Final answer:
The highest average number of nucleotide-pair differences per 1000 nucleotide pairs would likely be between the genomes of S. cerevisiae (yeast) and M. musculus (mouse), as they are from very different evolutionary branches, leading to substantial differences.
Step-by-step explanation:
The student is asking which pair among the given options shows the highest average number of nucleotide-pair differences per 1000 nucleotide pairs. Genomic differences can significantly vary depending on evolutionary distance, the prevalence of conserved sequences, and genetic diversity among species. Considering these factors:
- S. cerevisiae (yeast) and M. musculus (mouse) are from very different evolutionary branches, with yeast being a unicellular eukaryote and the mouse being a mammal. Therefore, the genomic differences between these two organisms are expected to be quite substantial.
- Differences between two E. coli strains would be much smaller as they are of the same species.
- Genomic differences between humans and E. coli in ribosomal RNA genes are marked due to the significant evolutionary distance between eukaryotes and prokaryotes.
- The comparison of transfer RNA genes in a human and a mouse will show some differences but to a lesser extent since both are mammals.
- The genomes of two humans will be the most similar out of the options provided with minimal differences (mostly SNPs).
Based on the provided information and the understanding of genetic diversity and evolutionary biology, the pair which shows the highest average number of nucleotide-pair differences per 1000 nucleotide pairs would likely be the genomes of S. cerevisiae and M. musculus due to their significant evolutionary separation.