Eukaroyte Genetics

As you are reading this sentence, you’re probably saying to yourself, “what the heck does eukaroyte, (you-carry-out), means?” If you take any genetics course, then it’s almost certain that you’ll come across many terms that you may or may not understand. In short, the term eukarotye refers to all the complex living organisms that live on the planet Earth.

Oh yeah!! Things are going to get harder, so read things twice.

Of course there would be a “prokaroyte (pro-carry-out)” for every “eukaroyte“. For every “intron“, you’d have an “exon“. And for every potato, you’d have a tomato. (How’s my humor?)

But seriously, in this section of Genetics R Us you are going to be introduced to a whole new list of new terms. These terms: prokaroyte, eukaroyte, inton, and exon all have to do with the genetics of eukaroyte organisms of which we are about to learn. As you read this section of Genetics R Us, its important to keep in mind two things.

First, I have to admit that things are going to get bit harder and detailed. More so, things are going to get really detailed. So it’s important that if you don’t understand to read over the material more than once.

Second, from here on out, Genetics R Us will many deal with the genetics of eukaryote organisms. In later concepts such as replication, mutation, etc, Genetics R Us will speak from the perspective of eukaroytes. Yeah, you guessed it!! Things are going to get a little tough, but hang in there, I’ll make it as easy as possible. With these two points in mind, let’s begin.

What’s a Prokaroyte?

The first thing that you’re probably wondering is what the heck is a prokaroyte. Simply put, the word, “prokaroyte”, refers to all “simple” life forms that current live on the planet Earth. By simple, we mean primitive, single-cell organisms. If you’ve ever heard of bacteria, then you already know what a prokaroye is!!

Shown toward right is photograph of a bacteria known as Vibrio cholerae. (To make things easier, just simply say the cholera bacteria) This bacteria causes a disease in humans called cholera.

An example of a prokaroyte shown through the eyes of an electron microscope.

Prokaroytes are all over the place. From bacteria to the newly distinguished Archaea, (another class of prokarotyes), prokarotyes have filled every enviromental niche that you can imagine. Believe it, prokaroytes are all over the place. This includes the hot springs under the oceans, to the your pits of your stomach and even inside your mouth. Let’s now see what makes a prokaryote, a prokaroyte!!!!!

If you remember from the first part of Genetics R Us, every living thing on the planet, (for example people, mice, plants, bacteria), are composed of cells. Your skin is made up of skin cells. Your bones are made of bone cells, etc. I’m sure by now, you get the point.

Well, prokaroytes are no different. They are made of cells, or should I say, they are made up of a single cell. Let’s see!

Here’s a prokaryotic cell. Notice that there is no nucleus. The DNA is contained within a fluid called cytoplasm, which is inside the cell membrane. Also, there is a tail structure known as the flagellum which a prokaroytes uses to move in different directions.

A basic prokaroyte cell known as E-coli. Notice that there is no nucleus.

This is about as simple as you can get. The most important characteristic is the fact a prokaryotic cell has NO NUCLEUS. This is why we call prokaroytes simple life forms. They are also the oldest life forms. Going back almost 3.8 billion years, prokarotyes were the first life forms to appear. There are fossils of these creatures in rocks that are as old as the Earth. Now let’s take a look at their descendants, the eukarotyes!!

You’re a Eukaroyte!!

Believe it or not, you, the reader of this webpage, are a eukaroyte. Humans are very complex eukaroytes, but a eukaroyte nonetheless. In this part, we are going to take a look at the famous eukaroytes. So let’s not beat around the bush any longer, let’s get to it!!!!!

Simply put, eukaroytes are the “complex” living organisms that currently live on the Earth. This includes all life forms which are not bacteria and archea. This would include worms, flies, yeast, ameboas, plants, and us.

Shown toward your right are some of the most popular eukaroytes.

The most important point to understand is that eukaroytes are nothing more than prokaroytes with some extra added features. Having been around for over 1.5 billion years, eukaroytes are the straight descendants of prokaroytes. We know this because eukaroytes have features that are clearly prokaroytes in origin. Having said that, let’s see what makes a eukaryote, a eukaroyte!!!!

Shown toward your left is a eukaroytic plant cell. The most important feature of a eukaroyte is the presence of a nucleus. Other features include a mitochondria, chloroplast, cell wall, cytoplasms, etc. Notice both mitochondria and chloroplast are in fact prokaroytes themselves.

