4.1.4 Genes

Key Features of Genes:

1. Definition:

• A gene is a length of DNA that provides the instructions to produce:
• Polypeptides, which fold to form proteins.
• Functional RNA, such as ribosomal RNA (rRNA) and transfer RNA (tRNA).

2. Structure:

• Genes consist of coding regions called exons, and non-coding regions called introns in eukaryotes.
• The sequence of bases (adenine, thymine, cytosine, guanine) in a gene determines the amino acid sequence in a polypeptide.

3. Location:

• Found on chromosomes, with each gene occupying a specific locus (position).

4. Genetic Code:

• The genetic code in a gene is:
• Universal: The same code is used in almost all living organisms.
• Degenerate: Multiple codons can code for the same amino acid.
• Non-overlapping: Each codon is read separately.

5. Role in Protein Synthesis:

• Genes are transcribed into messenger RNA (mRNA) during transcription.
• mRNA is then translated into polypeptides during translation.

Key Terms:

• Gene: A segment of DNA that codes for a polypeptide or functional RNA.
• Exons: Coding regions of a gene.
• Introns: Non-coding regions of a gene, removed during RNA splicing.
• Locus: The specific position of a gene on a chromosome.
• Genetic Code: The sequence of bases in DNA that determines amino acid sequences.