Phenotype plasticity | Heredity | AP Biology | Khan Academy

Summary

The video script discusses the concept of genotype and phenotype through the example of NASA astronauts and identical twins, Mark and Scott Kelly. It explains that despite sharing the same genetic information (genotype), observable characteristics (phenotype) can vary due to environmental influences, a phenomenon known as phenotype plasticity. The script highlights a study where Scott's year-long stay in space resulted in a 7% gene expression difference, illustrating the impact of the space environment on his phenotype, which differed from his twin brother's.

Takeaways

• 🌌 The script discusses two NASA astronauts, Mark and Scott Kelly, who are identical twins.
• 🧬 Genotype refers to the genetic information encoded in an organism's genes, which includes DNA sequences on chromosomes.
• 👤 Phenotype is the observable characteristics of an organism, which can vary even among individuals with the same genotype.
• 🌿 The environment plays a significant role in affecting an individual's phenotype, beyond the influence of their genes.
• 👬 Identical twins Mark and Scott Kelly have the same genotype, but their phenotypes are not identical due to environmental factors.
• 🚀 NASA conducted an experiment to study the effects of space travel on gene expression, focusing on Scott Kelly's extended stay in space.
• 🔍 Before and after Scott's space mission, scientists compared his body's expression of certain characteristics to his twin brother's.
• 🌌 Differences in mitochondria and gene expression were observed in Scott after his time in space, highlighting the impact of the space environment.
• 🔢 A significant 7% difference in gene expression was noted in Scott compared to his twin, demonstrating the extent of phenotype plasticity.
• 🌐 The space environment, characterized by low oxygen and high carbon dioxide levels, was theorized to have influenced Scott's gene expression and phenotype.
• 🧪 The study of the Kelly twins provides insights into how identical genotypes can result in different phenotypes due to environmental influences.

Q & A

Who are the two individuals in the picture mentioned in the script?

The two individuals in the picture are Mark Kelly and Scott Kelly, both NASA astronauts and identical twins.

What is the main focus of the script regarding Mark and Scott Kelly?

The script focuses on the concepts of genotype and phenotype, using Mark and Scott Kelly as examples to illustrate how environmental factors can influence phenotype despite identical genotypes.

What does the term 'genotype' refer to in the context of the script?

Genotype refers to the actual genetic information encoded in an organism's genes, which includes the DNA sequences on chromosomes that code for various proteins and characteristics.

What is meant by 'phenotype' as discussed in the script?

Phenotype refers to the observable characteristics of an organism, which can be influenced by both genetic information (genotype) and environmental factors.

Why might two people with the same genotype not have identical phenotypes?

Two people with the same genotype might not have identical phenotypes because environmental factors can influence how genes are expressed, leading to variations in phenotype.

What is the concept of 'phenotype plasticity' explained in the script?

Phenotype plasticity is the idea that the same genotype can result in variations of phenotype due to different environmental influences on gene expression.

What experiment did NASA conduct involving Scott Kelly to study phenotype plasticity?

NASA conducted an experiment where Scott Kelly spent an extended period in space while his twin brother, Mark, did not, to observe the effects of the space environment on gene expression and phenotype.

What were some of the differences found in Scott Kelly's body after his extended stay in space?

After Scott Kelly's extended stay in space, differences were found in his mitochondria and in the expression of certain genes, with a 7% difference in gene expression compared to before his space mission.

What environmental factors in space might have contributed to the changes in Scott Kelly's phenotype?

The environmental factors in space that might have contributed to the changes in Scott Kelly's phenotype include a low oxygen environment, high levels of carbon dioxide, and stressors associated with space travel.

How did the space environment affect the expression of Scott Kelly's genes, according to the script?

The space environment affected the expression of Scott Kelly's genes by causing changes in mitochondria and gene expression, resulting in a 7% difference in gene expression and demonstrating phenotype plasticity.

What does the comparison between Mark and Scott Kelly demonstrate about the influence of environment on phenotype?

The comparison between Mark and Scott Kelly demonstrates that even with the same genetic information (identical genotype), environmental factors can lead to differences in how genes are expressed, affecting the observable characteristics (phenotype) of an individual.

Outlines

00:00

🚀 Phenotype Plasticity in Identical Twins

The video introduces NASA astronauts Mark and Scott Kelly, identical twins, to explore the concepts of genotype and phenotype. Genotype refers to the genetic information encoded in an organism's DNA, while phenotype is the observable characteristics expressed by an organism. The video highlights that even with the same genotype, environmental factors can lead to variations in phenotype, a concept known as phenotype plasticity. The Kelly twins serve as an example of this, with Scott's extended stay in space resulting in a 7% difference in gene expression compared to his brother, illustrating the impact of the space environment on phenotype.

Keywords

💡Genotype

Genotype refers to the complete set of genetic information encoded in an organism's DNA. It is the blueprint of an individual's inherited traits. In the video, the concept is used to illustrate that Mark and Scott Kelly, being identical twins, share the same genotype, which is the basis for understanding how environmental factors can influence phenotype despite identical genetic makeup.

💡Phenotype

Phenotype is the observable characteristics of an organism, such as its physical appearance, behavior, and biochemical properties. It is the result of the interaction between an individual's genotype and the environment. The video uses the example of the Kelly twins to show that even with the same genotype, environmental influences can lead to differences in phenotype, such as facial characteristics.

💡Identical Twins

Identical twins are siblings that develop from the same zygote and, therefore, have the same genetic material. In the context of the video, Mark and Scott Kelly are highlighted as identical twins to emphasize that despite having identical genotypes, their phenotypes can vary due to environmental factors, a concept central to the video's theme.

