Question

Discuss the structure and organization of the mitochondrial and chloroplast genomes. How large are they, how many genes do they contain, and how many copies of the genome are found in each organelle?

Short answer

The mitochondrial genome is much smaller than the chloroplast genome, with 16,569 base pairs and 37 genes in humans compared to 120,000-170,000 base pairs and about 120 genes in chloroplasts. The number of genome copies per organelle is variable, but most cells contain multiple copies of both the mitochondrial and chloroplast genomes.

Step-by-step solution

Understanding Genome Structure - Mitochondria

Mitochondrial genomes are generally quite small compared to nuclear genomes. The human mitochondrial genome, for instance, contains 16,569 base pairs (bp). The genome is circular in structure and contains 37 genes: 13 protein-coding genes, 22 transfer RNA genes, and 2 ribosomal RNA genes.

Understanding Genome Structure - Chloroplasts

The chloroplast genome is larger than the mitochondrial genome, it contains between 120,000 and 170,000 bp. Like the mitochondrial genome, it also has a circular structure. In general, chloroplast genomes contain about 120 genes, including those for photosynthesis proteins, ribosomal RNA, transfer RNA, and other proteins.

Comparing Genome Copies in Each Organelle

The number of genome copies per organelle varies greatly and depends on the type and stage of the cell. Most cells contain many copies of the mitochondrial genome; some estimates suggest anywhere from 2 to 10 copies per mitochondrion. The number of chloroplast genomes is also variable, ranging from less than a hundred to several thousand, depending on the plant species and the age and type of the cell.