|Cats taste the world very differently than humans|
The gene that we looked at was one of the two that go into making the receptors on your tongue that register sweetness. Specifically, the TAS1R2 (taste receptor, type 1, member 2) gene. TAS1R2 must join up with a second protein to signal that sweet flavor. Here is the TAS1R2 gene (specifically, my copy) in its three hundred fifty-five nucleotide entirety:
GCTGCGTACCACACCCAGCGCCGACCACCACATCGAGGCCATGGTGCAGCTGATGCTGCACTTCCGCTGGAACTGGATCATTGTGCTGGTGAGCAGCGACACCTATGGCCGCGACAATGGCCAGCTGCTTGGCGAGCGCGTGGCCCGGCGCGACATCTGCATCGCCTTCCAGGAGACGCTGCCCACACTGCAGCCCAACCAGAACATGACGTCAGAGGAGCGCCAGCGCCTGGTGACCATTGTGGACAAGCTGCAGCAGAGCACAGCGCGCGTCGTGGTCGTGTTCTCGCCCGACCTGACCCTGTACCACTTCTTCAATGAGGTGCTGCGCCAGAACTTCACTGGCGCCGTGTGG...not really that interesting.
This is your average TAS1R2 gene for Homo sapiens, nothing special. Just about every human out there has this exact sequence, with few exceptions (one of my classmates, for example, had a single point mutation). However, it is one gene crucial to why humans like sweets so much. This is what the gene looks like after it's been translated into its protein form (the letters are standard for amino acids):
This is a comparison showing my own protein versus the average human. It's a perfect match and codes for a fully functional receptor protein. This gene is seen in a very wide variety of different animals, and the shared genetic material is quite astounding, allowing for countless species to have the ability to taste sweetness.Query 2 LRTTPSADHHIEAMVQLMLHFRWNWIIVLVSSDTYGRDNGQLLGERVARRDICIAFQETL 181 LRTTPSADHHIEAMVQLMLHFRWNWIIVLVSSDTYGRDNGQLLGERVARRDICIAFQETL Sbjct 82 LRTTPSADHHIEAMVQLMLHFRWNWIIVLVSSDTYGRDNGQLLGERVARRDICIAFQETL 141 Query 182 PTLQPNQNMTSEERQRLVTIVDKLQQSTARVVVVFSPDLTLYHFFNEVLRQNFTGAVW 355 PTLQPNQNMTSEERQRLVTIVDKLQQSTARVVVVFSPDLTLYHFFNEVLRQNFTGAVW Sbjct 142 PTLQPNQNMTSEERQRLVTIVDKLQQSTARVVVVFSPDLTLYHFFNEVLRQNFTGAVW 199
|A cat enjoying a fresh fish|
So, why am I talking about humans a post about cats? Well, let's compare the sequence above to the equivalent gene in a cat. The "query"line is the human gene again, and the "sbjct" or subject line is the equivalent gene in Felis silvestris catus.
Query 2 LRTTPSADHHIEAMVQLMLHFRWNWIIVLVSSDTYGRDNGQLLGERVARRDICIAFQETL 181 LRT P+ +H AM ++ +FRWNW+ + + D YGR + E RDICI F E + Sbjct 184 LRTIPNDEHQATAMADIIEYFRWNWVGTIAADDDYGRPGIEKFREEAEERDICIDFSELI 243 Query 182 PTLQPNQNMTSEERQRLVTIVDKLQQSTARVVVVFSPDLTLYHFFNEVLRQNFTGAVW 355 +Q EE Q++V ++ Q STA+V+VVFS L E++R+N TG +W Sbjct 244 -----SQYSDEEEIQQVVEVI---QNSTAKVIVVFSSGPDLEPLIKEIVRRNITGRIW 293
|Cat tongue anatomy|
Though cats aren't able to taste sweetness, this doesn't mean they will avoid it. They are, in fact, completely indifferent to the flavor. So, if your kitty likes something sweet, it's probably going after something other than the sugar. They're quite fond of certain amino acids, so it's possible that's what your kitty enjoys.
Sources Basic Local Alignment Search Tool (BLAST), PLOS Genetics, Journal of Nutrition, and GeneCards. Images are from Wikimedia Commons under Creative Commons licenses: one, two, three.
By the way, BLAST is an amazing tool. Feel free to plug in the ATCG sequence above into their databases to compare the gene for yourself. The programs I used for this post are nucleotide blast and blastx.