Genes

A gene is a molecular unit of heredity of a living organism. A gene is the basic instruction, a sequence of nucleic acids, so a gene is going to be the instruction, it’s going to be the sequence of nucleic acids that tells the cell to code for a certain protein or a certain RNA chain.

It isn’t just one little thing; it’s a sequence that gives an instruction to the cell, while an allele, codes for one variant of that gene.

Mini-test: GENES 

Question 1: The process by which a DNA sequence is copied into a sequence of mRNA is called
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Question 2: A DNA strand with the sequence ACTGAACG is transcribed. What does the sequence of mRNA look like?
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The next lesson: Genetic vs. Environmental Traits, both lessons are included in Practice Tests.

The following transcript is provided for your convenience.

If you’ve heard someone say, oh, she has really good hair genes, or she’s got the gene for blue eyes, that’s not exactly true because everyone has a gene for eye color hair color. For every other trait that you have, but what determines what color your hair is or what color your eyes are, is going to be the alleles for that gene.

There are dominant alleles and recessive alleles, and if you have even one dominant allele, then you’re going to have the dominant gene. If you have two recessive alleles, then you will have that recessive gene. For instance, if you have two parents that have brown eyes, you could still end up with blue eyes, because blue is the recessive gene. Both of your parents had one dominant and one recessive brown and blue eye color allele, the brown would be prevalent in both of them. But since they both have that recessive blue alleles present, you could still end up with blue eyes, because of the recessive alleles combined.

I know that all sounds a little confusing, but it’s just to tell you that each gene, doesn’t determine something all on its own, it’s the alleles that are the variants of that gene that determine what the outcome of each gene sequence is. Genes do specify all proteins and functional chains, so they specify how these are going to be created as functional RNA chains.

Genes hold the information you need to build and maintain an organism cells and pass genetic traits to offspring. Where I was talking about two parents that could have brown eyes and still pass on the blue eye color, it’s because of the alleles that they carry, whether dominant or recessive. Whether you can see it as a physical trait or not, your parents carried genetic traits and they pass this on to you. Some of your physical traits may not all be the same as one or both of your parents, but the genetic traits that you got, did come from the alleles that they had combined and mixed together. You took some of your mother’s alleles or some of your father’s alleles and one of those combined, you ended up with different alleles and different genetic traits of your own, but they both came from the genetic traits your parents have.

Some examples are eye color, a number of limbs and blood type. Some genes you can see right away manifested, such as eye color number of limbs, but blood type is something that you would have to do a little more scientific research to discover. You can also search for certain markers in your body for diseases such as Alzheimer’s or other hereditary diseases. Those can be tested for in your DNA will show, your genes will show, if you have a likelihood of getting that disease and so that’s definitely not something you can see by just looking at someone, it’s something you would have to do more research into. But it’s possible, by looking at the genes in your body.

Now for a gene to create or code for its protein, it must go through transcription and transcription is where single stranded messenger RNA or MRNA is created, that is complementary to the DNA from which it was transcribed and we’ll look at that over here in just a minute. But basically you’re starting with DNA and you’re transcribing it into the messenger RNA and then the messenger RNA is going to bring the message elsewhere in the cell.

Next comes translation, that messenger RNA is used as a template for synthesizing a new protein. Transfer RNA or TRNA brings the amino acids in anticodon necessary for protein synthesis and something to remember, is that genes are read three nuclei at a time in units called codons. You look at the three nuclei types that are coding for this one protein and they’re going to be transcribed onto messenger RNA, which is going to travel elsewhere in the cell and transfer RNA is going to bring the amino acids and the anticodon that match up with that set of three, with that codon. Let the protein be created.

Let’s look at that over here, let’s pretend this genes sequence came from a strand of DNA and remember your bases are adenine, guanine, cytosine and thymine. We are going to say it’s going to change from DNA to the messenger RNA, so we’re transcribing here and each base must be transcribed. Here we’ve got our transcription, so the guanine is going to transcribe to cytosine, cytosine to guanine, thymine to adenine, cytosine to guanine, thymine to adenine and thymine to adenine. The messenger RNA is going to carry this sequence, so you can see how it isn’t exactly what was on the DNA, it’s what base would have paired with the DNA.

It’s kind of like a code you’ve got to sit here and figure out, you got to decode what the messenger RNA says. The messenger RNA has the pairs that would have gone with the DNA and so in comes your transfer RNA, which is going to have its the amino acids and the anticodon that’s necessary for each of these. Each set of three is a codon and it gets transferred over and so now the transfer RNA is going to come in and it’s going to bring what we need. It’s going to say, okay, we have cytosine, so now we need the guanine and then it’s going to bring cytosine back to pair with the guanine, thymine back to pair with adenine, cytosine back to pair with guanine, thymine to pair with adenine and thymine to pair with adenine.

Now, on a different part of the cell, you’ve got these codons and they’re going to code for a certain protein and this is what happens in the cell, so this part will be your translation. You’ve got strands of DNA, part of the cell says oh, I need a certain protein, well this codon sets codes for one of the proteins you need and this codon codes for one of the other proteins you need. The DNA is going to send it. The messenger RNA is going to hold the transcription which is where it’s changed to what the pairs would be. What pairs with each base is going to be the transcription that goes on the messenger RNA and then the messenger RNA travels off into the cell to where the cell protein is needed.

The transfer RNA is going to bring the bases plus amino acids and then you’re going to get these bases plus the new amino acids are going to give you your proteins that these codons were coding for. You’ve got your transcription, where it’s coded onto the messenger RNA and then you’ve got translation where it’s decoded and the transfer brings in what you need, plus amino acids in your proteins are created. That’s kind of a complicated process, but it’s what genes do. That’s their job, their job is to send messages throughout the cell, so that new proteins can be created and they’re going to carry your hereditary information. They have the basic instructions necessary to tell your body how to carry out the hereditary processes and keep producing the cells and the proteins that you need and maintaining your cells. Just keep in mind, genes are units of hereditary information and they carry messages throughout the cell and instruct the cell on how to create the proteins that your body needs.

The next lesson: Genetic vs. Environmental Traits, both lessons are included in Practice Tests.

genes