The genes you don't get from your parents (but can't live without) - Devin Shuman

Summary

The script delves into the unique nature of mitochondria, our cells' second genome, which originated from an ancient symbiotic event. Mitochondria, essential for converting food and oxygen into ATP, possess their own DNA and vary significantly across species. In humans, mitochondrial DNA is maternally inherited and undergoes a dynamic replication process, affecting cellular health. Understanding mitochondria's evolution and function can offer insights into both our health and evolutionary history.

Takeaways

• 🧬 Mitochondria contain a distinct set of genes separate from the chromosomes inherited from our parents.
• 🌏 This secondary genome is found in all animals, plants, fungi, and most multicellular organisms on Earth.
• 🕵️‍♂️ Mitochondria are thought to have originated from a single-celled organism engulfing its ancestor about 1.5 billion years ago.
• 🔋 They are crucial for converting food and oxygen into ATP, the energy currency of the cell.
• 🩸 Mature red blood cells are an exception, lacking mitochondria to ensure oxygen delivery efficiency.
• 🧬 Mitochondrial DNA varies significantly across species, with mammals typically having 37 genes, plants like cucumbers up to 65, and some fungi only 1.
• 🧬 Mitochondria possess their own DNA, which is subject to evolution, both alongside and separate from their host organisms.
• 👶 Mitochondrial DNA is maternally inherited, with the sperm's mitochondria dissolving after conception.
• 🧬 The number of mitochondrial DNA copies inherited from our mothers can exceed 150,000, each with potential slight variations.
• 🧬 Mitochondrial DNA distribution within the body is random and can change throughout life due to the independent replication process of mitochondria.
• 🔬 Mitochondria are dynamic entities that, while influenced by their environment, also require instructions from our nuclear DNA for replication and regulation.

Q & A

What is the significance of mitochondria in our cells?

Mitochondria are organelles within our cells that play a crucial role in converting energy from food and oxygen into ATP, a molecule that our cells can use for energy. Without this energy conversion, our cells would begin to die.

How are mitochondria different from other parts of our body?

Mitochondria contain their own DNA, separate from the nuclear DNA inherited from our parents, and they have a unique evolutionary history, believed to have originated from an ancient engulfed single-celled organism.

Why do mitochondria have their own DNA?

Mitochondria are thought to have evolved from a symbiotic relationship with an ancient single-celled organism, which has resulted in them retaining their own distinct genetic material.

How does the number of genes in mitochondria vary across different organisms?

The number of genes in mitochondria can vary significantly. For example, in mammals, there are usually 37 genes, while in plants like cucumbers, there can be up to 65, and some fungal mitochondria may have only 1 gene.

Why don't mature red blood cells contain mitochondria?

Mature red blood cells do not contain mitochondria because their primary function is to transport oxygen, and having mitochondria would consume oxygen before it could be delivered to other parts of the body.

How is mitochondrial DNA inherited?

In almost all species, mitochondrial DNA is inherited solely from the mother. The sperm's mitochondria, which are present in small numbers, dissolve after conception, and the egg contributes thousands of mitochondria with multiple copies of mitochondrial DNA.

How does the distribution of mitochondrial DNA vary within an individual?

The mitochondrial DNA inherited from the mother is distributed randomly throughout the body's cells as the fertilized egg divides and differentiates into tissues and organs.

What is the replication process of mitochondria in relation to our cells?

Mitochondria have a separate replication process from the cells they inhabit. As cells divide, mitochondria are distributed to new cells, and they also undergo fusion and division on their own timeline.

How do mitochondria maintain their function and genetic integrity?

Mitochondria can sequester faulty DNA or non-functional mitochondria for removal, ensuring that they maintain their ability to produce energy and preserve their genetic integrity.

What role do mitochondria play in our evolution and health?

Mitochondria are still evolving and can influence our health by affecting cellular energy production. Understanding their function and evolution can provide insights into human health and our evolutionary history.

How do mitochondria interact with the nuclear DNA of the cell?

Although mitochondria have their own genome and replicate separately, they rely on instructions from the host cell's nuclear DNA to function properly. Additionally, genes involved in building and regulating mitochondria come from both parents.

