* Vast Diversity: Mammals are a highly diverse group with a wide range of genome sizes. A tiny shrew will have a drastically different number of base pairs than a blue whale.
* Gene Definition: Even within a single species, defining exactly what constitutes a "gene" is complex. There are protein-coding genes, non-coding RNA genes, and various regulatory regions that might be considered part of a gene.
* Ongoing Research: Scientists are still actively studying and annotating genomes. New genes are discovered, and the boundaries of existing genes are refined constantly.
Instead of a specific number, here's some information about mammalian genomes:
* Human Genome: The human genome has approximately 3 billion base pairs. This is a reference point, but it's not representative of all mammals.
* Genome Size Variation: The size of mammalian genomes can vary tremendously. For example, the genome of the lungfish is much larger than the human genome.
* Gene Number Variation: While the total number of base pairs varies, the number of protein-coding genes within a genome can be surprisingly similar across species. This suggests that differences in genome size are often due to non-coding DNA.
To summarize, while we can't give an exact number for all mammalian genes, we know that there is significant variation in genome size and gene number across different mammalian species.
