Question

Rank the following in order of size: tRNA, DNA, mRNA.

Short answer

Ranked by size: tRNA < mRNA < DNA.

Step-by-step solution

Introduction to Nucleic Acids

The first step is to understand the basic types of nucleic acids involved: tRNA (transfer RNA), DNA (deoxyribonucleic acid), and mRNA (messenger RNA). Each of these nucleic acids has distinct roles and structures in biological systems.

Understanding Structure and Function

tRNA is involved in translating the genetic code from mRNA into proteins and is relatively small in size, usually around 76-90 nucleotides in length. DNA, which contains the genetic blueprint of organisms, forms longer, double-stranded helices with millions of base pairs. mRNA, which carries genetic information from DNA to the ribosome, varies widely in length but is generally larger than tRNA, comprising hundreds to thousands of nucleotides.

Comparing Sizes

To rank them by size, consider that tRNA is the smallest, with about 76-90 nucleotides; next is mRNA, which is usually longer because it encodes entire proteins; and DNA is the largest, most extended molecule as it encapsulates entire genomes. The order from smallest to largest based on average size is: tRNA < mRNA < DNA.

Key concepts

tRNA structure

Imagine tiny transporters in the cell that help build proteins, that's tRNA for you. Transfer RNA (tRNA) plays a pivotal role in the translation process, converting genetic instructions into proteins. It carries specific amino acids to ribosomes during protein synthesis.
Unlike DNA and mRNA, tRNA is relatively small and consists of about 76 to 90 nucleotides. This compact size helps it efficiently interact with both mRNA and ribosomes.
A tRNA molecule looks a bit like a four-leaf clover when flattened out. It has an 'anticodon loop' that matches specific mRNA codons. This unique structure ensures that the correct amino acids are linked together to form a protein chain.
In a nutshell, tRNA might be small, but it’s crucial for deciphering the genetic code into functional proteins.

mRNA function

Messenger RNA (mRNA) is your cell’s way of passing messages from DNA to ribosomes, the protein-making machines. Thus, its name - messenger RNA. This type of nucleic acid carries the blueprint for protein synthesis. It transfers information found in DNA to the ribosome, where proteins are synthesized.
Unlike tRNA, mRNA can vary greatly in size because it is tailored to different lengths of genetic code; some might span several thousand nucleotides. It is complementary to one of the DNA strands, ensuring the code is correctly translated. Without mRNA functioning as a messenger, the genetic information encoded in DNA would be of no functional use.
Among its duties:

• Copies the genetic code from DNA through a process called transcription.
• Serves as a template for assembling amino acids into proteins during translation.

The structure of mRNA, with a cap and tail, assists in stability and regulation of protein synthesis, showing how crucial this molecule is in gene expression.

DNA size comparison

DNA, or deoxyribonucleic acid, is like a massive archive of genetic information. It's substantially longer and larger than both tRNA and mRNA. When visualized, DNA's double helix structure contains millions of base pairs.
This length is because DNA holds the complete set of genetic instructions for the organism – that's a lot of information to store!
The size of DNA can be understood when compared to tRNA and mRNA. While tRNA is composed of only 76-90 nucleotides, and mRNA ranges anywhere from a few hundred to thousands of nucleotides, DNA stretches to an immense size with its double-stranded helical structure containing millions of nucleotide pairs.
In brief, in terms of size:

• tRNA is the smallest.
• mRNA is larger than tRNA.
• DNA is the largest, as it encompasses entire genomes.

DNA's extensive size allows it to encapsulate the entire genetic makeup of an organism – a true marvel of biological complexity and efficiency.