Dr. Cotton.
Robin Cotton, called as a witness by the People, was sworn and testified as follows:
Please raise your right hand. You do solemnly swear that the testimony you may give in the cause now pending before this Court, shall be the truth, the whole truth and nothing but the truth, so help you God?
Please have a seat on the witness stand and state and spell your first and last names for the record.
All right. Dr. Cotton, why don't you just lean back and pull the microphone towards you, please.
All right. Thank you. Ladies and gentlemen, my name is George Clarke. Actually has an "e" on the end. So I'm no relation to Miss Clark. Thank you, your Honor, and good morning, ladies and gentlemen.
I think you need that disclaimer, your Honor. My brother.
DIRECT EXAMINATION BY MR. CLARKE
KEY QUOTEWe are a private company and we do DNA testing for paternity and for criminal cases.
As far as your formal education, do you have any higher level or upper level degrees?
I have a masters degree with a major in biology and I have a Ph.D. with a major in biochemistry and molecular biology.
It's just the methods and information that's gathered by those methods in an attempt to understand basically all cellular processes.
Well, except for viruses, all organisms are made up of cells. Bacteria is a cell, a yeast is a cell, and we are made up of many, many cells, and biochemistry and molecular biology are the tools that a biologist uses to try to understand how cells function and how they are able to do the things that they do.
That's fine. Thanks. You also described that your higher level of degree was also in molecular biology; is that right?
Molecular biology is sort of a generic term and really refers to a set of tools that biologists may use to help them understand any number of things. Maybe a biologist would use the tools of molecular biology to find out where a particular gene or genetic characteristic was or they might use the tools to understand how a particular gene or genetic characteristic causes a cell to do a particular thing. And that can be applied to research in animals and research in humans, research in bacteria. It's really the set of tools that is used in understanding cellular processes.
Most of my graduate--well, actually the work that I did for my masters degree didn't have anything to do with DNA. The work that I did for my Ph.D. and research that I've done since then has all had something to do with understanding DNA.
All right. I would like to return to your qualifications later. But first, what is DNA, Dr. Cotton?
DNA is that part of the chromosomes that carries the information that programs an organism from the point of conception; that is from the point when an egg and a sperm come together. The DNA in the egg and the DNA in the sperm now makes up the total DNA for that organism, and the information in that DNA programs the development of that organism all the way through childhood, if it was a human, adulthood and on through aging until that human being isn't alive anymore.
KEY QUOTEDNA is a--is correctly described as a polymer. That is, it's a long series of components that are all attached together and it's basically our cellular alphabet.
When the egg and the sperm come together to start a new animal or a new human being, the egg contains half of the DNA from that human being--for that new--we'll talk about people so I don't have to keep referring back and forth, people, animals. It's generic. But anyway, the egg contains half of that DNA for that new person, the sperm contains the other half. So we inherit one half of our DNA from our mother and we inherit the other half of our DNA from our father.
As far as DNA's role in the body--and you've described the fact that it provides for the structure, for instance, of human beings; is that right?
And when you say "structure" or I've used the word "structure," what role does DNA have in creating our bodies?
You could take an entire series of college courses that would answer that question. So let me see if I can make a simple answer for you. All of the information that predicts our structure, our height, our build, our skin color, our organs, you have a liver, that information on how that liver is going to be formed as the organism developed is contained in the DNA; and the DNA does that by containing the information that's eventually translated into proteins, and those proteins do the major part of the work in the cell. And so basically the DNA contains all information to make a specific organism.
Well, if you think of a blueprint as all--I don't know much about how you build a building, but if I--if we make the assumption that a blueprint contains all the information for how to build your house, the DNA--the analogy is, the DNA contains all the information on how to build you.
Okay. Do we have and in fact have you and I discussed the fact that we will be drawing some charts for this jury?
And will we in fact be talking to your knowledge about some of these very same items that you've just described?
The chromosomes are really the DNA molecules packaged up in what's a more manageable form for the cell. There are 46 chromosomes and you get 23 of those from your mother, you get the other 23 from your father, and the chromosome is literally the DNA molecule packaged up by some proteins. So we'll sort of disregard those proteins. We don't really care about those for purposes of this discussion. But there would be if there--since there are 46 chromosomes, there are really 46 molecules of DNA in each nucleus of each cell of a human being.
