Class XII · Biology practice

Principles of Inheritance and Variation PYQs

Check your understanding, bookmark questions and revisit your mistakes.

Page score: 0/40
Choose an answer to begin.

Practice scoring: +4 correct, 0 incorrect. Filters apply to this page. Use timed tests for negative marking.

Answers and bookmarks are saved in this browser, across visits. They do not sync to your account.

39 questions in this collection · Page 2 of 4

Question 11 of 39
🟢 NEET 2021 📘 CLASS XII

Principles Of Inheritance And Variation

The production of gametes by the parents, formation of zygotes, the F1 and F2 plants, can be understood from a diagram called:
Request an AI explanation using Show explanation.
Question 12 of 39
🟢 NEET 2021 📘 CLASS XII

Principles Of Inheritance And Variation

In a cross between a male and female, both heterozygous for sickle cell anaemia gene, what percentage of the progeny will be diseased?
Request an AI explanation using Show explanation.
Question 13 of 39
🟢 NEET (Sept)2020 📘 CLASS XII

Principles Of Inheritance And Variation

How many true breeding pea plant varieties did Mendel select as pairs, which were similar except in one character with contrasting traits?
Request an AI explanation using Show explanation.
Question 14 of 39
🟢 NEET (Sept)2020 📘 CLASS XII

Principles Of Inheritance And Variation

Identify the wrong statement with reference to the gene 'I' that controls ABO blood groups.

AI-generated explanation. Check against your textbook.

Explanation:

The wrong statement is option 3. In the ABO system, IA and IB are codominant; when both are present (IAIB), the person has AB blood type with both A and B antigens. The statement says they express the same sugar, which is incorrect because A and B antigens are different sugars on RBC surfaces.

🧠 Did You Know?

Allele i is recessive and does not code for A or B antigens; individuals with ii blood type have no A or B antigens (O blood group).

💡 NCERT Memory Line:

The gene I has three alleles (IA, IB, i); a person carries two alleles, and IA and IB show codominance to yield AB type when present together.

Question 15 of 39
🟢 NEET (Sept)2020 📘 CLASS XII

Principles Of Inheritance And Variation

Experimental verification of the chromosomal theory of inheritance was done by:
Request an AI explanation using Show explanation.
Question 16 of 39
🟢 NEET (Sept)2020 📘 CLASS XII

Principles Of Inheritance And Variation

Select the correct match.

AI-generated explanation. Check against your textbook.

Explanation:

Option 3 is correct. Sickle cell anaemia is an autosomal recessive disorder caused by a mutation in the beta-globin gene on chromosome 11. Children must inherit two faulty copies to express the disease. Options 1, 2 and 4 are incorrect according to NCERT: haemophilia is X-linked recessive (not Y-linked); phenylketonuria is autosomal recessive (not dominant); thalassemia is also autosomal recessive (not X-linked).

🧠 Did You Know?

Carriers (heterozygotes) for sickle cell trait usually do not show full disease but may have some abnormal Hb; this trait is more common in populations where malaria is or was prevalent.

💡 NCERT Memory Line:

“Sickle cell anaemia is an autosomal recessive disorder due to mutation in beta-globin gene on chromosome 11.”

Question 17 of 39
🟢 NEET (Oct)2020 📘 CLASS XII

Principles Of Inheritance And Variation

The number of contrasting characters studied by Mendel for his experiments was:
Request an AI explanation using Show explanation.
Question 18 of 39
🟢 NEET (Oct)2020 📘 CLASS XII

Principles Of Inheritance And Variation

Chromosomal theory of inheritance was proposed by:
Request an AI explanation using Show explanation.
Question 19 of 39
🟢 NEET (Oct)2020 📘 CLASS XII

Principles Of Inheritance And Variation

The best example for pleiotropy is:

AI-generated explanation. Check against your textbook.

Explanation:

The best example of pleiotropy is Phenylketonuria (PKU). In pleiotropy, a single gene affects many traits. The PKU gene causes a deficiency of the enzyme phenylalanine hydroxylase, leading to accumulation of phenylalanine and affecting multiple body processes. This results in various problems such as intellectual disability, growth issues, and other metabolic effects, illustrating one gene influencing several traits.

🧠 Did You Know?

NCERT discusses pleiotropy with examples like PKU to show how a single gene mutation can impact more than one phenotype.

💡 NCERT Memory Line:

Pleiotropy: one gene, many effects.

Question 20 of 39
🟢 NEET 2019 📘 CLASS XII

Principles Of Inheritance And Variation

In Antirrhinum (Snapdragon), a red flower was crossed with a white flower and in F1 generation, pink flowers were obtained. When pink flowers were selfed, the F2 generation showed white, red and pink flowers.
Choose the incorrect statement from the following :

AI-generated explanation. Check against your textbook.

Explanation:

The cross red x white in Antirrhinum shows incomplete dominance, yielding pink in F1. In F2, segregation of alleles gives 1 red : 2 pink : 1 white, confirming incomplete dominance and that the Law of Segregation does apply (gametes carry alleles, and they segregate during formation). Therefore statement 1 is incorrect. Statements 2, 3, and 4 are consistent with NCERT: ratio 1/4 red, 1/2 pink, 1/4 white; pink in F1 results from incomplete dominance; and the experiment does not follow complete dominance.

🧠 Did You Know?

In incomplete dominance, heterozygotes show a third phenotype (pink) distinct from either homozygote (red or white).

💡 NCERT Memory Line:

Antirrhinum shows incomplete dominance; F2 phenotype ratio is 1:2:1 (red:pink:white) due to segregation of alleles.

Page score: 0/40