Year-wise Biology practice

NEET (Sept)2020 Biology PYQs

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90 questions in this collection · Page 6 of 9

Question 51 of 90
🟢 NEET (Sept)2020 📘 CLASS XII

Human Reproduction

Meiotic division of the secondary oocyte is completed:

AI-generated explanation. Check against your textbook.

Explanation:

The secondary oocyte is arrested in metaphase II and completes meiosis II only after fertilization. When a sperm fuses with the ovum, the oocyte finishes meiosis II, forming the mature ovum and a second polar body. Hence, the meiotic division is completed at the time of fusion of a sperm with an ovum (option 4).

🧠 Did You Know?

Fertilization triggers the last meiotic division, ensuring the haploid number is restored in the zygote.

💡 NCERT Memory Line:

The secondary oocyte completes meiosis II only upon fertilization, forming the mature ovum.

Question 52 of 90
🟢 NEET (Sept)2020 📘 CLASS XII

Reproductive Health

Select the option including all sexually transmitted diseases.
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Question 53 of 90
🟢 NEET (Sept)2020 📘 CLASS XII

Reproductive Health

In which of the following techniques, the embryos are transferred to assist those females who cannot conceive?
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Question 54 of 90
🟢 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?
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Question 55 of 90
🟢 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.

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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 56 of 90
🟢 NEET (Sept)2020 📘 CLASS XII

Principles Of Inheritance And Variation

Experimental verification of the chromosomal theory of inheritance was done by:
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Question 57 of 90
🟢 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 58 of 90
🟢 NEET (Sept)2020 📘 CLASS XII

Molecular Basis Of Inheritance

Name the enzyme that facilitates opening of DNA helix during transcription.
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Question 59 of 90
🟢 NEET (Sept)2020 📘 CLASS XII

Molecular Basis Of Inheritance

Which of the following statements is correct?
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Question 60 of 90
🟢 NEET (Sept)2020 📘 CLASS XII

Molecular Basis Of Inheritance

If the distance between two consecutive base pairs is 0.34 nm and the total number of base pairs of a DNA double helix in a typical mammalian cell is 6.6×109 bp, then the length of the DNA is approximately:
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