Would it help to illustrate that point about chromosomes and DNA for you to draw a chart for the jury?
All right. Your Honor, then with the Court's permission, may the witness utilize the tripod that Mr. Fairtlough has--
Well, the problem is, I need--Defense counsel needs to be able to see it as well. So what we'll do is, after we complete the drawing, we'll exhibit it to the full jury panel.
All right. Very well. Your Honor, perhaps this--what will be I believe a drawing by the witness be marked as People's next in order.
All right. And let's see if we can move that back so we're not cutting off juror no. 1.
I'll just ask Mr. Fairtlough to move that back so we're not cutting off juror no. 1 here.
I was going to suggest if we could use the other tripod for the drawings, that will get it higher I think.
Well, let's make due with what we have here and then we'll exhibit it to the jurors.
All right. Dr. Cotton, then with the Court's permission, could you use this chart that's now been marked or will be shortly marked People's exhibit 235 to describe for the jury this concept of DNA and chromosomes?
I'm sorry, your Honor. Perhaps it could be turned a little bit so the Defense can see it.
I understand that, counsel, but it's going to be exhibited for everybody. We have to make do with the angles we have.
And is there a color, Dr. Cotton--do you have a pen in your hand? All right. Very good. Then if you could, please, for the jury describe again DNA and this concept of chromosomes and its packaging.
Let's go back just briefly to the fact that we have each in each cell 46 chromosomes. These come 23 from mother and 23 from father.
Mr. Goldberg, Mr.--I'm sorry. Can we just have you--Mr. Goldberg, could you give Mr. Neufeld that seat, please, and slide over a little? All right. Proceed.
To make a very simplistic drawing of a cell, you have the nucleus somewhere in the middle which contains the 46 chromosomes. The rest of the cell on the outside is referred to as cytoplasm. And just as fast as I write this down, you don't really need to know or remember this. We're just going to focus on the DNA that's in the nucleus. People who are expert at looking at chromosomes under a microscope can distinguish the 46 chromosomes as pairs because they stain slightly differently if you put a dye on them and they have somewhat different shapes. So we'll just make a crude drawing here of a chromosome pair. And someone who is expert at this could actually say, well, this is chromosome pair no. 1, and the pairs are numbered 1 through 23 and very well characterized. So to look at it under a microscope, if I could find each of the two chromosome no. 1, I couldn't tell which came from mother and which came from father by looking at them, but will just in my example here say that this first one came from the father and the second one came from the mother. Now, if you think of the chromosome as the packaging of the DNA, if you unwind the DNA from the chromosome for each one, you would have a very long thread. And the best analogy that I can give to you is that it's not very different from going and having a spool of thread, and the spool of thread has dimensions that are maybe an inch high and an inch in diameter or something. But if you unwind that thread, it's many yards long. And in the same way, if you unpackage the DNA from each individual chromosome, it would be very, very long. And my drawing isn't at all in proportion if I unpackaged--if I had chromosomes that were this size and I unpackaged the DNA, it might be several stories worth of length. So it's a very long thread. If we then look closer at the DNA, we see that each strand is actually what's referred to as being double stranded. And if we did this for an entire cell rather than having just two chromosomes as I've shown here, you would have 46. So you would have 46 long strands of DNA if you were able to unravel each chromosome and lay out each piece of DNA.
In terms of this concept of chromosomes, if DNA were a book, would a chromosome be something like a chapter to a book?
Okay. Now, you've introduced this idea of two strands. What do you mean by two strands to DNA?
Umm, you might want to go to an additional diagram to try to illustrate that better than I could draw here.
Your Honor, this second chart, would the Court prefer to have it marked People's exhibit 236 since the witness went to a second page?
All right. All right. I think we have a prepared diagram, your Honor, that I would ask be marked People's exhibit 237.
Your Honor, while they're displaying the next one, can we show the ones that are already done to counsel or would you rather we wait?
Hold on. We have a break coming up in 10 minutes. So we'll do the other expedition at the break.
Your Honor, for the record, this chart could be identified as labeled at the top with DNA and depicting what appears to be a ladder with various notations.
