The significance of nitrogenous bases in DNA primarily lies in the sequence and order of these bases, which ultimately determines the genetic code and the synthesis of proteins. Here's a breakdown of the statements you've provided, focusing on the significance of nitrogenous bases:
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The type of hydrogen bonding between the nitrogenous bases determines which amino acid will be added to the peptide chain.
- This statement is somewhat misleading. Hydrogen bonding occurs between specific pairs of nitrogenous bases (adenine with thymine, and cytosine with guanine) to stabilize the DNA structure. The actual determination of which amino acid is added to a peptide chain is linked to the codons in mRNA, which are transcribed based on the DNA sequence. The bonds themselves do not dictate amino acid addition.
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The number of adenines and cytosines determines the type of RNA that will be produced.
- This statement is inaccurate. While the presence of adenines and cytosines (and the other bases: thymine and guanine) does influence the RNA sequence transcribed from DNA, it's the specific sequence or order of all nitrogenous bases that determines the type of RNA produced (mRNA, rRNA, tRNA, etc.) and the proteins synthesized.
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The order of nitrogenous bases determines the order of amino acids in the proteins synthesized.
- This statement is correct. The sequence of nitrogenous bases in a gene specifies the sequence of codons in mRNA, which in turn determines the order of amino acids in the synthesized protein. This relationship is fundamental to the flow of genetic information (DNA → RNA → Protein).
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The amount of thymine and guanine in the DNA molecules determines the length of the genes.
- This statement is not accurate. The length of genes is determined by the overall sequence of nitrogenous bases (including all four bases: adenine, thymine, cytosine, and guanine). The proportions of individual bases do not directly correlate with gene length; rather, it’s the total number of base pairs that defines how long a gene is.
In summary, the most significant role of nitrogenous bases is their specific sequence, which encodes genetic information and dictates the synthesis of proteins through the genetic code.