This is how its known that eukaroytes are descendants of prokaroytes. Eukaroytes are referred to as being complex because of the number of organelles, (mitochondria, chloroplasts, ribosomes,nucleus, etc) that they contain. Now that you have a basic understanding of prokaroytes and eukaroytes we can finally move on and learn the genetics of both.

What’s the Point?

At this point, you’re probably saying to yourself, “What was the point of all that talk about prokaroytes and eukaroytes. I thought this was a genetics course.” Well, this is a genetics course, and now we’re ready to rumble. The basic facts about prokaroytes and eukaroytes was required so you can grasp the concepts which we are about to learn. Let’s begin with the genetics of prokaroytes.

If you remember a gene is a piece of DNA that contains instructions to create a protein. Your cells basically “read” genes so they know which and what type of protein to make. Shown toward your left is a model of this!!!

Now shown toward your left is a basic prokaryote cell and its all important gene. Now look at the structure of the gene. As shown before a gene has three basic parts: a promoter, RNA encoding sequence, and a terminator.

Here’s a quick review of what these three parts are.

A promoter is a repeating sequence of bases that is used by a cell to begin reading. This tells a cell where to begin “reading”.
A terminator is the portion of the gene that tells the cell where and when to stop reading the gene. Without a terminator, a cell would continue reading.
The RNA-coding sequence is the DNA that has the actual instruction for making a protein. From this section of DNA, RNA is made, and then from that RNA, the protein is generated.

This bit of information is nothing new to you. We have studied genes in earlier parts of Genetics R Us. Now lets get to the hard part, the genetics of eukaroyte organisms. Remember, if you have questions then read things twice. Let’s begin!!!!

The Hard Part!!

The key to understanding the genetics of eukaryotes is that eukaryotes have everything that prokaryotes have and more. Let’s take a look!!!!

If you remember your genome is the entire six feet of DNA that is contained within a sperm or egg cell. This six feet of DNA contains the entire set of instructions that is used by your cells to build and construct a single human being.

Now your genome has a set number of genes on it. The areas of DNA that are not genes are called non-coding DNA segments. These non-coding segments ARE NOT READ BY YOUR CELLS. In other words, no RNA or protein, are made from these parts. Now here’s the important part. These non-coding parts lay OUTSIDE of your genes. You can see this in the model shown toward your left.

Now here’s the part that you have to grasp. These non-coding DNA segments can also lay INSIDE of a gene. In this situation, these non-coding DNA segments are then to referred to as INTRONS. Introns are present only inside the genes of eukaroytes, not prokaryotes. The parts of a eukaroyte gene that are read by a cell are called EXONS. Now let’s take a look at a eukaroyte gene.

Here’s a basic eukaroyte gene. It has a promoter, terminator, and an RNA coding sequence. The RNA coding sequence has both introns and exons that make it up.

The most important part of a gene is the RNA-coding DNA sequence. This is the part of the gene that is “read” by your cells to first make: RNA, and then from that RNA, make a protein. However, introns (which don’t get “read”), lay within the RNA-coding DNA sequence. So, we have a problem!! Here’s the solution.

What happens is that the introns are partially read by your cells. In other words, RNA is made from the intron, but a protein is not. Shown toward your left is a model of this happening!!!

So what this means is that the RNA strand, (once it gets made), has both introns and exons within it. The final step is the formation of the protein from the RNA, however something very important happens. Let’s see what happens!!!

If you remember introns are non-coding DNA or RNA segments. No protein is made from a intron. Therefore the RNA introns must be removed. A special protein called a splicesome removes the RNA intron.

After the introns are removed from the RNA strand, the new RNA strand contains only exons within it. It is therefore shorter than the old RNA strand which had introns within it. From there, the cell will make a protein and use it.

However, before the protein is made two more major events take place. Here’s is what happens!

At both ends of exon based RNA strand is he addition of the cap and poly(A) tail. The cap is a stretch of three modified nucleotides which is attached to the 5′ end of the pre-mRNA. The poly(A) tail is a stretch of adenine nucleotides which is attached to the 3′ end of the pre-mRNA.

And there you have it, the genetics of eukaryote organisms. You’re probably thinking that this was a lot of information. Well, it was a lot of information, so it very important that if you don’t understand to go over this section of Genetics R Us twice and review what you have just learned. If you like, I have provided below a nice link to a quick review of the material in this section of Genetics R Us. Check it out!!!!

Here’s a link to a quick review of what we have just learned!!