What Are The Basic Genetic Terms? Video

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This is so good, I was so confused about all of the genetic tests.

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What Are The Basic Genetic Terms?

Host: Genetic counselors and genetic experts use a lot of terms, we never were able to find it correctly. First of all, what is a chromosome? Lakshmi Mehta: That's a good question and it's a very common problem we face. Residents are always ordering the wrong test. They order the chromosome test versus the gene test, so I am glad you asked that question. Host: So what is a chromosome? Lakshmi Mehta: So the chromosome is basically a physically visible structure that you can see under the microscope, and it's a very very long strand of complex genes. Host: How many do we have as a human being? Lakshmi Mehta: We have 46 chromosomes, they are in pairs. We have 22 pairs of autosomes and one pair of sex chromosome, the X and Y. Host: What makes a boy and girl different? Lakshmi Mehta: It's the Y chromosome that determines sex, so in the absence of the Y chromosome, by default you develop this female. Host: So girl is a what? Lakshmi Mehta: A girl is XX, the 46 chromosome. Host: And a boy is of what? Lakshmi Mehta: XY. Host: So there is all kinds of variations in this, okay. Then you mentioned gene? What's a gene, if this is what we say chromosome, what's a gene. Lakshmi Mehta: So chromosomes are complexed genes. So if you open a chromosome up, it's going to be a very long strand of genes, almost like beads on a chain, so each bead is the gene, and interspersed between the genes, is DNA, but the DNA in between the genes, we still don't know the function of. So they have the tendency to calling like -- Host: You mean we don't know the whole story?. Lakshmi Mehta: No. Host: Oh we'll learn it. Lakshmi Mehta: No, we don't, that story at all. Host: We use letters like P and Q, what does that mean?. Lakshmi Mehta: Alright, the structure of the chromosome in the nomenclature, the way you describe a chromosome. Every chromosome has a little constriction, and that constriction can be towards the top of the chromosome, it can be in the middle, it's called the Centromeres. It sort of holds the chromosome together. Above the chromosome is what we call the P arm of the chromosome, the petit arm, the French, "petit" meaning small. Host: Petit, petit. Lakshmi Mehta: And the Q just came because it followed P. So Q is the long arm, the arm below the centromere, and it's not always longer, and the P arm is the arm above the chromosome. The portion of the chromosome above the centromere. Host: So sometimes you are missing P or missing Q. Lakshmi Mehta: Exactly. Host: Or a little bit too much of this, and too much of that, and it forms all these disease, is that correct? Lakshmi Mehta: Actually even there are chromosomes that even normally don't have any P arm. So we call them acrocentric chromosomes, like the common chromosome that we've all heard about, chromosome 21, that causes down syndrome, really doesn't have too much above the centromere, all the important material is below the centeromere, so it has very little P arm and a lot of Q arm. Host: And trisomy means what? Lakshmi Mehta: Trisomy means three copies of a chromosome. Host: That's all it means? Lakshmi Mehta: That's all it means, three copies of a chromosome. The normal chromosomes are disomic. We have two copies of a chromosome. If you have an additional copy, it becomes trisomy. Host: So the map of these things indicates different diseases or potential diseases sometimes. Lakshmi Mehta: That's a bit more complicated. The chromosome. Host: Wait, wait, wait, make it simple. I don't want to walk out today, without knowing what I am talking about. Lakshmi Mehta: This is a little guide to genetics. Host: That's right. Lakshmi Mehta: Overall if you have an abnormality in the chromosomes, visible abnormality in the chromosome, meaning that there is an extra chromosome or a missing chromosome or a piece of a chromosome, extra missing. That's going to cause a certain expectation. You'll have an expectation of birth defects, unusual appearance, growth problems and developmental delay. Sometimes mental retardation, not always, and that's because when you visibly can see chromosome abnormalities, that means there is a whole set of genes extra missing. That's at one level. Host: I think it is acting like a fragile -- [Note: This audio ends abruptly]

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Host: Genetic counselors and genetic experts use a lot of terms, we never were able to find it correctly. First of all, what is a chromosome?

