Question

Here is a portion of the nucleotide sequence in phenylalanine tRNA. $$ 3 ' \text { '-ACCACCUGCUCAGGCCUU- } 5^{\prime} $$ Write the nucleotide sequence of its DNA complement.

Short answer

Answer: The DNA complement of the given RNA sequence is 5' - TGGTGACGAGTCCGGAA - 3'.

Step-by-step solution

Replace uracil with thymine in the RNA sequence

To convert the RNA sequence to its DNA equivalent, replace all instances of uracil (U) with thymine (T): RNA sequence: 3' - ACCACCUGCUCAGGCCUU - 5' DNA equivalent: 3' - ACCACCTGCTCAGGCCTT - 5'

Find the complementary DNA sequence

Now that we have the DNA equivalent of the RNA sequence, we can find the complementary DNA sequence by pairing adenine (A) with thymine (T) and cytosine (C) with guanine (G). The complementary DNA sequence will have a 5' to 3' orientation: DNA sequence (3' to 5'): 5' - TGGTGACGAGTCCGGAA - 3' Complementary DNA sequence: 3' - ACCACCTGCTCAGGCCTT - 5' The DNA complement of the given RNA sequence is: $$ 5^{\prime} \text { -TGGTGACGAGTCCGGAA-} 3^{\prime} $$

Key concepts

Nucleotide Sequence

The nucleotide sequence is the order of nucleotides in a DNA or RNA strand. Each nucleotide consists of a sugar, a phosphate group, and a nitrogenous base. In DNA, these bases are adenine (A), cytosine (C), guanine (G), and thymine (T), while in RNA, uracil (U) replaces thymine.

Understanding the nucleotide sequence is essential for many biological processes, as the sequence determines the information carried by a DNA or RNA molecule, which in turn can dictate cell function, protein synthesis, and hereditary traits. When looking at the exercise provided, identifying the nucleotide sequence in the tRNA and converting it to its DNA complement involves understanding which nitrogenous bases are present and how they relate to the DNA structure.

Base Pairing Rules

Base pairing rules are fundamental to DNA structure and function. They state that in DNA, adenine (A) pairs with thymine (T) and cytosine (C) pairs with guanine (G), forming the characteristic double helix structure. In RNA, adenine pairs with uracil (U) instead of thymine.

Example of Base Pairing

For the given RNA sequence 3' - ACCACCUGCUCAGGCCUU - 5', we first replace uracil with thymine for DNA pairing. The resulting sequence is 3' - ACCACCTGCTCAGGCCTT - 5'. Following base pairing rules to find its complement: A pairs with T, and C pairs with G. Therefore, the complementary DNA sequence read in the 5' to 3' direction is 5' - TGGTGACGAGTCCGGAA - 3'.

Correctly applying the base pairing rules is vital for replicating the genetic information accurately, whether it is during DNA replication, transcription, or during laboratory exercises like the one shown.

Transcription Process

The transcription process is how genetic information from DNA is copied into RNA. During transcription, RNA polymerase binds to a DNA sequence at the promoter region and then unwinds the DNA. It then synthesizes a complementary RNA strand from one of the unwound DNA strands known as the template strand.

Transcription Steps

This process entails several steps including initiation, elongation, and termination. In the example we have, the RNA has already been synthesized from DNA, hence showing a sequence, which is complementary to the DNA template strand it was transcribed from. After transcription, the RNA molecule undergoes post-transcriptional modifications before it becomes fully functional for protein synthesis in translation. Teaching the transcription process helps students understand how genetic codes are expressed and regulated within the cell.