Descriptions a–f refer to different types of RNA. Which classification correctly matches each description with tRNA, mRNA or rRNA? a) contains an anticodon b) specifies the amino acid sequence of a protein c) contains exons d) has amino acids covalently attached e) is a component of ribosomes f) is the most abundant form of RNA in the cell

Introduction / Context:
Cells use three main types of RNA to express genetic information: messenger RNA (mRNA), transfer RNA (tRNA) and ribosomal RNA (rRNA). Each type has distinct structural features and specific roles in protein synthesis. This question gives a series of descriptions labelled a to f and asks you to correctly assign them to tRNA, mRNA or rRNA. It tests your detailed understanding of RNA structure and function in the central dogma of molecular biology.

Given Data / Assumptions:

Description a: contains an anticodon. Description b: specifies the amino acid sequence for a protein. Description c: contains exons. Description d: has amino acids covalently attached. Description e: is a component of ribosomes. Description f: is the most abundant form of RNA. We must match each description with tRNA, mRNA or rRNA and select the option that does so correctly.

Concept / Approach:
tRNA molecules carry amino acids to the ribosome and possess an anticodon loop that base pairs with codons on mRNA. Each tRNA can be charged with a specific amino acid, forming a covalent bond between the amino acid and the tRNA's 3' end. Therefore, descriptions a (contains an anticodon) and d (has amino acids covalently attached) clearly refer to tRNA. mRNA is the transcript copy of a gene that carries the coded information for the amino acid sequence of a protein; after processing in eukaryotes, it contains only exons. Thus, b (specifies amino acid sequence) and c (contains exons) describe mRNA. rRNA is a structural and functional component of ribosomes and is the most abundant RNA in cells, matching e and f.

Step-by-Step Solution:
Step 1: For description a (contains an anticodon), recall that only tRNA has an anticodon loop to recognise mRNA codons. Step 2: For description d (has amino acids covalently attached), remember that aminoacyl tRNA synthetases attach specific amino acids to tRNA, so this also points to tRNA. Step 3: For description b (specifies the amino acid sequence of a protein), recognise that mRNA carries the codon sequence that determines the order of amino acids, so this describes mRNA. Step 4: For description c (contains exons), understand that in eukaryotes, processed mRNA contains exons after introns are removed; tRNA and rRNA are not described in terms of exons in basic exam questions. Step 5: For description e (is a component of ribosomes) and f (is the most abundant RNA), recall that rRNA molecules form the core of ribosomes and are the most abundant type of RNA in cells, so both refer to rRNA. Step 6: Combine these matches: a and d – tRNA; b and c – mRNA; e and f – rRNA. This corresponds exactly to option a.

Verification / Alternative check:
To double check, think of some standard facts: tRNA is often illustrated with a cloverleaf structure showing an anticodon and an amino acid attachment site. mRNA is depicted as a linear strand with codons that determine protein sequence, and in eukaryotes it is processed to remove introns, leaving exons. rRNA is drawn as part of the large and small ribosomal subunits and is repeatedly described as the most abundant RNA. Since these textbook descriptions line up perfectly with the mapping in option a, we can be confident that option a is correct.

Why Other Options Are Wrong:
Option b misassigns anticodons or exons to the wrong RNA types and therefore cannot be correct. Option c incorrectly links anticodons with rRNA and exons with tRNA, which contradicts standard definitions. Option d mixes up roles of tRNA, mRNA and rRNA in a way that does not match actual cell biology. Option e states that none of the classifications is correct, which is clearly false because we have found a consistent and accurate mapping in option a. Thus, options b, c, d and e all fail to match descriptions a–f correctly.

Common Pitfalls:
Students sometimes confuse mRNA and tRNA because both are involved in translation at the ribosome. A typical error is to forget that anticodons belong to tRNA, not mRNA, and that exons are a feature of processed mRNA, not of tRNA or rRNA. Another pitfall is to forget which RNA type is most abundant; many assume mRNA, but rRNA actually dominates by mass. To avoid these mistakes, remember three key associations: tRNA equals anticodon plus amino acid, mRNA equals codons plus exons and rRNA equals ribosome plus most abundant. These simple links help you quickly sort such descriptions correctly.

Final Answer:
The correct classification is a and d – tRNA; b and c – mRNA; e and f – rRNA, which is given in option a.