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Molecular Basis of Inheritance · Question 123

AIPMT 2008MCQEasy📈 Topic in 75% papers+4−1
1

In the DNA molecule:

  1. the total amount of purine nucleotides and pyrimidine nucleotides is not always equal
  2. there are two strands which run antiparallel one in 5' 3' direction and other in 3' 5'
  3. there are two strands which run parallel in the 5' 3' direction
  4. the proportion of adenine in relation to thymine varies with the organism

Answer

(2) there are two strands which run antiparallel one in 5' 3' direction and other in 3' 5'

Solution

As per NCERT, the two polynucleotide chains of DNA have anti-parallel polarity: if one chain has the polarity 5' 3', the other has 3' 5'.

∵ A pairs with T and G pairs with C (Chargaff's rule) ⇒ purines = pyrimidines always, and A : T = 1 in every organism.

∴ Only the statement about antiparallel strands is correct.

Answer: (2)

AIPMT 2008

Keep practising — Molecular Basis of Inheritance

2

Which one of the following pairs of nitrogenous bases of nucleic acids is wrongly matched with the category mentioned against it?

  1. Thymine, Uracil — Pyrimidines
  2. Guanine, Adenine — Purines
  3. Uracil, Cytosine — Pyrimidines
  4. Adenine, Thymine — Purines
AIPMT 2008
3

Which one of the following pairs of codons is correctly matched with their function or the signal for the particular amino acid?

  1. UUA, UCA — Leucine
  2. AUG, ACG — Start/Methionine
  3. UAG, UGA — Stop
  4. GUU, GCU — Alanine
AIPMT 2008
4

One turn of the helix in a B-form DNA is approximately -

  1. 20 nm
  2. 3.4 nm
  3. 2 nm
  4. 0.34 nm
AIPMT 2006
5

One gene-one enzyme hypothesis was postulated by -

  1. A. Garrod
  2. Hershey and Chase
  3. Beadle and Tatum
  4. R. Franklin
AIPMT 2006
6

Antiparallel strands of a DNA molecule means that-

  1. The phosphate groups at the start of two DNA strands are in opposite position (pole)
  2. One strand turns anti-clockwise
  3. One strand turns clockwise
  4. The phosphate groups of two DNA strands, at their ends, share the same position
AIPMT 2006
7

Which antibiotic inhibits interaction between tRNA and mRNA during bacterial protein synthesis?

  1. Neomycin
  2. Erythromycin
  3. Tetracycline
  4. Streptomycin
AIPMT 2006
8

Amino acid sequence, in protein synthesis is decided by the sequence of -

  1. cDNA
  2. mRNA
  3. tRNA
  4. rRNA
AIPMT 2006
9

E. coli cells with a mutated z gene of the lac operon cannot grow in medium containing only lactose as the source of energy because -

  1. They cannot transport lactose from the medium into the cell
  2. They cannot synthesize functional -galactosidase
  3. In the presence of glucose, E. coli cells do not utilize lactose
  4. The lac operon is constitutively active in these cells
AIPMT 2005
10

Telomerase is an enzyme which is a -

  1. RNA
  2. Repetitive DNA
  3. Simple protein
  4. Ribonucleoprotein
AIPMT 2005
11

Protein synthesis in an animal cell occurs -

  1. On ribosomes present in the nucleolus as well as in cytoplasm
  2. On ribosomes present in cytoplasm as well as in mitochondria
  3. Only on the ribosomes present in cytosol
  4. Only on ribosomes attached to the nuclear envelope and endoplasmic reticulum
AIPMT 2005

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