Final answer:
Mammalian genomes have a CpG content of about 1%, notable for its role in gene regulation. We find common DNA sequences among humans, macaques, and mice through genomic database searches, supporting the idea of a common ancestry. The human genome is extensive, with the majority of its sequence involved in regulatory functions beyond encoding proteins.
Step-by-step explanation:
The approximate CpG content in mammalian genomes is lower than might be expected by chance, due to the high rate of mutation of cytosine to thymine in the CpG dinucleotide. In general, mammalian genomes, including humans, are characterized by having a CpG content around 1% of the total base pairs. This is significant because CpG sites are often found in regulatory regions of genes and are subject to methylation, which affects gene expression levels. These CpG sites are underrepresented in the overall genome, but can form 'CpG islands' in promoter regions where they have functional roles.
When it comes to identifying common DNA sequences among different species such as humans, macaques, and mice, it is evident that there are indeed shared sequences. These sequences can sometimes be identified using gene or phenotypic characteristic searches in genomic databases. Such comparisons support the hypothesis that these mammals share a common ancestor, as evidenced by similar sequences and shared regulatory domains among their genes.
An example of conserved sequences is the protein cytochrome c, where certain amino acids are found in the same position across different species, highlighting the evolutionary relationships amongst them. Another point of interest is that the human genome is vast, consisting of over 3 billion base pairs, of which only around 1-2% encode for proteins. The rest of the genome contains regulatory sequences, non-coding RNA, and introns.