4.1.7 Non-Coding DNA

Key Features of Non-Coding DNA:

1. Introns and Exons:

• Exons are the coding regions of DNA that specify amino acid sequences in proteins.
• Introns are the non-coding regions of DNA found within genes. These are transcribed into RNA but are removed during RNA processing.

2. Functions of Non-Coding DNA:

• Introns and other non-coding DNA do not code for proteins but play regulatory roles, such as controlling gene expression.
• Some non-coding DNA regions are involved in the production of functional RNA, such as tRNA and rRNA.
• Non-coding sequences like telomeres protect the ends of chromosomes from damage.

3. Regulatory Sequences:

• Non-coding regions include promoters, enhancers, and silencers, which regulate the transcription of nearby genes.

4. Repetitive DNA:

• A significant portion of non-coding DNA is made up of repetitive sequences. These can be involved in maintaining chromosome structure or have unknown functions.

5. Prokaryotic DNA vs Eukaryotic DNA:

• In prokaryotic cells, DNA generally lacks introns and non-coding sequences.
• In eukaryotic cells, introns are common, and a large proportion of the genome is non-coding.

Key Terms:

• Introns: Non-coding regions of a gene.
• Exons: Coding regions of a gene.
• Promoters: Non-coding regions where RNA polymerase binds to initiate transcription.
• Enhancers/Silencers: Non-coding regions that increase or decrease the rate of transcription.