Genotype Expression

Summary

In this Biology Essentials video, Mr. Andersen explores how the environment influences the expression of genotypes, affecting an organism's phenotype. He uses the Himalayan rabbit as an example, where body temperature disrupts melanin production, and discusses similar phenomena in arctic foxes and hares, influenced by melatonin. The video also covers how plants like hydrangeas change flower color based on soil pH, and explains bacterial gene expression through the lac operon and its detection using MacConkey Agar, illustrating the dynamic relationship between genotype and environmental factors.

Takeaways

• 🧬 The environment can influence the expression of genotypes, affecting an organism's phenotype.
• 🐰 Himalayan rabbits naturally express the gene for melanin, but body warmth can disrupt this expression, resulting in a non-black phenotype.
• 🧊 An experiment with Himalayan rabbits showed that cooling the body core with an ice pack can enable melanin production, demonstrating environmental control over gene expression.
• 🦊 The arctic fox and arctic hare change their coat color seasonally, influenced by the hormone melatonin and its production regulated by daylight.
• 🌺 The color of hydrangea flowers can vary based on the pH level of the soil, showing that plants can also exhibit environmental genotype effects.
• 🌱 Plants use their flower colors to attract pollinators, with genes expressing differently depending on environmental factors like soil pH.
• 🦠 Bacteria can regulate the expression of their genotypes, particularly through operons, which are clusters of genes that can be turned on or off in response to environmental conditions.
• 🍦 The lac operon in bacteria is an example of gene regulation where the presence of lactose can turn on genes necessary for lactose breakdown.
• 📏 MacConkey Agar is used in labs to differentiate between lac positive and lac negative bacteria based on their ability to change the pH and color of the agar.
• 🔬 The color change in MacConkey Agar serves as a visible phenotype for bacteria, showing how environmental conditions can affect genotype expression.
• 🌐 Understanding environmental genotype effects is crucial for comprehending how traits are expressed in various species, from rabbits to bacteria.

Q & A

What is the difference between genotype and phenotype?

Genotype refers to the set of genes an individual has, while phenotype is the physical expression of those genes, such as an organism's appearance or characteristics.

How does the environment affect the expression of genotypes?

The environment can influence whether certain genes are expressed or not, leading to variations in an organism's phenotype. For example, temperature changes can disrupt the expression of genes responsible for melanin production in Himalayan rabbits.

What is the significance of the Himalayan rabbit in demonstrating environmental genotype effects?

The Himalayan rabbit serves as an example of how body temperature can affect gene expression. The warm core of the rabbit's body disrupts melanin production, leading to lighter fur in cooler areas, illustrating how environmental factors can alter phenotypes.

How does the study involving shaving a Himalayan rabbit's back and applying an ice pack demonstrate genotype expression?

By shaving the rabbit's back and applying an ice pack, researchers were able to cool the area and allow for melanin production, resulting in a black patch where the fur grew back. This shows that environmental temperature can regulate the expression of the melanin-producing genotype.

What role does the pineal gland play in the color change of arctic foxes?

The pineal gland secretes melatonin, a hormone that is produced more during darkness. Higher melatonin levels in winter trigger the reduction of melanin production, causing the foxes to appear white for camouflage. In summer, lower melatonin levels lead to increased melanin and a darker appearance.

How do arctic foxes and arctic hares adapt their coloration for seasonal camouflage?

Arctic foxes and hares change their fur color based on the season to blend in with their environment. In winter, they have more white fur due to increased melatonin secretion, and in summer, they have darker fur as melatonin levels decrease.

How do plants like hydrangeas change flower color in response to environmental factors?

Hydrangeas can vary their flower color based on the pH level of the soil. A higher pH (around 6) results in pink flowers, while a lower pH (in the 5s) leads to blue flowers due to the uptake and expression of aluminum.

What is the relationship between pH and flower color variation in hydrangeas?

The pH of the soil affects the availability of aluminum, which influences the color of hydrangea flowers. Lower pH levels allow for more aluminum uptake, leading to bluer flowers, while higher pH levels result in pink flowers.

