Genomic Structure and Evolution of Multigene Families : “Flowers” on the Human Genome

Abstract EN

We report the results of an extensive investigation of genomic structures in the human genome, with a particular focus on relatively large repeats (>50 kb) in adjacent chromosomal regions.

We named such structures “Flowers” because the pattern observed on dot plots resembles a flower.

We detected a total of 291 Flowers in the human genome.

They were predominantly located in euchromatic regions.

Flowers are gene-rich compared to the average gene density of the genome.

Genes involved in systems receiving environmental information, such as immunity and detoxification, were overrepresented in Flowers.

Within a Flower, the mean number of duplication units was approximately four.

The maximum and minimum identities between homologs in a Flower showed different distributions; the maximum identity was often concentrated to 100% identity, while the minimum identity was evenly distributed in the range of 78% to 100%.

Using a gene conversion detection test, we found frequent and/or recent gene conversion events within the tested Flowers.

Interestingly, many of those converted regions contained protein-coding genes.

Computer simulation studies suggest that one role of such frequent gene conversions is the elongation of the life span of gene families in a Flower by the resurrection of pseudogenes.