yego.me
💡 Stop wasting time. Read Youtube instead of watch. Download Chrome Extension

Chromosome pairs | Inheritance and variation | Middle school biology | Khan Academy


3m read
·Nov 10, 2024

  • [Instructor] - Hi, everyone. Today, we're gonna talk about chromosome pairs. But first, I've got a question for you. Between a black mulberry plant, a Guinea pig, and a human being, which organism do you think has the most chromosomes?

The mulberry plant has green leaves and delicious berries. The Guinea pigs are adorable, tiny mammals with multiple body systems, and humans have incredibly powerful brains and the ability to form complex social relationships.

Before I tell you the answer, let's learn a little more about chromosomes. Chromosomes are structures that contain an organism's genes. And genes are the units of heredity passed from parent to offspring that affect an organism's traits.

Chromosomes, and the genes they contain, are located inside an organism's cells. In multicellular organisms, the chromosomes are found within the cell's nucleus. Many species have chromosomes that come in matched pairs. For example, here's an image taken with a microscope of chromosomes from a typical human body cell.

The chromosomes are laid out in an organized way, allowing us to see that humans have 46 chromosomes, which can be organized into 23 pairs. Each of these is a pair of chromosomes. This is one chromosome, and this is the second chromosome. These paired chromosomes are called homologous chromosomes.

Homologous chromosomes have the same size and shape. They also contain the same genes in the same locations. Remember, an organism's genes affect its traits. Genes often come in different variations, called alleles. Different alleles of a gene can cause different versions of a trait.

In an organism, a pair of homologous chromosomes may have the same allele for a gene, or they may have different alleles for a gene. To help us understand this, let's take a look at an illustrative example using pea plants. Pea plants can have pink or purple flowers. These colors are determined by two different variations, or alleles, of a single flower color gene.

Pea plants have a copy of this flower color gene on each of two chromosomes in a homologous pair. A single pea plant may have two copies of the pink allele, two copies of the purple allele, or one copy of each. The color of flowers that the pea plants end up with depends on how the alleles interact. But we'll cover that in another video.

An image like this one, of an individual's chromosomes, lined up in an organized way, is called a karyotype. Scientists and medical professionals can examine an individual's karyotype under the microscope to see if they might have a genetic condition. This could show up as size differences between chromosomes within each homologous pair or the presence of an extra chromosome.

Now that you're a little more familiar with chromosomes, let's return to the question I asked at the beginning of this video. Between black mulberry plants, Guinea pigs, and humans, which organism has the most chromosomes? Any guesses?

The black mulberry plants do! These plants have a whopping 308 chromosomes. Guinea pigs come in second with 64 chromosomes. And like we said earlier, us humans only have 46 chromosomes. So we come in third. Are you surprised?

Believe it or not, humans, with their big brains and complex social structures, actually have far fewer chromosomes than many seemingly less complex organisms. Are black mulberry plants more complicated than we perceive? Perhaps. And perhaps there is more to understanding the role chromosomes play in determining traits.

That's it for today, thanks for watching.

More Articles

View All
How To Get A PERFECT Credit Score For $0
What’s up, guys? It’s Graham here. So for the last 12 years, I have studied, researched, and analyzed every single aspect of building your credit score to the point where eventually I could brag on YouTube about achieving an 800, which is the threshold th…
Peter Reinhardt on Finding Product Market Fit at Segment
The average person probably doesn’t know what Segment is. Mm-hmm. So could you explain? For sure. So Segment helps companies give their customers a better customer experience, and we do that by helping them organize all of their internal data about all t…
Ideas, Products, Teams, and Execution with Dustin Moskovitz (How to Start a Startup 2014: Lecture 1)
Welcome! Can I turn this on? Baby, all right. Hit people here. Can you guys hear me? Is the mic on? No? Maybe you can ask them to turn it on. Maybe we can get a big—there we go. All right! Maybe we can get a bigger auditorium; we’ll see. So welcome to CS…
THE END OF $0 REAL ESTATE | Major Changes Explained
What’s up, grandma’s guys? Here. So, a few days ago, I made a video discussing my thoughts on the new personal tax increases along with an analysis of how that would affect the stock market. However, I purposely left out one crucial point, which has the …
3 Sources of Water on the Moon
Is there water on the Moon? The obvious answer seems to be no. Because during a day on the Moon, which lasts 2 Earth weeks, the temperature on the lunar surface gets up to 123 degrees Celsius, which would be enough to boil away any water if the Moon had a…
Solar Eclipse 101 | National Geographic
[Narrator] A solar eclipse happens when a new moon moves between the Earth and the sun, blocking some or all of the sun’s rays from reaching the Earth. By cosmic chance, even though the sun is 400 times wider than the moon, it’s also 400 times farther awa…