Examkin

Soru

Zorluk: OrtaGene Mutations and Chromosomal Aberrations

Which of the following mutagenic agents primarily induces gene mutations by causing adjacent thymine bases on a single DNA strand to covalently bond and form pyrimidine dimers?

  1. Ultraviolet radiationCevap
  2. B
    Colchicine chemical solution
  3. C
    Ionizing X-ray radiation
  4. D
    Nitrous acid chemical mutagen

Cevap

Ultraviolet radiation is the mutagenic agent that causes adjacent thymine bases on a DNA strand to form pyrimidine dimers.
Ultraviolet radiation is absorbed strongly by pyrimidines, promoting covalent linkage between adjacent thymine bases on the same DNA strand. This forms thymine dimers that block normal DNA replication and transcription.

Adım Adım Çözüm

1
Identify the primary mechanism of action described in the stem.
The mechanism is the formation of intrastrand thymine (pyrimidine) dimers due to absorption of radiant energy.
Different physical and chemical mutagens operate through distinct biochemical pathways on nucleic acids.
2
Evaluate physical versus chemical mutagens.
Non-ionizing ultraviolet (UV) light specifically excites pyrimidine rings (thymine and cytosine), leading to covalent dimer formation.
UV light lacks the energy to ionize atoms or break double strands, but has sufficient energy to alter nitrogenous base bonding.

Anahtar Kavram

Physical mutagens and the molecular mechanism of UV-induced pyrimidine dimerization
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Konular

Gene Mutations and Chromosomal Aberrations

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