Appropriate forum would be "Biological Evolution".
For this topic, I would like to discuss the viability of microRNA's (miRNA) as an accessible piece of evidence for evolution.
miRNAs has several attractive features for these types of discussions.
1. Short sequence (~90 nucleotides).
2. High conservation between species.
3. Accessible online tools for viewing miRNA sequences.
A gene can be tens of thousands of bases long with multiple introns and exons. miRNAs can be viewed in a large font in a single line. This alone makes them more accessible to the average person.
One of the difficulties I have found when discussing these topics is aligning DNA sequences for specific genes across specific species. It is doable, but sometimes the effort doesn't seem worth it for these types of discussions. However,
microRNAviewer does all of the heavy lifting when it comes to miRNAs. If you look at the large table at the link above, the left hand column lists the specific miRNA. The row across the top gives the three letter code for different species (e.g. hsa=human, ggo=gorilla, mmu=mouse).
If you click on mir-34 in the left column, it brings you to
this page which shows you the multiple variants of mir-34, and the known sequences for that mir-34 variant in different species.
If you click on mir-34a, you reach
this page, which is the real gist of this thread. Again, you have the three letter codes for each species on the left, and the sequence for mir-34a in the middle of the page. At first, it looks like a bit of a jumble towards the top of the page, with multiple colors, dashes, and letters. However, it is all summarized quite nicely at the bottom of the page, where you see this ASCII figure:
************************** * * *********** * ****
**** ************************** * * * *************** ******* *
** **** ************************** * * * * ************************ ****
***** ** **** **************************** * * * ************************ ****
***** ******** **************************** * * * ************************ ****
***** ******** **************************** * * ** ************************ ****
******************************************* * * **************************** **** *
******************************************** * * ********************************* * *
******************************************** * * ********************************* * * ***
******************************************** * ** ************************************** *** *
******************************************** * ** ************************************** *** **
** ******************************************** **** * ************************************** *** ***
** ******************************************** ****** ************************************** *** ***
*** ******************************************** ****** ****************************************** ***
************************************************ ****** ***********************************************
************************************************* ****** ***********************************************
********************************************************************************************************
********************************************************************************************************
******************************************************************************************************** *
******************************************************************************************************** **
******************************************************************************************************** **
******************************************************************************************************** ****
******************************************************************************************************** *****
**************************************************************************************************************
**************************************************************************************************************
**************************************************************************************************************
**************************************************************************************************************
***************************************************************************************************************
***************************************************************************************************************
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What is this showing? The bottom row of *'s is the human sequence. Each line above it is another species, with the species more closely related to humans towards the bottom, and very distantly related species towards the top. Each * in the row indicates a match to the human sequence. Each gap indicates a difference between the two species.
What you see is that for closely related species the sequence is identical, and you only see differences when you start to look at more distantly related species. What is of much greater interest is where in the sequence you see the differences in those more distantly related species, which will be discussed in later posts.
In further posts we can discuss what miRNAs do, their maturation process, and why only evolution can explain the pattern for both the similarities and differences between miRNAs found in different species.
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