Question

Define exon and intron.

Short answer

Exons are coding segments of DNA/RNA, and introns are non-coding segments that are removed during RNA processing.

Step-by-step solution

Define Exon

An exon is a segment of a DNA or RNA molecule containing information for coding a protein or peptide sequence. Exons are the sequences that remain in the RNA after premature RNA (hnRNA) undergoes processing.

Define 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 RNA during the RNA processing to produce the final mature RNA.

Key concepts

DNA

DNA, or deoxyribonucleic acid, is the molecule that carries the genetic instructions for life. It's a double helix structure composed of nucleotides, which include a phosphate group, a sugar group, and a nitrogen base. The four nitrogen bases are adenine (A), thymine (T), cytosine (C), and guanine (G). These bases pair specifically (A with T and C with G) to form the rungs of the DNA ladder. DNA not only stores genetic information but also dictates the sequence of amino acids in proteins through the processes of transcription and translation.

RNA processing

RNA processing transforms a primary RNA transcript into a mature RNA molecule, ready for translation into a protein. This process involves several steps:

• Splicing: This includes the removal of introns (non-coding regions) and the joining of exons (coding regions).

• 5' Capping: A modified guanine nucleotide is added to the beginning of the RNA transcript to protect it from degradation.

• Polyadenylation: A tail of adenine nucleotides is added to the 3' end of the RNA molecule. This poly-A tail helps in the stability and export of the mRNA.

All these modifications prepare the RNA to direct the synthesis of proteins accurately.

Protein coding

Protein coding refers to the process by which a sequence of DNA or RNA is translated into a protein. During transcription, a specific segment of DNA is copied into RNA. In eukaryotic cells, after RNA processing, the mature mRNA leaves the nucleus and goes to the ribosome. There, the mRNA is translated into a chain of amino acids, which then folds into a functional protein. The specific sequence of the nucleotides in the mRNA determines the order of amino acids in the protein, which ultimately determines its structure and function.

Gene sequence

A gene sequence is an order of nucleotides in DNA that codes for a functional product, usually a protein. Each gene has regulatory regions (which help control gene expression) and coding regions (exons) separated by non-coding regions (introns). Understanding gene sequences is crucial because:

• It reveals how genes govern biological traits and functions.

• It helps in identifying genetic mutations that may lead to diseases.

• It is fundamental in biotechnological applications like gene editing and synthetic biology.

By studying gene sequences, scientists can better understand the complexities of heredity, organism development, and physiology.