Lakshmi Mehta: That's a good question and it's a very common problem we face. Residents are always ordering the wrong test. They order the chromosome test versus the gene test, so I am glad you asked that question.

Host: So what is a chromosome?

Lakshmi Mehta: So the chromosome is basically a physically visible structure that you can see under the microscope, and it's a very very long strand of complex genes.

Host: How many do we have as a human being?

Lakshmi Mehta: We have 46 chromosomes, they are in pairs. We have 22 pairs of autosomes and one pair of sex chromosome, the X and Y.

Host: What makes a boy and girl different?

Lakshmi Mehta: It's the Y chromosome that determines sex, so in the absence of the Y chromosome, by default you develop this female.

Host: So girl is a what?

Lakshmi Mehta: A girl is XX, the 46 chromosome.

Host: And a boy is of what?

Lakshmi Mehta: XY.

Host: So there is all kinds of variations in this, okay. Then you mentioned gene? What's a gene, if this is what we say chromosome, what's a gene.

Lakshmi Mehta: So chromosomes are complexed genes. So if you open a chromosome up, it's going to be a very long strand of genes, almost like beads on a chain, so each bead is the gene, and interspersed between the genes, is DNA, but the DNA in between the genes, we still don't know the function of. So they have the tendency to calling like --

Host: You mean we don't know the whole story?.

Lakshmi Mehta: No.

Host: Oh we'll learn it.

Lakshmi Mehta: No, we don't, that story at all.

Host: We use letters like P and Q, what does that mean?.

Lakshmi Mehta: Alright, the structure of the chromosome in the nomenclature, the way you describe a chromosome. Every chromosome has a little constriction, and that constriction can be towards the top of the chromosome, it can be in the middle, it's called the Centromeres. It sort of holds the chromosome together. Above the chromosome is what we call the P arm of the chromosome, the petit arm, the French, "petit" meaning small.

Host: Petit, petit.

Lakshmi Mehta: And the Q just came because it followed P. So Q is the long arm, the arm below the centromere, and it's not always longer, and the P arm is the arm above the chromosome. The portion of the chromosome above the centromere.

Host: So sometimes you are missing P or missing Q.

Lakshmi Mehta: Exactly.

Host: Or a little bit too much of this, and too much of that, and it forms all these disease, is that correct?

Lakshmi Mehta: Actually even there are chromosomes that even normally don't have any P arm. So we call them acrocentric chromosomes, like the common chromosome that we've all heard about, chromosome 21, that causes down syndrome, really doesn't have too much above the centromere, all the important material is below the centeromere, so it has very little P arm and a lot of Q arm.

Host: And trisomy means what?

Lakshmi Mehta: Trisomy means three copies of a chromosome.

Host: That's all it means?

Lakshmi Mehta: That's all it means, three copies of a chromosome. The normal chromosomes are disomic. We have two copies of a chromosome. If you have an additional copy, it becomes trisomy.

Host: So the map of these things indicates different diseases or potential diseases sometimes.

Lakshmi Mehta: That's a bit more complicated. The chromosome.

Host: Wait, wait, wait, make it simple. I don't want to walk out today, without knowing what I am talking about.

Lakshmi Mehta: This is a little guide to genetics.

Host: That's right.

Lakshmi Mehta: Overall if you have an abnormality in the chromosomes, visible abnormality in the chromosome, meaning that there is an extra chromosome or a missing chromosome or a piece of a chromosome, extra missing. That's going to cause a certain expectation. You'll have an expectation of birth defects, unusual appearance, growth problems and developmental delay. Sometimes mental retardation, not always, and that's because when you visibly can see chromosome abnormalities, that means there is a whole set of genes extra missing. That's at one level.

Host: I think it is acting like a fragile --

[Note: This audio ends abruptly]

Transcription by: Scribe4you Transcription Services