Question

The symbols of empty circles used in pedigree represents
A. Normal Female
B. Normal males
C. Affected females
D. Affected males

Answer 1

Hint: Pedigree is the record of genetic traits for generations that are represented in the form of family trees. In pedigree, the affected individuals are represented by the filled symbols.

Complete answer:
Archibald Garrod firstly studied human genetics, he studied black urine disease alkaptonuria and stated that it is inherited by recessive genes. Archibald Garrod is the “Father of human genetics”.
In human, the study of inheritance is very difficult because:
> Cross cannot be controlled.
> Sexual maturity achieved after 15 years and life span is very long.
> In later stages of life, many phenotypes are visible.
> The offsprings produced in very small numbers.
So, to overcome these difficulties Francis Galton (Father of Eugenics) gave pedigree analysis.
Pedigree analysis is the record and analysis of inheritance of a particular trait throughout the family with the help of diagrams. The most common pedigree analysis is the pedigree of Haemophilia in the descendants of Queen Victoria.
> Square represents the male and a circle represents the female.
> Horizontal lines represent the parents and vertical lines are for their offspring.
> The filled symbol shows that, if an individual is known to have symptoms of disease.
> Sometimes the half-filled symbol indicates a known to be a carrier of disease, therefore this is for someone who does not have the symptom of disease but can pass the symptoms to the generations as a heterozygote.
> The siblings are the offsprings of a parent.
> Pedigree analysis is the study of pedigree for the transmission of a particular trait in a homozygous or heterozygous state in an individual.

Note: Pedigree analysis is useful in determining the genetic disorders like alkaptonuria, color blindness, phenylketonuria, sickle cell anaemia and haemophilia etc.
Pedigree analysis applied two tools:
> It realized the probability ratio in the progeny.
> It eliminates the alternatives.