Outlines

00:00

🧬 Mitochondrial DNA: Our Cellular Companions

The script introduces the concept of a secondary genome within our cells, the mitochondria, which are distinct from the chromosomes inherited from our parents. Mitochondria are organelles with their own DNA and are thought to have originated from a single-celled organism that was engulfed by another about 1.5 billion years ago. They are crucial for converting food and oxygen into ATP, the energy currency of cells. While humans have over 200 types of cells, only mature red blood cells lack mitochondria due to their oxygen transport function. Mitochondrial DNA varies significantly across species, with mammals typically having 37 genes, plants like cucumbers up to 65, and some fungi only 1. There is ongoing evolution and variation in mitochondrial DNA, which is passed down maternally in most species, with sperm mitochondria dissolving post-conception. The egg, however, contains thousands of mitochondria with over 150,000 copies of mitochondrial DNA, each potentially unique.

Keywords

💡Mitochondria

Mitochondria are organelles found in the cells of eukaryotic organisms. They are often referred to as the 'powerhouses of the cell' because they generate most of the cell's supply of adenosine triphosphate (ATP), which is used as a source of chemical energy. In the video, mitochondria are highlighted as having their own distinct genome separate from the nuclear DNA inherited from parents, playing a crucial role in cellular energy production and evolution.

💡Genome

A genome refers to the complete set of genetic information in an organism. The video script discusses the unique aspect of mitochondria having their own genome, separate from the nuclear genome, which is a key concept in understanding the evolutionary and functional differences between mitochondria and the rest of the cell.

💡Chromosomes

Chromosomes are thread-like structures consisting of DNA and protein, found in the nucleus of animal and plant cells. They carry genetic information in the form of genes. The script mentions the 23 pairs of chromosomes inherited from parents, contrasting them with the separate mitochondrial DNA.

💡ATP (Adenosine Triphosphate)

ATP is the primary energy currency of the cell, used to power various cellular processes. The script explains that mitochondria are essential for converting food and oxygen into ATP, illustrating their fundamental role in cellular energy metabolism.

💡Evolution

Evolution is the process by which species of organisms arise and develop through genetic variation and natural selection. The video discusses the evolutionary history of mitochondria, suggesting that they originated from an ancestral single-celled organism that was engulfed by another, leading to the symbiotic relationship that exists today.

💡Mitochondrial DNA

Mitochondrial DNA (mtDNA) is the DNA located in mitochondria and is inherited maternally in most species. The script points out that mtDNA varies more across species than nuclear DNA and that it is passed down from only one parent, the mother, in humans and most animals.

💡Multicellular Organisms

Multicellular organisms are life forms composed of multiple cells that work together to perform complex functions. The script suggests that the engulfment of mitochondria's ancestor by a single-celled organism approximately 1.5 billion years ago was a pivotal event in the creation of all multicellular organisms.

💡Red Blood Cells

Red blood cells, or erythrocytes, are the most common type of blood cell and are responsible for transporting oxygen from the lungs to the body's tissues. The script notes that mature red blood cells lack mitochondria, as their function of transporting oxygen would conflict with the mitochondria's use of oxygen for energy production.

💡Gene Transfer

Gene transfer refers to the movement of genes from one organism to another, often through mechanisms like horizontal gene transfer. The video script implies that some of the genes from the mitochondria's ancestors were transferred to the host's genome, which is a significant aspect of the co-evolution of mitochondria and their host organisms.

💡Replication

Replication in the context of the video refers to the process by which genetic material is copied. The script explains that mitochondria have a separate replication process from the cell, which contributes to the variability of mitochondrial DNA within an organism and its dynamic nature.

💡Inheritance

Inheritance in biology refers to the passing on of genetic information from parents to offspring. The script discusses the inheritance of mitochondrial DNA, which is unique in that it is almost exclusively inherited from the mother, highlighting a key aspect of genetic transmission.

Highlights

Mitochondria possess a unique genome separate from the 23 pairs of chromosomes inherited from parents.

Mitochondria's distinct genome is common in every animal, plant, and fungus, and nearly every multicellular organism.

Mitochondria are organelles within our cells with a dual nature, not fully part of us but not separate either.

Around 1.5 billion years ago, mitochondria's ancestors were engulfed by a single-celled organism, leading to multicellular life.

Mitochondria's crucial role is to convert food and oxygen into ATP, the energy currency of cells.

Except for mature red blood cells, all human cells contain mitochondria due to their oxygen transport function.

Mitochondrial DNA varies significantly across species, with mammals having 37 genes, plants like cucumbers up to 65, and some fungi only 1.

