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: