Case Study:

Rohan, a Class 10 student from Delhi, recently noticed that many members of his family share similar physical traits. His father and grandfather both have free earlobes, while his mother has attached earlobes. Rohan also has free earlobes like his father. This made him curious about how such family traits are inherited.

During his biology class on heredity and evolution, Rohan learned that traits are passed from parents to offspring through genes, which are units of heredity. These genes are inherited from both parents and determine many physical characteristics such as hair type, eye colour, blood group, and ear lobe structure. 

Scientists discovered the basic rules of inheritance through the experiments of Gregor Mendel, who studied pea plants and showed that some traits are dominant, while others are recessive. Dominant traits appear in the offspring even if only one parent contributes the gene, while recessive traits appear only when both parents pass the same gene.

For example, if the gene for free earlobes (F) is dominant and the gene for attached earlobes (f) is recessive, a child receiving genes Ff will show free earlobes. However, only individuals with ff genotype will have attached earlobes.

Rohan’s teacher explained that each child receives one gene from the mother and one gene from the father, which is why siblings may share similarities but are not identical in all traits. 

In Rohan’s family, his father might have the genotype Ff, while his mother could be ff. This explains why Rohan inherited free earlobes while his mother has attached earlobes.

This simple family example demonstrates how heredity works and how genetic traits are passed across generations, forming the basis of genetics and the study of evolution.

Questions

Section A – MCQs

1. Rohan has free earlobes while his mother has attached earlobes. This difference occurs due to:

A. Environmental factors only
B. Inheritance of genes from parents
C. Eating habits
D. Climate conditions

2. If free earlobes (F) are dominant and attached earlobes (f) are recessive, which genotype will show attached earlobes?

A. FF
B. Ff
C. ff
D. FFF

3. A child receives genetic information from:

A. Father only
B. Mother only
C. Both parents
D. Grandparents only

4. In genetics, a trait that appears even when only one copy of the gene is present is called:

A. Recessive trait
B. Dominant trait
C. Mutated trait
D. Acquired trait

Section B - Short Answer Questions

1. What is heredity? Explain using an example from a family.

2. Differentiate between dominant and recessive traits with one example.

3. Why do siblings from the same parents often show different traits?

Section C - Long Answer Question

1. A family shows variation in hair type. The father has curly hair (dominant trait), while the mother has straight hair (recessive trait).

Analyze the situation and answer the following:

• Explain how the child may inherit curly or straight hair.
• Show the possible genetic combinations using symbols.
• Why might two siblings have different hair types?

Answer Key

MCQ Answers

1. B - Inheritance of genes from parents
2. C - ff
3. C - Both parents
4. B - Dominant trait

Short Answer Solutions

1. Heredity is the transmission of traits from parents to offspring through genes. For example, a child may inherit eye colour or earlobe type from parents.

2. Dominant traits appear even if only one copy of the gene is present (e.g., free earlobes).
    Recessive traits appear only when both gene copies are recessive (e.g., attached earlobes).

3. Siblings receive different combinations of genes from their parents. Therefore, even though they share the same parents, they may inherit different traits.

Long Answer Solution

If curly hair (C) is dominant and straight hair (c) is recessive:

Possible parental genotypes:
Father --> Cc
Mother --> cc

Possible combinations for children:

Thus, some children may have curly hair (Cc) while others may have straight hair (cc).

Two siblings may have different hair types because they inherit different gene combinations from their parents.