Molecular Basis of Inheritance for NEET UG
How does DNA store information, copy itself and turn into proteins? This chapter covers DNA structure, replication, transcription, the genetic code, translation and gene regulation.
BiologyClass 1297 MCQs3 lessons15 flashcards2 memory tricks
Practise Molecular Basis of Inheritance free
What you'll learn
- DNA structure and replication
Describe the double helix and explain semi-conservative replication. - Transcription, the genetic code and translation
Explain how DNA is transcribed into RNA and translated into protein. - Gene regulation: the lac operon
Explain how the lac operon switches genes on and off.
Memory tricks
Purines: Adenine, Guanine. Pyrimidines: Cytosine, Uracil, Thymine.
G≡C pairs have 3 hydrogen bonds and A=T pairs have 2, so GC-rich DNA melts at a higher temperature. Chargaff: A = T, G = C.
Try 3 NEET-style questions
Q1. In the Hershey–Chase experiment, the radioactivity found inside the bacterial cells after blending and centrifugation came from
- ³⁵S-labelled protein
- ¹⁵N-labelled DNA
- ¹⁴C-labelled sugar
- ³²P-labelled DNA
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Answer: (4) ³²P-labelled DNA
Phages with ³²P-labelled DNA gave radioactive bacteria, while ³⁵S-labelled protein stayed in the supernatant. This showed that DNA, not protein, enters the bacterium as genetic material.
Q2. In DNA fingerprinting, the probe used to detect VNTR bands is
- a labelled single-stranded DNA that hybridises to the VNTR sequence
- an antibody against DNA
- a restriction enzyme
- a fluorescent protein
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Answer: (1) a labelled single-stranded DNA that hybridises to the VNTR sequence
A labelled VNTR probe (radioactive or fluorescent single-stranded DNA) hybridises with complementary sequences, and the bands are seen by autoradiography.
Q3. The idea that RNA was the first genetic material is supported by the fact that
- RNA is more stable than DNA
- RNA is always double-stranded
- RNA can act both as genetic material and as a catalyst
- RNA contains thymine
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Answer: (3) RNA can act both as genetic material and as a catalyst
Essential life processes evolved around RNA, which can store information and act as a catalyst (ribozymes). DNA evolved later as a more stable store.
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