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Molecular Basis of Inheritance · Question 89

AIPMT 2015 (Cancelled)MCQEasy📈 Topic in 88% papers+4−1
1

Gene regulation governing lactose operon of E. coli that involves the lac I gene product is

  1. negative and inducible because repressor protein prevents transcription.
  2. positive and inducible because it can be induced by lactose
  3. negative and repressible because repressor protein prevents transcription
  4. feedback inhibition because excess of -galactosidase can switch off transcription

Answer

(1) negative and inducible because repressor protein prevents transcription.

Solution

As per NCERT, the i gene of the lac operon codes for the repressor protein.

∵ In the absence of an inducer, the repressor binds to the operator and prevents RNA polymerase from transcribing the operon.

⇒ The control is exercised by a repressor, so the regulation of lac operon by repressor is referred to as negative regulation.

∵ Lactose (or allolactose) acts as an inducer: it binds the repressor, inactivates it and switches the operon on.

∴ The lac operon is negative and inducible because the repressor protein prevents transcription.

Answer: (1)

AIPMT 2015 (Cancelled)

Keep practising — Molecular Basis of Inheritance

2

In sea urchin DNA, which is double stranded, 17% of the bases were shown to be cytosine. The percentages of the other three bases expected to be present in this DNA are

  1. G 17%, A 16.5%, T 32.5%
  2. G 17%, A 33%, T 33%
  3. G 8.5%, A 50%, T 24.5%
  4. G 34%, A 24.5%, T 24.5%
AIPMT 2015 (Cancelled)
3

Which one of the following is wrongly matched?

  1. Transcription – Writing information from DNA to t-RNA
  2. Operon – Structural genes, operator and promoter
  3. Repressor protein – Binds to operator to stop enzyme synthesis
  4. Translation – Using information in m-RNA to make protein.
AIPMT 2014
4

Transformation was discovered by :

  1. Griffith
  2. Watson and Crick
  3. Hershey and Chase
  4. Meselson and Stahl
AIPMT 2014
5

Select the correct option ;

  1. Direction of RNA synthesis 3'–5', Direction of reading of the template DNA strand 5'–3'
  2. Direction of RNA synthesis 5'–3', Direction of reading of the template DNA strand 5'–3'
  3. Direction of RNA synthesis 5'–3', Direction of reading of the template DNA strand 3'–5'
  4. Direction of RNA synthesis 3'–5', Direction of reading of the template DNA strand 3'–5'
AIPMT 2014
6

An analysis of chromosomal DNA using the Southern hybridization technique does not use:

  1. Blotting
  2. PCR
  3. Electrophoresis
  4. Autoradiography
AIPMT 2014
7

Commonly used vectors for human genome sequencing are :

  1. BAC and YAC
  2. T/A Cloning Vectors
  3. T-DNA
  4. Expression Vectors
AIPMT 2014
8

The diagram shows an important concept in the genetic implication of DNA. Fill in the blanks A to C. [figure]

  1. A-translation B-extension C-Rosalind Franklin
  2. A-translation B-transcription C-Erwin Chargaff
  3. A-transcription B-translation C-Francis Crick
  4. A-transcription B-replication C-James Watson
NEET 2013
9

Which enzyme will be produced in a cell in which there is a non-sense mutation in the lac Y gene ?

  1. Transacetylase
  2. Lactose permease and transacetylase
  3. Lactose permease
  4. -galactosidase
NEET 2013
10

[figure] The figure gives an important concept in the genetic implication of DNA. Fill the blanks A, B and C.

  1. A - Erwin Chargaff B - translation C - replication
  2. A - Maurice Wilkins B - transcription C - translation
  3. A - Francis Crick B - translation C - transcription
  4. A - James Watson B - replication C - extension
NEET 2013 (Karnataka)
11

Which of the following is not a property of the genetic code ?

  1. Ambiguous
  2. Universal
  3. Degeneracy
  4. Non-overlapping
NEET 2013 (Karnataka)

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