What is an operon and how does it relate to gene expression in bacteria?

An operon is a group of genes in bacteria that are involved in a specific function and are regulated together. The presence or absence of certain environmental factors, like lactose, can turn the operon on or off, controlling the expression of the genes within it.

How can the presence of lactose in the environment affect the expression of the lac operon in bacteria?

When lactose is present in the environment, it can trigger the expression of the lac operon in bacteria, allowing them to break down lactose. This results in the production of acids that lower the pH of the environment, which can be detected using indicators like those in MacConkey Agar.

What is MacConkey Agar and how is it used to differentiate between lac positive and lac negative bacteria?

MacConkey Agar is a type of growth medium used in laboratories to distinguish between bacteria that can and cannot break down lactose. It contains a pH-sensitive indicator that turns pink when the pH drops due to acid production by lac positive bacteria, allowing for easy identification of the bacteria's genotype expression.

Outlines

00:00

🐇 Environmental Influences on Genotype Expression

This paragraph discusses the concept of environmental genotype effects, which is how the environment can influence the expression of an organism's genes. It uses the example of the Himalayan rabbit to illustrate how body temperature can disrupt the expression of genes responsible for melanin production, leading to the characteristic black and white coloration. The paragraph also mentions an experiment involving shaving and cooling the rabbit's back to alter the expression of the melanin gene, demonstrating the direct impact of environmental conditions on genotype expression. The speaker then transitions to discussing how traits can be expressed differently in animals like the arctic fox and hare, and in plants, due to environmental changes.

05:02

🌡 Adaptation and Genotype Expression in Animals and Plants

The second paragraph delves into how animals like the arctic fox and the arctic hare adapt their coloration based on seasonal changes to blend in with their environment, a process influenced by the hormone melatonin secreted by the pineal gland. In winter, increased melatonin production leads to reduced melanin and a white appearance, while in summer, decreased melatonin allows for increased melanin production and a darker color. The paragraph also covers how plants, specifically hydrangeas, can vary their flower color in response to soil pH levels, with lower pH levels resulting in blue flowers due to the uptake of aluminum. Lastly, the paragraph introduces the concept of operons in bacteria and how the presence or absence of the lac operon affects the bacteria's ability to break down lactose, with a brief mention of using MacConkey Agar to differentiate between lac positive and lac negative bacteria based on color changes indicative of pH changes.

Keywords

💡Genotype

Genotype refers to the genetic makeup of an individual, encompassing all the genes inherited from its parents. In the context of the video, genotype is the foundation for an organism's physical traits, which can be influenced by the environment. An example from the script is the Himalayan rabbit, where the genotype for melanin production is expressed differently based on the body temperature, resulting in a distinct coat pattern.

💡Phenotype

Phenotype is the observable physical or biochemical characteristics of an individual, which result from the interaction of its genotype with the environment. The video emphasizes that while the genotype provides the potential for certain traits, the phenotype is what is actually expressed and visible. The script uses the Himalayan rabbit's coat color as a clear example of how the phenotype can differ from the underlying genotype due to environmental factors.

💡Environmental Genotype Effects

Environmental genotype effects describe how environmental conditions can influence the expression of an organism's genotype. The video script explains this concept by showing how the body temperature of the Himalayan rabbit affects the expression of the gene responsible for melanin production, altering the animal's coat color. This illustrates the dynamic relationship between genetics and the environment.

💡Melanin

Melanin is a pigment found in the skin, hair, and feathers of animals, responsible for coloration. In the video, melanin is crucial for the black coloration of the Himalayan rabbit. The script explains how the expression of the gene for melanin is temperature-sensitive, with cooler body parts expressing the gene and producing black fur, while warmer parts do not.

💡Himalayan Rabbit

The Himalayan rabbit is a species used in the video as an example to illustrate environmental genotype effects. The script describes how these rabbits are born black but develop a lighter coat pattern due to the disruption of melanin production in warmer areas of their body. This serves as a clear demonstration of how environmental factors can alter the expression of genetic traits.