💡Chromosomes

Chromosomes are thread-like structures composed of DNA and proteins, found in the nucleus of cells, and they carry genetic information. The script explains that genotype is found within the DNA of chromosomes, where sections of DNA code for various traits, contributing to an organism's phenotype.

💡DNA

DNA, or deoxyribonucleic acid, is the molecule that carries the genetic instructions for the development, functioning, growth, and reproduction of all known living organisms. The video script describes DNA as the carrier of genetic information on chromosomes, which codes for proteins and other functions that determine an organism's traits.

💡Proteins

Proteins are large biomolecules composed of amino acids and are essential for the structure, function, and regulation of an organism's cells, tissues, and organs. In the script, proteins are mentioned as the products of gene expression, which are coded by sections of DNA and contribute to an organism's phenotype.

💡Phenotype Plasticity

Phenotype plasticity is the ability of an organism to change its phenotype in response to changes in the environment. The video uses the term to describe how Scott Kelly's phenotype changed after spending an extended period in space, illustrating the concept that the same genotype can result in different phenotypes under varying environmental conditions.

💡Gene Expression

Gene expression is the process by which the information encoded in a gene is used to produce a functional product, usually a protein. The video discusses how gene expression in Scott Kelly changed after his time in space, resulting in a 7% difference in gene expression compared to his twin brother who remained on Earth.

💡Mitochondria

Mitochondria are organelles found in the cells of eukaryotic organisms, known as the 'powerhouses' of the cell because they generate most of the cell's supply of adenosine triphosphate (ATP), used as a source of chemical energy. The script mentions differences in mitochondria as one of the changes observed in Scott Kelly's body after his time in space.

💡Space Environment

The space environment refers to the conditions outside Earth's atmosphere, characterized by factors such as microgravity, radiation, and a unique atmosphere. In the video, the space environment is presented as a significant environmental factor that contributed to the changes in Scott Kelly's phenotype, highlighting the impact of space travel on human biology.

💡NASA

NASA, the National Aeronautics and Space Administration, is the United States government agency responsible for the nation's civilian space program and for aeronautics and aerospace research. The video script mentions NASA in the context of the study on the Kelly twins, emphasizing the agency's role in conducting research on the effects of space travel on human genetics and phenotype.

Highlights

Introduction of identical twin NASA astronauts, Mark and Scott Kelly.

Discussion on genotype and phenotype and their differences.

Explanation of genotype as the genetic information encoded in an organism's genes.

Description of chromosomes and DNA as carriers of genetic information.

Differentiation between genotype and phenotype in terms of observable characteristics.

The influence of environment on phenotype, even among individuals with the same genotype.

Observation that identical twins Mark and Scott Kelly have different facial characteristics.

Introduction of the concept of phenotype plasticity.

The idea that phenotype plasticity can result from the same genotype.

NASA's experiment on phenotype plasticity by comparing Scott Kelly's gene expression in space.

Pre-space mission comparison of gene expression in Scott and Mark Kelly.

Post-space mission differences in Scott Kelly's gene expression.

A 7% difference in gene expression observed in Scott Kelly after extended time in space.

The impact of the space environment on Scott Kelly's phenotype.

Theoretical contributions on how low oxygen and high carbon dioxide levels in space affect gene expression.

The role of stressors from space travel in altering gene expression.

The potential implications of these findings on understanding the interaction between genotype and environment.

Transcripts

- [Instructor] The folks you see in this picture

are two NASA astronauts

who also happen to be identical twins.

On the left here, this is Mark Kelly,

you can see his name on his patch right over there,

and then this is Scott Kelly.

And the reason why we want to look

at these two astronauts in particular

is to think about genotype and phenotype

that we have been introduced to in other videos.

So just as a bit of a review,

when people talk about genotype,

they're talking about the actual genetic information

encoded in an organism's genes.

So, if you go inside a cell we have chromosomes

and then on those chromosomes, there are long,

each chromosome's a long stretch of DNA.

And then sections of that long stretch of DNA

will code for various things,

often usually various proteins.

But there's a difference between what is actually,

what information is in one's genes

versus what actually gets expressed.

The observable characteristics, that is phenotype,

and two people with the same genotype

they might have a very similar phenotype

but they won't necessarily have an identical phenotype

because above and beyond the genes affecting phenotype,

you also have the environment

affecting someone's phenotype.

So, as you can see here, Mark and Scott Kelly,

they're identical twins,

they have the same genotype.

But if you just look at their facial characteristics

you can see that you could tell

the difference between the two,

and it's not just the fact that Mark has a mustache

and that Scott doesn't, we could draw in a mustache,

we would still see that they look different.

And that's because their bodies developed in different ways

based off the environment that they happen to be in.

And this idea that the same genotype

could result in variations of phenotype,

this is known as phenotype plasticity.

Phenotype.

Phenotype plasticity.

And maybe in one of the most extreme experiments

ever conducted on phenotype plasticity,

NASA was intrigued to see,

well, what would happen to the gene expression

if Scott Kelly spent an extensive period of time in space

while his twin brother didn't.

So they looked at how their bodies expressed

certain characteristics before Scott spent

an extended period of time in space.

And then after he spent that time in space

they studied his body

and they saw that there was differences in the mitochondria,

differences in which genes were expressed.

In fact, there was a 7% difference in the gene expression

after the extended time in space for Scott.

So that's the example of that space environment

changing Scott's phenotype.

And the NASA scientists theorized

that it was a low oxygen environment

there was a lot of carbon dioxide in that environment,

there were stressors from space travel

that would have affected how the genotype

which is identical to his brother, Mark's genotype,

how it might have been expressed

resulting in the phenotype plasticity

above and beyond what other changes in phenotype

between Scott and Mark accumulated

over the course of their lives

despite having the same genetic information.