Question

Figures (a) to (d) given below represent the type of ear lobes present in a family consisting of 2 children - Rahul, Nisha and their parents.

(a) Rahul's Father	(b) Rahul	(c) Rahul's Mother	(d) Rahul's sister Nisha
(e)		(f)
Types of ear lobes

Excited by his observation of different types of ear lobes present in his family, Rahul conducted a survey of the type of ear lobes found {Figure (e) and (f)} in his classmates. He found two types of ear lobes in his classmates as per the frequency given below:

Sex	Free	Attached
Male	36	14
Female	31	19

On the basis of the above data answer the following questions.

1. Which of the two characteristics - ‘free ear lobe’ or ‘attached ear lobe’ appears to be dominant in this case? Why?
2. Is the inheritance of the free ear lobe linked with the sex of the individual? Give a reason for your answer.
3. What type of ear lobe is present in father, mother, Rahul and his sister Nisha? Write the genetic constitution of each of these family members which explains the inheritance of this character in this family.
   (Gene for the Free ear lobe is represented by F and the gene for the attached ear lobe is represented by f for writing the genetic constitution).
   OR
   Suresh’s parents have attached ear lobes. What type of ear lobe can be seen in Suresh and his sister Siya? Explain by giving the genetic composition of all.

Answer 1

1. The free ear lobe is dominant because it is found in a large majority of the population.
2. No. It is not sex-linked. As per the data of the family as well as the class, it is indicated that the free ear lobe is present in males as well as in females.
3. Father - Ff (free ear lobe), Mother - Ff (free ear lobe), Rahul - ff (attached ear lobe) and Nisha - Ff (free ear lobe)
   OR
   Suresh’s father - ff (attached ear lobe), mother - ff (attached ear lobe), Suresh - ff (attached ear lobe), Siya - ff (attached ear lobe). If both parents have recessive characters, then all the children can have recessive characters only.