Question

RECALL Define exon and intron.

Short answer

Exons code for proteins, introns do not.

Step-by-step solution

Define the Term 'Exon'

An exon is a segment of a DNA or RNA molecule containing information coding for a protein or peptide sequence. In simple terms, exons are the sequences in the genetic code that are expressed and translated into proteins.

Define the Term 'Intron'

An intron is a segment of a DNA or RNA molecule that does not code for proteins and interrupts the sequence of genes. Introns are removed from the pre-mRNA during the process of RNA splicing.

Summarize the Key Differences

The key difference between exons and introns is that exons code for proteins, while introns do not. Exons are retained in the final mRNA molecule, but introns are spliced out before translation.

Key concepts

Exon

Exons are crucial parts of your DNA and RNA. They contain the information needed to code for proteins or peptides. Think of exons as the **important parts** of a genetic message. When your body needs to make a protein, it reads the exons, which guide the process of building that protein.
Exons are expressed sequences, meaning they are translated into functional proteins. They are retained in the final mRNA sequence after the RNA molecule undergoes processing.

Intron

Introns are segments in the DNA or RNA that do not code for proteins. These sequences interrupt genes and are typically removed before protein synthesis.
Introns are like the **extra bits** in a genetic sequence – parts that are present in the initial RNA transcript but are removed during RNA splicing. Although they are not used to make proteins, introns have important roles in gene regulation and evolution. They contribute to the diversity of protein products by allowing for alternative splicing.

RNA Splicing

RNA splicing is the process by which introns are removed from the pre-mRNA (precursor mRNA). Once the introns are cut out, the remaining exons are joined together to form a mature mRNA molecule.
This mature mRNA is then ready for translation into a protein. Think of RNA splicing like editing a rough draft. The unnecessary parts are removed, leaving only the sequences that provide useful information.
Essential steps in RNA splicing:

• Recognition of introns and exons in the pre-mRNA
• Cutting out the introns
• Connecting the exons together

This results in a seamless, functional mRNA ready for protein synthesis.

Genetic Code

The genetic code is the set of rules by which information encoded in DNA or RNA sequences is translated into proteins by living cells.
It is universal, meaning it's the same in almost all organisms. The genetic code consists of sequences of three nucleotides, known as 'codons,' each of which corresponds to a specific amino acid or a stop signal during protein synthesis.
Key features of the genetic code:

• It is made up of codons, each three nucleotides long
• Each codon codes for one specific amino acid
• There are start and stop codons that signal the beginning and end of protein synthesis

The genetic code ensures that genetic information is accurately translated into the proteins necessary for life.