Some microbes in oxygen-poor environments are losing mitochondria, with oxymonad monocercomonoides already devoid of them.

Mitochondria are still evolving, both with and independently from the organisms they inhabit.

Mitochondrial DNA is inherited solely from the mother in almost all species, including humans.

The egg contains thousands of mitochondria with over 150,000 copies of mitochondrial DNA.

Mitochondrial DNA variations are scattered randomly throughout the body as the embryo develops.

Mitochondria have a separate replication process from cells, leading to a dynamic and independent existence.

Mitochondria can sequester and remove faulty DNA or non-functional mitochondria during replication.

The inherited mitochondrial DNA can change throughout an individual's life due to its dynamic nature.

Mitochondria are shaped by their environment, which is us, and have genes transferred to the host's genome long ago.

Although mitochondria have their own genome, they rely on instructions from our DNA for replication.

Learning about mitochondria can provide tools for protecting human health and understanding our evolutionary history.

Transcripts

Inside our cells, each of us has a second set of genes

completely separate from the 23 pairs of chromosomes

we inherit from our parents.

And this isn’t just the case for humans—

it’s true of every animal, plant, and fungus,

and nearly every multicellular organism on Earth.

This second genome belongs to our mitochondria,

an organelle inside our cells.

They’re not fully a part of us, but they’re not separate either—

so why are they so different from anything else in our bodies?

Approximately 1.5 billion years ago,

scientists think a single-celled organism engulfed the mitochondria’s ancestor,

creating the predecessor of all multicellular organisms.

Mitochondria play an essential role:

they convert energy from the food we eat and oxygen we breathe

into a form of energy our cells can use, which is a molecule called ATP.

Without this energy, our cells start to die.

Humans have over 200 types of cells,

and all except mature red blood cells have mitochondria.

That’s because a red blood cell’s job is to transport oxygen,

which mitochondria would use up before it could reach its destination.

So all mitochondria use oxygen and metabolites to create energy

and have their own DNA,

but mitochondrial DNA varies more across species than other DNA.

In mammals, mitochondria usually have 37 genes.

In some plants, like cucumbers, mitochondria have up to 65 genes,

and some fungal mitochondria have only 1.

A few microbes that live in oxygen-poor environments

seem to be on the way to losing their mitochondria entirely,

and one group, oxymonad monocercomonoides, already has.

This variety exists because mitochondria are still evolving,

both in tandem with the organisms that contain them,

and separately, on their own timeline.

To understand how that’s possible,

it helps to take a closer look at what the mitochondria inside us are doing,

starting from the moment we’re conceived.

In almost all species, mitochondrial DNA is passed down from only one parent.

In humans and most animals, that parent is the mother.

Sperm contain approximately 50 to 75 mitochondria in the tail,

to help them swim.

These dissolve with the tail after conception.

Meanwhile, an egg contains thousands of mitochondria,

each containing multiple copies of the mitochondrial DNA.

This translates to over 150,000 copies of mitochondrial DNA

that we inherit from our mothers,

each of which is independent and could vary slightly from the others.

As a fertilized egg grows and divides,

those thousands of mitochondria are divvied up into the cells

of the developing embryo.

By the time we have differentiated tissues and organs,

variations in the mitochondrial DNA are scattered at random throughout our bodies.

To make matters even more complex,

mitochondria have a separate replication process from our cells.

So as our cells replicate by dividing, mitochondria end up in new cells,

and all the while they’re fusing and dividing themselves,

on their own timeline.

As mitochondria combine and separate,

they sequester faulty DNA or mitochondria that aren’t working properly for removal.

All this means that the random selection of your mother’s mitochondrial DNA

you inherit at birth

can change throughout your life and throughout your body.

So mitochondria are dynamic and, to a degree, independent,

but they’re also shaped by their environments: us.

We think that long ago,

some of their genes were transferred to their host’s genomes.

So today, although mitochondria have their own genome

and replicate separately from the cells that contain them,

they can't do this without instruction from our DNA.

And though mitochondrial DNA is inherited from one parent,

the genes involved in building and regulating the mitochondria

come from both.

Mitochondria continue to defy tidy classification.

Their story is still unfolding inside of each of our cells,

simultaneously separate and inseparable from our own.

Learning more about them can both give us tools

to protect human health in the future, and teach us more about our history.