Year-wise Biology practice

NEET 2019 Biology PYQs

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90 questions in this collection · Page 6 of 9

Question 51 of 90

🟢 NEET 2019 📘 CLASS XII

Principles Of Inheritance And Variation

What map unit (Centimorgan) is adopted in the construction of genetic maps?

AI-generated explanation. Check against your textbook.

Explanation:

In NCERT, one map unit is a centimorgan, which corresponds to a 1% recombination frequency between two genes on a chromosome. So, the distance between two genes is measured by the percentage of offspring showing recombination. A 1% recombination means a 1 cM distance. The correct option is 4: 1% cross over.

🧠 Did You Know?

Recombination frequency cannot exceed 50% for genes that are linked; 50% or more indicates genes behave as if on different chromosomes (independent assortment).

💡 NCERT Memory Line:

A centimorgan (cM) is the unit of map distance; 1 cM equals 1% recombination between two genes.

Question 52 of 90

🟢 NEET 2019 📘 CLASS XII

Principles Of Inheritance And Variation

The frequency of recombination between gene pairs on the same chromosome as a measure of the distance between genes was explained by:

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Question 53 of 90

🟢 NEET 2019 📘 CLASS XII

Principles Of Inheritance And Variation

Select the incorrect statement.

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Explanation:

Option 2 is incorrect. In domesticated birds (fowls), the sex of the offspring is determined by the egg (the female gamete), which can carry either Z or W. The sperm always carries only a Z chromosome. Thus, sex is determined by the type of egg, not the sperm, according to NCERT biology.

🧠 Did You Know?

In birds, females are the hens (ZW) and males are the cocks (ZZ). The egg determines whether the offspring will be male (ZZ) or female (ZW).

💡 NCERT Memory Line:

In birds, sex determination is by the egg and the W chromosome in eggs decides female offspring, while the sperm contributes only Z.

Question 54 of 90

🟢 NEET 2019 📘 CLASS XII

Principles Of Inheritance And Variation

Under which of the following conditions will there be no change in the reading frame of following mRNA?
5'AACAGCGGUGCUAUU3'

AI-generated explanation. Check against your textbook.

Explanation:

The reading frame is set by codons of three bases. The given mRNA has codons: AAC | AGC | GGU | GCU | AUU. Deleting an entire codon (GGU at positions 7–9) removes 3 bases, preserving the frame. Hence, no shift occurs with option 1.

🧠 Did You Know?

Inserting or deleting any number of bases not divisible by three shifts the reading frame (frameshift), changing all downstream codons and potentially altering the protein.

💡 NCERT Memory Line:

A reading frame is read in consecutive triplets; indels not in multiples of three cause frameshifts and alter the amino acid sequence.

Question 55 of 90

🟢 NEET 2019 📘 CLASS XII

Principles Of Inheritance And Variation

What is the genetic disorder in which an individual has an overall masculine development, gynaecomastia and is sterile?

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Question 56 of 90

🟢 NEET 2019 📘 CLASS XII

Molecular Basis Of Inheritance

Purines found both in DNA and RNA are:

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Question 57 of 90

🟢 NEET 2019 📘 CLASS XII

Molecular Basis Of Inheritance

Which of the following features of genetic code does allow bacteria to produce human insulin by recombinant DNA technology?

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Question 58 of 90

🟢 NEET 2019 📘 CLASS XII

Molecular Basis Of Inheritance

Expressed Sequence Tages (ESTs) refers to:

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Question 59 of 90

🟢 NEET 2019 📘 CLASS XII

Molecular Basis Of Inheritance

Match the following genes of the Lac operon with their respective products.

(A)i gene	(I)β-galactosidase
(B)z gene	(II)Permease
(C)a gene	(III)Repressor
(D)y gene	(IV)Transacetylase

Select the correct option.

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Question 60 of 90

🟢 NEET 2019 📘 CLASS XII

Evolution

Variations caused by mutation, as proposed by Hugo de Vries, are:

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