Chromosome 11 Flyover (Part 3): Ubiquilin 3 and LOC genes affecting smell, 3D animation
Just as we chart the world around us, we can map human chromosomes. The features of chromosomes can include protein-coding genes, ancient molecular parasites known as transposons, or stretches of repeat sequences.
In this section, take a guided tour of less than 1% of your genetic material to see new and unusual views of your chromosomal landscape.
(DNAi location: Genome > Tour > Flyover > Ubiquilin and olfactory receptor cluster)
The intergenic region is followed by two adjacent ubiquilin genes, which are involved in key cell processes, from replication to "programmed" death. Ubiquilin 3 is expressed specifically in the testis, where it is believed to help regulate sperm development. These are followed by a cluster of gene locations (LOC) thought to encode olfactory receptors, which receive stimuli in the nose to allow us to detect smells. At 31,110 nucleotides long, the first gene in this cluster, LOC120009, is the longest we will encounter on our journey. Its 11 coding exons are indicated in red, but most of its bulk comes from its yellow introns and 29 blue and purple transposons. However, the majority of olfactory receptors are short. The next four gene locations are more typical of olfactory receptors in having only one or two coding exons. About 60% of our smell receptors are nonfunctional. Presumably, humans have less need for smell in locating food and interacting socially. The mutations that inactivate many receptors vary among people, meaning that there is a DNA basis for the observation that some people can smell better than others! It also suggests that the loss of smelling acuity has occurred very recently in human evolution and is still ongoing.