C
CraftExam
medium difficulty6 min

Gene

A gene is a small functional part of DNA on a chromosome that carries information for a trait.

In one line: Gene means one instruction piece inside DNA.

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Understand it

A gene acts like an instruction unit inside the hereditary material. It does not work alone as a whole chromosome; instead, it is one useful section that helps decide a specific feature such as seed shape, flower colour, or height pattern. Different genes influence different traits, which is why parents pass information to children in an organised way.

Example

In pea plants, one gene can control stem height, while another gene can control seed shape. In humans, genes help decide features such as blood group and eye colour pattern.

Rule to remember

A gene is a segment of DNA on a chromosome; many genes together make up a chromosome.

See it worked out

Follow the example line by line, then use the same method on new questions.

Worked example

  1. 1If a pea plant has one gene for tallness and another for seed shape, each gene influences a different feature.
  2. 2The height gene helps decide whether the plant grows tall or short, while another gene decides a different trait.

Method you can reuse

  1. 1Identify the trait mentioned.
  2. 2Recall that the trait is controlled by genetic information.
  3. 3State that a gene is a segment of DNA on a chromosome.
  4. 4Add that different genes control different traits.
  5. 5Give one plant or human example.

Check yourself

Answer the question in your head before opening the answer.

Try it yourself

What does a gene do in heredity?

Think first, then show answer
A gene carries the information for a trait and passes that information from parents to offspring. It is a small functional part of DNA on a chromosome, so it acts as the basic unit of inheritance.

Common wrong answer

A common wrong answer is to call the gene the whole chromosome. The chromosome is bigger and carries many genes.

Don't mix this up

Students often say gene and chromosome are the same. That is wrong because a chromosome contains many genes, not just one.

Exam tip

When writing an answer, say gene is a unit of inheritance and mention that it is located on a chromosome.

Write it in the exam

Each point is worth about one mark. Write point 1 for a 1-mark question and keep adding points as the marks go up.

How CBSE asks it

Define a gene, state its location, or explain why genes are called units of heredity.
  1. 1

    Enough for 1 mark

    A gene is a small functional part of DNA on a chromosome that carries information for a trait.

  2. 2

    Add for 2 marks

    Example: In pea plants, one gene can control stem height, while another gene can control seed shape. In humans, genes help decide features such as blood group and eye colour pattern.

  3. 3

    Add for 3 marks

    A gene acts like an instruction unit inside the hereditary material.

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