Question

Explain why man is unsuitable material for genetic experimentation and how geneticist studied the inheritance in man?

Answer 1

• Though, man has many well contrasted variations and he always reproduces sexually, but desired controlled matings for genetical purpose are not possible due to social and ethical reasons.
• Therefore, he is not a suitable material for genetic experimentation.
• Further, he has a long generation or life-cycle, produces extremely small number of offspring and difficult to handle in laboratory conditions.
• Inspite of these negative characters in his favor, much has been learned about the genetics of man by various cytological and genetical techniques.

The pedigree analysis is such a technique which has been most commonly used by human geneticists.

Pedigree analysis:

• By the method of pedigree analysis, the studies of traits as they have appeared in a given family line for several past generations.
• For example, in following figure a pedigree analysis has been made for polydactyly, the occurrence of extra fingers for three generations.

• It is customary in pedigree diagrams that square represent males and circles represent females.
• The shaded square or circles in the figure represents polydactyly condition, while unshaded one representing individuals with the usual fingers.
• Here, we have a marriage between a polydactylous man and a "normal" woman (generation I).
• They produce three children, a polydactylous daughter, a polydactylous son and a normal son (generation II).
• The first and third individuals of second generation, each marry "normal persons," their children are shown in third generation.
• From the analysis of pedigree of polydactyly, one fact becomes clear that a polydactylous offspring appears only when at least one parent is polydactylous.

 

Pedigree Analysis:

• This is a technique or a  chart which represents a family tree, that displays the members of the family who are affected by a genetic trait.