💡Pineal Gland

The pineal gland is an endocrine gland in the brain that secretes melatonin, a hormone associated with the regulation of sleep-wake cycles and seasonal functions. In the video, it is mentioned in relation to the arctic fox, which changes its coat color seasonally. The gland's secretion of melatonin affects melanin production, resulting in a white coat in winter and a darker one in summer, demonstrating the influence of environmental light on phenotype.

💡Melatonin

Melatonin is a hormone produced by the pineal gland that plays a role in the regulation of sleep and circadian rhythms. The video script explains how the production of melatonin in arctic foxes is linked to the season, with higher levels in winter leading to less melanin production and a whiter coat, and lower levels in summer leading to a darker coat. This is an example of how hormones can mediate environmental effects on genotype expression.

💡Arctic Fox

The arctic fox is an animal species highlighted in the video for its ability to change coat color with the seasons as a form of camouflage. The script explains that the fox's phenotype is influenced by the secretion of melatonin from the pineal gland, which in turn is affected by the amount of daylight, illustrating the complex interplay between genetics, hormones, and environmental conditions.

💡Hydrangea

Hydrangea is a genus of plants known for the ability of some species to change flower color based on soil pH. The video script uses hydrangeas to demonstrate how environmental factors, specifically soil acidity, can influence the expression of genetic traits, resulting in flowers that can be pink or blue depending on the pH level.

💡pH

pH is a measure of the acidity or alkalinity of a solution. In the context of the video, pH is discussed in relation to how it affects the color of hydrangea flowers. The script explains that a higher pH (alkaline conditions) results in pink flowers, while a lower pH (acidic conditions) leads to blue flowers, showing how environmental chemistry can impact the expression of genetic potential.

💡Operon

An operon is a unit of DNA that includes a set of genes under the control of a single regulatory element in bacteria. The video script discusses the lac operon as an example of how bacteria can regulate the expression of multiple genes in response to environmental conditions, such as the presence of lactose, which can turn the operon on or off.

💡MacConkey Agar

MacConkey Agar is a type of culture medium used in microbiology to differentiate between types of bacteria based on their ability to ferment lactose. The video script explains how bacteria growing on this medium can change its color due to the production of acids when lactose is broken down, which is an indicator of whether the bacteria are lac positive or lac negative, demonstrating the practical application of genotype expression in a laboratory setting.

Highlights

The environment can affect the expression of genotypes, influencing an organism's phenotype.

Genotypes are the genes an organism has, while phenotypes are the physical traits expressed by those genes.

Himalayan rabbits naturally express genes for melanin production, but body warmth disrupts this expression, leading to a non-uniform black color.

An experiment showed that cooling the body core of a Himalayan rabbit allows for uniform melanin production, demonstrating environmental control over gene expression.

The podcast will cover how environmental changes affect the expression of genotypes in animals, plants, and bacteria.

Arctic foxes and hares change their coat color seasonally to adapt to their environment, regulated by the pineal gland and melatonin production.

Plants, such as hydrangeas, can change flower color based on soil pH, showing environmental influence on plant phenotypes.

Bacteria can regulate gene expression through operons, such as the lac operon, in response to environmental conditions.

The lac operon in bacteria allows for the expression of genes necessary for lactose breakdown, with presence indicating 'lac positive' bacteria.

MacConkey Agar is used to differentiate between lac positive and lac negative bacteria based on pH changes and color indicators.

Gene expression in bacteria can be observed through color changes in agar, providing a visual representation of genotype expression.

Environmental genotype effects are crucial for survival and adaptation, as seen in the examples of Himalayan rabbits, arctic foxes, and plants.

The study of environmental effects on genotypes helps us understand the complexity of gene expression and its dependence on external factors.

The transcript provides insights into the interplay between genetics and the environment, highlighting the dynamic nature of biological systems.

Understanding how the environment influences gene expression can have practical applications in areas such as agriculture and medicine.

The transcript emphasizes the importance of studying genotype-environment interactions for a comprehensive understanding of biological processes.

Transcripts

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.