8.3.3 Non-Coding DNA & Regulatory Genes

What is Non-Coding DNA?

• Non-coding DNA refers to regions of DNA that do not code for proteins.
• Instead of being transcribed into mRNA for protein production, non-coding DNA plays roles in regulating gene expression.

Functions of Non-Coding DNA

1. Regulatory Roles:

• Non-coding DNA contains promoters, enhancers, and silencers that control when and how genes are transcribed.
• These regions influence which genes are switched on or off in different cell types or under different conditions.

2. RNA Molecules:

• Some non-coding regions are transcribed into functional RNA molecules, such as tRNA, rRNA, and microRNA (miRNA), which regulate gene expression or assist in protein synthesis.

3. Structural DNA:

• Non-coding regions contribute to the structure of chromosomes, such as telomeres (protective caps at the ends of chromosomes) and centromeres (important during cell division).

Regulatory Genes

• Regulatory genes code for proteins such as transcription factors, which control the activity of other genes by binding to DNA.
• These genes determine whether a specific gene is transcribed into mRNA, affecting protein production.

Challenges in Translating Genomes into Proteomes

1. Selective Gene Expression:

• Not all genes are active in every cell at all times.
• Genes are selectively expressed depending on the cell type, developmental stage, or environmental conditions.

2. Complexity in Eukaryotes:

• In higher organisms, a significant proportion of the genome is non-coding DNA, making it difficult to predict the proteome (all proteins a genome can code for).

3. Alternative Splicing:

• A single gene can produce multiple proteins through alternative splicing, where different combinations of exons are joined.