Question

An RNA molecule was synthesized to complementary base pair with a DNA molecule. The sequence of the DNA was: 5' ATCCGCTAAG 3'. The RNA sequence should be: A. 5' CUUAGCGGAU 3' B. 5' UAGGCGAUUC 3' C. 5' CTTAGCGGAT 3' D. 5' TAGGCGATTC 3'

Short answer

The correct RNA sequence is option B. 5' UAGGCGAUUC 3'.

Step-by-step solution

Understanding Base Pairing Rules

Understand that in DNA, adenine (A) pairs with thymine (T) and cytosine (C) pairs with guanine (G). In RNA, adenine (A) pairs with uracil (U) instead of thymine (T). Review the base pairing rules to be able to determine the complementary RNA sequence.

Transcribing DNA to RNA

Write down the complementary RNA base for each DNA base in the given sequence, keeping in mind the base pairing rules from Step 1. Make sure to follow the same 5' to 3' direction as the DNA sequence.

Comparing with Given Options

Compare the RNA sequence obtained from Step 2 with the given answer choices to find the correct RNA sequence.

Key concepts

Base Pairing Rules

When it comes to understanding genetics, a fundamental concept is how nucleotides pair together. This rule is crucial for the replication of DNA and the transcription of RNA. In DNA, the bases pair as adenine (A) with thymine (T), and cytosine (C) with guanine (G). However, during RNA transcription, the rule changes slightly because RNA contains uracil (U) instead of thymine. So, adenine (A) then pairs with uracil (U) in RNA.

In a simple way, you can think of it as A pairing with U (instead of T as in DNA), and C still pairing with G when converting DNA into RNA. This is a strict rule and does not change, ensuring the genetic code is accurately passed on during the process of transcription, where an RNA sequence is produced to mirror the DNA template.

DNA to RNA

The process of turning a DNA sequence into its RNA counterpart is known as transcription. This is akin to translating one language to another while preserving the original message. Given a DNA strand, transcription takes place in a step where an enzyme called RNA polymerase reads the original DNA sequence and synthesizes a complementary RNA strand.

Let's apply the base pairing rules to the DNA sequence '5' ATCCGCTAAG 3''. The transcript produced would start with a 'U' (replacing 'A'), followed by 'A' (complementary to 'T'), and continue adhering to this pattern. Every 'A' in DNA becomes a 'U' in RNA, 'T' becomes 'A', 'C' stays with 'G', and 'G' stays with 'C'. The result should be an RNA strand that starts at the 5' end and continues to the 3' end, just like the DNA strand, but with the adjusted base pairs according to RNA rules.

Nucleic Acid Complementarity

Nucleic acid complementarity refers to the specific pairing between nucleobases that allows the double helix structure of DNA to maintain its uniform shape and the RNA molecule to accurately carry the genetic message from DNA. This complementarity is based on the ability of bases to form hydrogen bonds with their correct partners: A with T (or U in RNA) and C with G.

In the exercise, you're asked to apply these complementary base pairing rules to derive an RNA sequence that would effectively pair with a given DNA sequence. This concept is essential because it ensures that genetic information is consistently and accurately conveyed from DNA to RNA, and then to proteins in a process known as gene expression. It's the foundation of heredity, the genetic blueprint that dictates an organism's characteristics.