Karyotype and Pedigree Analysis- “Do they differ?”

Genetics is a branch of science that deals with the arrangement, expression and interaction of genes present on chromosomes which reflects as a specific morphologic trait in living organisms. Within the domain of Genetics; Karotype analysis and Pedigree analysis provide important clinical and physiological information regarding the probability of occurrence of a particular malfunction and helps in diagnosis and management of diseases.  Karyotype refers to the study of chromosome number and appearance of chromosomes which are present within the nucleus of a cell. Further the complete set of chromosomes in a species or a particular organism is also referred to as Karyotype. A karyotype is represented in a standard format as a karyogram or idiogram with respect to the pairing of homologous or non homologous chromosomes, arrangement of chromosomes according to size and providing information of the position of centromere through pictorial (photo micrographic) depictions.

Karyotyping is useful for the study of cell biology and genetics and the results are used for interpreting evolutionary trends. It is also important to study chromosomal aberrations (abnormalities in number and shape of chromosomes), cellular functions, and taxonomic relationships. Karyotype can indicate the difference in absolute and relative size of chromosomes in an individual or closely related species, position of the centromeres and satellites, differences in the degree and distribution of heterechromatin and euchromatin regions in individual chromosomes. Karyotype differs between sexes, germ line cells and somatic cells, and also between members of the same population.

Pedigree analysis is a visual representation of a particular trait amongst members (descendants) of the same family. Such analysis is usually done for three generations or even more. The crosses between the male and female (marriage) are represented by lines and the genders male is represented as a box while females are represented as circles. The presence of particular trait in any respective individuals is represented in black.  The analysis is used to determine the mode of inheritance of a specific trait. This means the trait can be classified as dominant, recessive and also it can be extrapolated whether such dominant or recessive trait resides on the sex chromosomes (allosomes) or somatic chromosomes (autosomes). On that basis the trait may be classified as autosomal dominant or autosomal recessive and sex-linked dominant or sex-linked recessive. The basis of pedigree analysis is dependent on the Mendel’s laws of independent assortment and law of segregation.  Pedigree analysis is very useful to predict a trait in subsequent generation, through probability testing. This helps to identify situations like haemophilia or colour blindness well in advance, even before the generation appears.

A comparison of Karyotype and Pedigree analysis is described as follows:

Features	Karyotype	Pedigree Analysis
Represented	Photo micrographic details of chromosomes, in terms of number, size and detailed position of satellites and centromeres	Visual depiction of relationships and appearance of trait in generations of a family
Visual depictions	As per the real morphology of the chromosomes	Shapes, sizes and lines are represented to denote gender and marriage and descendants
Schematic analysis	No	Yes
Study of	Chromosomes	Traits or character
Principle	Based on pictorial depictions and are not based on laws of heredity	Based on Mendel’s laws of Heredity
Speculations	No speculationsActual and real time analysis	Speculations and are based on both laws of heredity and probability
Providing details of macro satellites or microsatellites	Yes	Never
Disease Predictions in subsequent generations	No	Yes
Study of genes	No	Yes
Chromosomal aberrations	Can be revealed	Cannot be revealed
Classification through autosomes or allosomes	Not possible	Always possible
Analysis of Genetic Diseases	No	Yes
Providing information about Cellular dysfunction	Yes, from the study of chromosome morphology	No, because it does not reveals cellular details.
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