MCQ Detailed View

Proteins are made up of smaller building blocks called amino acids, and each amino acid is coded by a specific sequence of three nucleotide bases (triplet) in the DNA. This triplet, also called a codon, tells the cell which amino acid should be added to a growing protein chain during protein synthesis.Valine is one of the 20 standard amino acids. The DNA codons that code for valine are derived from the complementary codons in messenger RNA (mRNA). In the genetic code, the mRNA codons for valine are GUU, GUC, GUA, and GUG. Since DNA uses thymine (T) instead of uracil (U), the corresponding DNA triplets for valine are:

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  CAA (for GUU)

  
  


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  CAC (for GUG)

  
  


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  CAG (for GUC)

  
  


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  CAT (for GUA)

  
  

However, among the given options, only CAT appears similar but actually codes for the amino acid histidine in most contexts. The exact standard codons for valine in DNA are GTT, GTC, GTA, and GTG. None of the options given match these correct codons.

Let's analyze the provided options:

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  CTT: Codes for leucine, not valine.

  
  


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  AGU: This is an RNA codon (not DNA) for serine.

  
  


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  CAT: Codes for histidine.

  
  


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  AAT: Codes for asparagine.

  
  

Thus, none of these options accurately represent the DNA codon for valine, making Option 5: None of these the correct answer.

Understanding codons and their corresponding amino acids is a fundamental part of molecular biology and genetics. The genetic code is universal for almost all living organisms, meaning that the same codons specify the same amino acids in different species. This principle forms the basis of how DNA information is translated into proteins, which are vital for all life processes