". Pedigrees use a standardized set of symbols, squares represent males and circles represent females. Pedigree construction is a family history, and details about an earlier generation may be uncertain as memories fade. If the sex of the person is unknown a diamond is used. Someone with the phenotype in question is represented by a filled-in (darker) symbol. Heterozygotes, when identifiable, are indicated by a shade dot inside a symbol or a half-filled symbol. Relationships in a pedigree are shown as a series of lines. Parents are connected by a horizontal line and a vertical line leads to their offspring. The offspring are connected by a horizontal sibship line and listed in birth order from left to right. If the offspring are twins then they will be connected by a triangle. If an offspring dies then its symbol will be crossed by a line. If the offspring is still born or aborted it is represented by a small triangle. Each generation is identified by a

Roman numeral Roman numerals are a numeral system that originated in ancient Rome and remained the usual way of writing numbers throughout Europe well into the Late Middle Ages. Numbers are written with combinations of letters from the Latin alphabet, ea ...

(I, II, III, and so on), and each individual within the same generation is identified by an

Arabic numeral Arabic numerals are the ten numerical digits: , , , , , , , , and . They are the most commonly used symbols to write decimal numbers. They are also used for writing numbers in other systems such as octal, and for writing identifiers such as ...

(1, 2, 3, and so on). Analysis of the pedigree using the principles of Mendelian inheritance can determine whether a trait has a dominant or recessive pattern of inheritance. Pedigrees are often constructed after a family member afflicted with a genetic disorder has been identified. This individual, known as the proband, is indicated on the pedigree by an arrow. These changes may occur yearly or monthly. File:Wiki Drawing - Y-Linked (1).svg, In a Y-linked disorder, only males can be affected. If the father is affected all sons will be affected. It also does not skip a generation. File:Wiki Drawing - Mitochondrial.svg, In mitochondrial disorders it is only passed on if the mother is affected. If the mother is affected, all offspring will be affected. If the father is affected, he does not pass it on to his offspring. File:Wiki Drawing - Autosomal Recessive (2).svg, In an autosomal recessive disorder, both parents can not express the trait, however, if both are carriers, their offspring can express the trait. Autosomal recessive disorders typically skip a generation, so affected offspring typically have unaffected parents. With an autosomal recessive disorder, both males and females are equally likely to be affected. File:Wiki Drawing - Autosomal Dominant (1).svg, Autosomal dominant disorders do not skip a generation, so affected offspring have affected parents. One parent must have the disorder for its offspring to be affected. Both males and females are equally likely to be affected, so it is an autosomal disorder. File:Wiki Drawing - X-Linked Recessive (1).svg, In a X-linked recessive disorder, males are more likely to be affected than females. Affected sons typically have unaffected mothers. The father also must be affected for daughter to be affected and the mother must be affected or a carrier for the daughter to be affected. The disorder is also never passed from father to son. Only females can be carriers for the disorders. X-linked recessive disorders also typically skip a generation. File:Wiki Drawing - X-Linked Dominant (1).svg, In a X-Linked dominant disorder, if the father is affected all daughters will be affected and no sons will be affected. It does not skip a generation and if the mother is affected she has a 50% chance of passing it onto her offspring.

In human use

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe ...

and

Wales Wales ( cy, Cymru ) is a country that is part of the United Kingdom. It is bordered by England to the east, the Irish Sea to the north and west, the Celtic Sea to the south west and the Bristol Channel to the south. It had a population in ...

pedigrees are officially recorded in the

College of Arms The College of Arms, or Heralds' College, is a royal corporation consisting of professional officers of arms, with jurisdiction over England, Wales, Northern Ireland and some Commonwealth realms. The heralds are appointed by the British Sover ...

, which has records going back to the Middle Ages, including pedigrees collected during roving inquiries by its heralds during the sixteenth and seventeenth centuries. The purpose of these heraldic visitations was to register and regulate the use of

coats of arms A coat of arms is a heraldic visual design on an escutcheon (i.e., shield), surcoat, or tabard (the latter two being outer garments). The coat of arms on an escutcheon forms the central element of the full heraldic achievement, which in i ...

. Those who claimed the right to bear arms had to provide proof either of a grant of arms to them by the College, or of descent from an ancestor entitled to arms. It was for this reason that pedigrees were recorded by the visitations. Pedigrees continue to be registered at the College of Arms and kept up to date on a voluntary basis but they are not accessible to the general public without payment of a fee. More visible, therefore, are the pedigrees recorded in published works, such as

Burke's Peerage Burke's Peerage Limited is a British genealogical publisher founded in 1826, when the Irish genealogist John Burke began releasing books devoted to the ancestry and heraldry of the peerage, baronetage, knightage and landed gentry of Great ...

and Burke's

Landed Gentry The landed gentry, or the ''gentry'', is a largely historical British social class of landowners who could live entirely from rental income, or at least had a country estate. While distinct from, and socially below, the British peerage, t ...

in the United Kingdom and, in continental

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

by the

Almanach de Gotha The ''Almanach de Gotha'' (german: Gothaischer Hofkalender) is a directory of Europe's royalty and higher nobility, also including the major governmental, military and diplomatic corps, as well as statistical data by country. First publish ...

. A pedigree may be used to establish the probability of a child having a particular disorder or condition. It may be used to discover where the genes in question are located (x, y, or autosome chromosome), and to determine whether a trait is dominant or recessive. When a pedigree shows a condition appearing in a 50:50 ratio between men and women it is considered

autosomal An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosomal (sex chromosome) pairs, which may have different structures. The DNA in autosom ...

. When the condition predominantly affects males in the pedigree it is considered x-linked. Some examples of dominant traits include: male baldness,

astigmatism Astigmatism is a type of refractive error due to rotational asymmetry in the eye's refractive power. This results in distorted or blurred vision at any distance. Other symptoms can include eyestrain, headaches, and trouble driving at n ...

, and

dwarfism Dwarfism is a condition wherein an organism is exceptionally small, and mostly occurs in the animal kingdom. In humans, it is sometimes defined as an adult height of less than , regardless of sex; the average adult height among people with dw ...

. Some examples of recessive traits include: small eyes, little body hair, and tall stature.

In animal husbandry

In the practice of

selective breeding Selective breeding (also called artificial selection) is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant ...

of animals, particularly in animal fancy and

livestock Livestock are the domesticated animals raised in an agricultural setting to provide labor and produce diversified products for consumption such as meat, eggs, milk, fur, leather, and wool. The term is sometimes used to refer solely to ani ...

, including

s, pedigree charts are used to track the ancestry of animals and assist in the planning of suitable breeding programs to enhance desirable traits.

Breed registries A breed registry, also known as a herdbook, studbook or register, in animal husbandry and the hobby of animal fancy, is an official list of animals within a specific breed whose parents are known. Animals are usually registered by their breeder ...

are formed and are dedicated to the accurate tracking of pedigrees and maintaining accurate records of birth, death and identifying characteristics of each registered animal.

References

{{Family Classical genetics Diagrams Family trees

Definition

In human use

In animal husbandry

See also

References