Final answer:
rRNA genes in higher eukaryotes are organized into clusters within nucleolar organizer regions, with humans having around 400 per cell to ensure sufficient ribosome production. The sequences of these genes are kept identical through concerted evolution, which includes mechanisms like gene conversion to maintain ribosome assembly and function.
Step-by-step explanation:
In higher eukaryotes, rRNA genes are organized into clusters known as ribosomal DNA (rDNA) repeats. These clusters can be found in the nucleolar organizer regions of certain chromosomes. While the number of rRNA genes per cell can vary among different species, it's common for a human cell to have approximately 400 rRNA genes distributed across five chromosomes. This high number of genes is necessary to meet the cellular demand for ribosome production, which is critical for protein synthesis.
The sequences of individual rRNA genes are kept virtually identical through a homogenization process known as concerted evolution. This process involves mechanisms such as unequal crossing over and gene conversion during meiosis. These mechanisms correct mutations that could cause variations in the rRNA genes, thus maintaining the uniformity essential for the proper assembly and function of ribosomes.
Differences in chromosomal structures between prokaryotes and eukaryotes, the genetic sequence as a blueprint of an organism, and the roles of tRNA and rRNA all contribute to our understanding of the importance of the conservation of rRNA gene sequences.