Pedigree Chart

Pedigree analysis is a family tree chart that shows which members of the family are influenced by a genetic trait. The goal of a pedigree is to facilitate an easy chart that displays a certain trait or disorder in a person.

Pedigree Chart

A pedigree chart comprising all of a family’s members can be used to show a family tree. They could be suffering from a hereditary condition or be disease carriers. Standard symbols are applied in pedigree analysis to distinguish between various families.

• Females are depicted as circles, whereas males are depicted as squares.
• Individuals with shaded symbols are affected by a condition, whereas those without shaded symbols are unaffected.
• Mating is represented as a horizontal line between a man and a woman, and the children are born as offshoots of this line

How to make and analyse pedigree chart {Procedure} 

1. Choose a family with a monogenic characteristic such as tongue rolling, blood groups, widow’s peak, or colour blindness.
2. Inquire of the person displaying the feature about who else in his or her family possesses the trait in the issue.
3. On the basis of the information gathered, create a pedigree chart with relevant symbols.
4. Determine whether the condition is autosomal recessive or dominant, X-linked dominant or recessive, or Y-linked dominant or recessive by looking at the pedigree chart.

The Function of Pedigrees

The goal of a pedigree is to facilitate an easy chart that displays a certain trait or disorder in a person. It can be used to describe a physical trait such as a widow’s peak, as well as a genetic illness such as colour blindness or Huntington’s disease. Scientists utilise pedigree analysis to analyse the inheritance of phenotypes, or traits, in numerous contexts, including different plant and animal species, utilising mating experiments termed crosses.

Dominant and Recessive Genes

To comprehend pedigrees, one must first comprehend dominant and recessive genes. Some features, like height, are controlled by a combination of genes and the environment in which an individual lives. A pedigree cannot accurately convey height. Simple dominant and recessive qualities are usually represented by pedigrees If a person possesses that trait, their pedigree sign will be shaded in.

Examples of Pedigree Chart

Autosomal Dominant

In an autosomal dominant inheritance, the gene is autosomal, which means it is located on a chromosome that is not a sex chromosome (X or Y). Because their parents were heterozygous and passed on two recessive genes to those who do not show the trait, not all of the offspring inherited the trait. The characteristic is absent in the offspring of two recessive people. 

Huntington’s disease and Marfan syndrome are examples of autosomal dominant illnesses.

Recessive Autosomal

In an autosomal recessive trait or disorder pedigree, the entirely shaded square denotes a male with the character who is homozygous recessive. And all of the half-shaded individuals are carriers; those who do not show the characteristic since it is recessive, but if their partner is also a heterozygote, they could pass it on to their offspring. 

Cystic fibrosis and Tay-Sachs disease are the two most common autosomal recessive illnesses.

Dominant X-Linked Traits

The X chromosome contains the coding gene for such traits. In this trait, the mutant allele is dominant.

These attributes have the following characteristics:

• Inheritance is a vertical phenomenon that occurs through generations.
• If a woman is affected, half of her sons are afflicted as well.
• If a guy is infected, all of his daughters are infected as well, but no sons are affected, indicating that there is no male-to-male transfer.

Examples of Dominant x-linked chromosomal disorders are Rett syndrome, X-linked lissencephaly, incontinent a pigment type 1, and double-cortex syndrome.

Recessive X-Linked Traits

In Recessive X-Linked Traits, the mutant allele is recessive to the wild type allele in several qualities. The following are characteristics of X-linked recessive The following are characteristics of X-linked recessive traits:

Not only homozygous females but also homozygous and hemizygous males, exhibit this trait.

If a girl has an affected X chromosome that is inherited by a single mutated gene from the other parent will usually cancel out the mutation’s effect, and she will most likely be free of the genetic disease. She will only be affected by the disorder if she inherits a mutant copy of the gene from both parents. Fathers cannot pass on X-linked recessive disorders to their sons. The genetic disorder is more likely to arise when a son receives a defective gene on the X chromosome from his mother. Males are more likely than females to have X-linked recessive disorders.

Examples of X-linked recessive chromosomal disorders are colorblindness and haemophilia A.

Y-linked chromosomal Traits

On the Y-chromosome, a gene for these features can be found. Because the Y-chromosome is only present in males, any attribute associated with it can only be detected in them. The feature is present in all of the affected man’s sons, but not in any of his daughters.

Examples of Y-linked chromosomal disorders are Hypertrichosis of the ears, webbed toes, and porcupine man.

Conclusion

Because the usual lines and split lines (each split going to separate offspring of the same parent line) resemble the slender leg and foot of a crane, the word pedigree is a corruption of the Anglo-Norman French pé de grue, or “crane’s foot,” which was used to denote succession on pedigree charts. A pedigree is a graph that shows family information in an easy-to-follow format. A “family tree” is how most people refer to it. In pedigrees, a standard set of symbols is utilised, with squares representing men and circles representing women. The construction of a pedigree is a family history, and as memories fade, details about prior generations may become vague. If the person’s sex is unknown, a diamond is utilised. Someone who has the trait in question is represented by a filled-in (darker) symbol. When heterozygotes are recognized, they are indicated by a shaded dot inside a symbol or a half-filled sign.