4.2.1 The Genome

Key Features of the Genome:

1. Definition of a Genome:

• A genome is the entire set of DNA in a cell, including all the genes and non-coding regions.
• It contains instructions needed for the growth, development, and functioning of an organism.

2. Variation in Genome Size:

• The genome size can vary between organisms. For instance:
• Prokaryotes: Have smaller genomes with mostly coding DNA.
• Eukaryotes: Have larger genomes with a significant proportion of non-coding DNA.

3. Coding and Non-Coding Regions:

• Coding regions (exons): Encode proteins or functional RNA.
• Non-coding regions: Include introns, regulatory sequences, and repetitive DNA.

4. Mitochondrial and Chloroplast DNA:

• Mitochondria and chloroplasts have their own small circular DNA, separate from nuclear DNA.
• These organelles are inherited maternally in most organisms.

5. The Human Genome Project:

• A major scientific initiative that mapped the entire human genome, identifying all the genes and their locations.
• This has improved our understanding of genetic diseases and paved the way for personalised medicine.

Key Terms:

• Genome: The entire set of genetic material in an organism.
• Exons: Coding sequences in the DNA.
• Introns: Non-coding sequences in the DNA.
• Regulatory sequences: Regions of DNA that control gene expression.