Did you know that nectarines are just peaches with an old school mutation?
Nectarines are really just peaches without the fuzz, or with hairless or glabrous skin.
And that fuzz, or lack thereof, is controlled by a single gene. A homozygous recessive allele.
Today... we're going to find it
I went to the farmers market, and with all the determination, and lack of self-consciousness of a scientist,
found both peaches and nectarines of different varietals to sample. Five of each.
I took them back to the lab, and took... "careful" samples of the fruit.
Now that we have our fruit samples, we have to extract their DNA.
You may have seen strawberry DNA extractions before, or even my own cheek cell extraction many videos ago.
Well the kit that I'm using in lab works by a pretty similar principle, break open cells, get DNA, wash DNA.
This is just far more standardised and clean. Now that we have our DNA, we're going to look for the fuzz causing gene.
And here's where I'm going to back up a step.
[Alex walking]
Fruit farmers have known for a long time, that the fuzzless nectarine was caused by a recessive allele.
You can click... here, to find out more about recessive and dominant alleles.
The short version, is that you have two copies of every gene, and these can have different variations, or alleles.
Peaches also have 2 copies of every genes. Here we are dealing with a gene involved in peach fuzz formation, and there is an allele that causes fuzz,
and an allele that doesn't cause fuzz.
Now some alleles are stronger than others, and are referred to as... 'dominant'. Dominant alleles are stronger than recessive alleles.
So if fuzz is dominant over not fuzz, a peach with 2 copies of the fuzz allele, will be fuzzy...
2 copies of the not fuzzy allele... not fuzzy,
but 1 fuzz allele and 1 not fuzz allele... still fuzzy, because the fuzz allele is dominant.
Now a 2014 paper from an Italian research group, looked into what could have cause these fuzzy and not fuzzy alleles.
They found that in nectarines, long piece of DNA had been inserted into a gene predicted to be involved, with making some of this hairy fuzz.
This extra, long piece of DNA, mucked up the gene, and caused a loss of function, meaning the gene could no longer contribute to fuzz production.
Peaches with 1 intact copy, are still okay, but 2 mucked up copies, and there's just no fuzz.
By looking at different nectarine varieties across the world, this group also proposed that this DNA insertion happened, in a single event, thousands of years ago,
and was then spread... around the world, by humans, spreading nectarines.
So, how can we see the fuzzy or not fuzzy alleles, in our peach DNA?
Well, we're going to have to amplify our DNA somehow...
somehow, with PCR.
'PCR', or 'Polymerase Chain Reaction', really deserves it's own magnum opus of a video.
But in short, we are selectively copying and amplifying a region of DNA.
We specify which piece we want to copy, by adding tiny strips of DNA, called 'primers'...
that match-up to the outside edges, of the regions we want.
Now we're going to use that DNA insertion, to our advantage here.
That 2014 paper described primers that would amplify the region around the insertion.
One set of primers, amplifies the normal, not inserted DNA. It make a chunk of DNA that is 941 base pairs long,
but one more primer added into the mix, amplifies a shorter version, only if that insertion is there.
So the nectarine allele will amplify a little chunk of DNA, while the fuzzy peach allele will amplify a bigger chunk.
I have DNA. I have primers, and I have polymerase... PCR time.
["Kawai Kitsune" by Kevin MacLeod]
After PCR, in each tube, I have either short, nectarine, indicative chunks, or long, peach, indicative chunks.
But, how am I going to see them?
This is an agarose gel.
Made from a polysaccharide, 'agarose', extracted from seaweed, it forms a meshy gel.
Big pieces of DNA move slowly through the gel, because they get suck in the mesh of molecules, while little pieces of DNA can zip right through all the holes.
This allows us to separate DNA by size.
We load our samples into the top of the gel, then we use electricity to move the DNA through the gel.
The negatively charged DNA will move from the negatively charged side of the gel box, to the positively charged side.
After about a hour, with the help of a special dye and UV light, we can take a picture of our gel.
You can see in the picture that I also added a 'ladder', a bunch of fragments that I know what the DNA size is, so I can compare that sizes of my fragments...
And it worked...
Nothing in lab ever works on the first try.
You can see the nectarines have all these tiny chunks of DNA, that moved really far in the gel,
while the peaches have these big chunks,
and some of the peaches have... both, which means they're... 'heterozygous', or they have one each of the fuzz and not fuzz alleles,
while the rest of the peaches and nectarines are 'homozygous', meaning they have two of the same allele.
This is so cool to me! I love knowing the genetics behind everyday stuff around me, and this is totally the story I will tell at every barbecue I go to this summer.
And you should too.
Go forth! And talk about science!
Also a couple summers ago, I made a video about the genetics behind seedless watermelons, which you can check out... over there.
Because apparently something about the summer makes me want to talk about plant biology.
So if there's anything... any cool... plant, or animal, or food, or... bacteria,
or any sort of cool, summery genetic story you want me to talk about before the summer is over,
leave your suggestions in the comments below.
"Suggestions", "suggestions", leave me your "suggestions" in the comments below, and maybe I will make a video about it,
because summer time... is for summer science.
["Kawai Kitsune" by Kevin MacLeod]