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Molecular Basis of Inheritance · Question 97

NEET 2013MCQMedium📈 Topic in 88% papers+4−1
1

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

Answer

(4) -galactosidase

Solution

The lac operon has three structural genes in the order z y a, transcribed as one polycistronic mRNA:

z codes for -galactosidase, y codes for permease and a codes for transacetylase.

⇒ A non-sense mutation in the y gene creates a premature stop codon, so a complete, functional permease is not formed.

∵ Translation of the downstream a gene is also stopped (polar effect), transacetylase is not formed either.

∴ Only -galactosidase, coded by the upstream z gene, is produced.

Answer: (4)

NEET 2013

Keep practising — Molecular Basis of Inheritance

2

[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)
3

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

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

In an inducible operon, the genes are :

  1. usually expressed unless a signal turns them "off"
  2. always expressed
  3. never expressed
  4. usually not expressed unless a signal turns them "on"
NEET 2013 (Karnataka)
5

One of the most frequently used techniques in DNA fingerprinting is :-

  1. SSCP
  2. SCAR
  3. VNTR
  4. AFLP
NEET 2013 (Karnataka)
6

Read the following four statements (A-D) : How many of the above statements are right ?

  1. Four
  2. Two
  3. Three
  4. One
AIPMT 2012 (Mains)
7

What is it that forms the basis of DNA Fingerprinting ?

  1. The relative proportions of purines and pyrimidines in DNA
  2. The relative amount of DNA in the ridges and grooves of the fingerprints
  3. The relative difference in the DNA occurrence in blood, skin and saliva
  4. Satellite DNA occurring as highly repeated short DNA segments
AIPMT 2012 (Mains)
8

Removal of introns and joining of exons in a defined order during transcription is called

  1. Looping
  2. Inducing
  3. Slicing
  4. Splicing
AIPMT 2012 (Prelims)
9

If one strand of DNA has the nitrogenous base sequence as ATCTG, what would be the complementary RNA strand sequence

  1. ATCGU
  2. UAGAC
  3. AACTG
  4. TTAGU
AIPMT 2012 (Prelims)
10

Which one of the following is not a part of a transcription unit in DNA ?

  1. The structural gene
  2. The inducer
  3. A terminator
  4. A promoter
AIPMT 2012 (Prelims)
11

Removal of RNA polymerase-III from nucleoplasm will affect the synthesis of

  1. tRNA
  2. hnRNA
  3. rRNA
  4. mRNA
AIPMT 2012 (Prelims)

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