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  • Hi. It's Mr. Andersen and welcome to biology essentials video 53. This is on

  • environmental genotype effects. In other words, how the environment can effect genotypes.

  • Now remember genotypes are the genes that you have. But how those are expressed is called

  • your phenotype. So what you physically look like is your phenotype. But the genotype are

  • the genes that lie behind that. In other words, that make those proteins. That make your physical

  • appearance. And so basically as the environment changes, you can either express genes or not.

  • And so this is the Himalayan rabbit or at least a cartoon version of a Himalayan rabbit.

  • Himalayan rabbits are all black. But if you look at the picture, it's not all black. And

  • so basically what a Himalayan rabbit is doing is it's expressing the gene to make melanin

  • which causes the coloration that's black. However since the core of the body of the

  • Himalayan rabbit is warm, it disrupts the expression of that genotype. So you can't

  • make the melanin. And so the areas on a Himalayan rabbit that are cooler, that are away from

  • that core are actually able to be that black phenotype. And so you might not buy it. And

  • so this is a cool study that was done with Himalayan rabbits. Basically you shave the

  • Himalayan rabbit's back. So you get rid of all the fur on the back. And then you add,

  • not ice, but an ice pack to the back of Himalayan rabbit. And then you let it sit on there as

  • the hair grows back in. And when the hair browns back in, what you'll have is a black

  • patch wherever you shaved. And so what happened was by adding that ice pack you're able to

  • cool the temperature down. And so the core of the body is not able to heat it up. And

  • you can make the melanin that would naturally be there. And so basically you can regulate

  • whether or not that genotype is going to be expressed. I've always thought it would be

  • cool to have a Himalayan rabbit. Then just kind of make my name in its back in black.

  • But that's a little weird. So let's get on to the podcast. What am I going to talk about.

  • Basically I'm going to talk about how traits can be expressed or not. In other words, how

  • the genotypes can be expressed due to changes in the environment. I'll talk about how that

  • occurs in animals. I've mentioned the Himalayan rabbit. But I'll also talk about where that

  • might actually apply in the arctic fox or in the arctic hare. I'll also talk about how

  • plants can change or vary their color due to changes in their environment, notably the

  • pH. And then finally how bacteria can change their expression of genotypes. I'm going to

  • talk about the operon, especially the lac operon. But also show you how in the lab we

  • can use color change in bacteria to see what color or what type of a bacteria you have.

  • So let's start with the animal side and seasonal melanin. So this is an arctic fox. But so

  • is this. And so basically an arctic fox will change its color due to the season. Which

  • totally makes sense. In the winter, when it's snow everywhere, you want them to be white

  • so you can blend in for camouflage. Then in the summer you also want to blend in with

  • your environment. So how do they do that? Well basically they have a pineal gland. The

  • pineal gland sits kind of right in the core of the brain. It's right behind the eyes.

  • And basically it secretes melatonin. Melatonin is a hormone that's created during times of

  • darkness. And so during the winter they're going to secrete more melatonin. As they secrete

  • that melatonin, it's going to trigger the cells in the body not to produce melanin and

  • so they're going to have this white appearance. Now when summer comes. We're going to have

  • a decrease in melatonin. They're going to increase the amount of melanin and they're

  • going to have a dark appearance. And so that's evolved over time. Responding to the environment,

  • those that were able to turn off that melanin during the winter were able to survive longer.

  • And so we're going to see that in the arctic fox. But also the arctic hare. As they change

  • the amount of melanin that they have. And so we're either expressing that gene and having

  • the dark color or we're not expressing the gene. We can also see that same thing in plants.

  • And if you think about plants you might say well, they're always green. And that's the

  • photosynthetic parts. So the leaves obviously are always going to be a green color. That's

  • based on the amount of chlorophyll. But the function of the flower is to attract an animal,

  • notably the insects. And so basically this is the same hydrangea, it's the same species

  • of plant, but it's able to get different colors of flowers. And it's doing that in response

  • to the environment. Notably the soil environment. And so basically these ones are cultivated

  • by humans, but they can vary the pH of the soil. And if you have a pH in the 6s, then

  • you get this pink hydrangea. If lower the pH into the 5s you can get this blue hydrangea.

  • Basically the blue is coming from aluminum that when the pH gets lower their able to

  • pick up and then express that. And so the genes that they're making are dependent upon

  • what building blocks they have. In this case in their environment, whether they can express

  • it or not. So it's not like they're turning it on or off. But they're able to vary the

  • amount of coloration. And so that's going to give them variation in their environment.

  • Last thing I want to talk about was bacteria. And how bacteria can either express genotypes

  • or not. And when I say express it or not, the one thing that should jump to mind is

  • operons in bacteria. Remember basically in bacteria they have a string of genes that

  • are right next to each other. They can turn it on or they can turn it off. In this case

  • there are three genes that help the breakdown of lactose. And so you basically have a promoter

  • where RNA polymerase can get on. You can either make those or not. Dependent upon the presence

  • of lactose. If this makes no sense, make sure you watch the podcast on gene regulation.

  • But if you have this, then you're called lac positive. If you have the lac operon you have

  • this whole thing. If you don't have it, then you're lac negative. And so you're a bacteria

  • that can't breakdown lactose. And so a good way to differentiate between those that are

  • lac positive and those that are lac negative is using somethingcalled MacConkey Agar. So

  • you're growing colonies of bacteria on it. Basically you grow the bacteria. They'll grow

  • on this. They'll feed on the agar. They'll multiply over time. So you know 24 hours later

  • you have all these bacteria. But in the MacConkey Agar it's innovative. What they do is they

  • put a chemical in here that can sense the pH. Because if you're lac positive you're

  • going to make acids that are going to change the pH in the agar. And so basically they

  • put an indicator, is the word I was thinking of, that once the pH goes below 6.8 then it's

  • going to have a pink coloration or pink appearance. And so if you grow bacteria on MacConkey Agar,

  • so you can see over here we have bacteria that a lac negative. Because they don't have

  • that lac operon. Over here we have e. coli that are lac positive. And since they're breaking

  • down that lactose that's also found in the agar then they're lowering the pH and now

  • the indicators going to give it that pink appearance. And so it's just an example of

  • how a gene is either expressed and we see a phenotype. In this case that phenotype that

  • we don't necessarily see in the lac open we can actually see in the agar. And so that's

  • basically how an environment can effect genotypes. Can effect what phenotypes we see. And I hope

  • that's helpful.

Hi. It's Mr. Andersen and welcome to biology essentials video 53. This is on

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遺伝子型表現 (Genotype Expression)

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    Ancodot に公開 2021 年 01 月 14 日
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