By Mr. Cotton: Dr. Cotton, with respect to this diagram that's been marked People's exhibit 237, can you describe for the jury, please, what it shows? And we have pointers right at your left hand there, if that would help.
Okay. DNA is two strands wound together to--in a helical formation. And the reason I didn't try and draw it on my drawing here, I just drew two stands side by side is because I can't draw this shape very well. But the two strands are wrapped around as if you took two ribbons and twisted them one around the other. DNA has four basic component--components. They are referred to as bases spelled b-a-s-e-s. So there are four bases that make up all the DNA, and they have the names adenine, guanine, thymine and cytosine. And they are abbreviated--just by their first letter, A, T, G and C. These form bases are the DNA alphabet. They exist along the length of the DNA molecule in a specific order, and that order has meaning to the cell. And it's just like if you look at the English alphabet, it has 26 letters, and you can put those letters together in--to make words, which in turn make sentence which in turn make paragraphs. The order of these four bases or four components on the DNA has meaning to the cell and that order is translated into information that the cell can use.
The other important or another important feature is that these four components or bases come in pairs. Along one strand, you'll have some particular order. So this order is first a G, then an A, then another G, a T, a C and a T. Always across from a G, there is a C. So people talk about a base GC being one kind of base pair. Always across from a t is an A. So in the DNA, there are two kinds of base pairs, an at pair or a GC pair. They are paired together like that and the pairing is very specific because in the structure of the molecule, this distance from one strand to the other strand is constant, and if you add up the distance that a C takes or the space that a C takes up and you add up the space that a G takes up, it's always the same and it is the same as the space that an at pair takes up. So if you can think of it as if you had a zipper, but you had four different shaped teeth and the zipper would only come together when every a was paired with a t and very G was paired with a--every G was paired with a C.
Would it then be correct that if a G was paired with an A, that it simply wouldn't match or stick together?
Well, if--if there was a single mismatch like that, then it would be very loose there. But you can't have a lot of mismatches or the two strands won't stay together.
Incidentally, this structure of DNA as you've described it, when was it discovered?
Dr. Watson and Dr. Quik--Cripp--Crick and I believe that the article was published in 1953.
As far as this diagram--and it shows these A's and T's that match at least in three instances and then it looks like three more instances where the g's and the C's match, is this simply a small portion of an entire segment or an entire molecule of DNA?
A very small portion. There are altogether six billion base pairs. And this is of course an approximate. But in human beings, you would have six billion base pairs of information. One of the important things to note from this diagram is that when people talk about DNA, you talk about DNA as being a particular length. It is possible to get a physical measurement of the length, but that's not the common way that it's discussed. People talk about--scientists talk about DNA in terms of how many base pairs long a particular piece of DNA is. So the particular piece of DNA that's on this diagram is one, two, three, four, five, six base pairs in length. And you can discuss DNA and it is discussed in terms of how many base pairs long is a particular piece.
When you described the entire molecule being roughly six billion bases, is that in each cell of our bodies that has a nucleus?
No. That is almost all cells. And the major exception or the only exception that I commonly would refer to--in fact, I'm not sure if there are others or not--is red blood cells. And red blood cells in the development and the formation of a red blood cell, the nucleus is lost and there is no nucleus in a red blood cell. So if one were to get DNA from blood, the DNA is not coming from the red blood cells. It's coming from the white blood cells.
While we're on that topic, can you describe, please, what are the various sources of DNA; in other words, various parts of the body that DNA can be taken from?
Well, DNA can being taken from almost any source. You can get DNA from bone, from any tissue, liver spleen, pancreas, kidney, brain, skin if you have enough blood, semen, hair roots. Not the part of the hair that you're washing and combing. It's just protein. If you pull out a hair and you get the hair follicle with it, there are cells around that that are part of that hair follicle, and they contain DNA.
All right. As far as this structure--and you've described on this chart the fact that DNA is shown here in a double stranded form?
It can be made to be single stranded. It occasionally in the process of making two cells out of a single cell will exist for short stretches in single-stranded form, but that's again something we really don't need to be worried about. But experimentally, you can take a piece of DNA and either treat it with heat, which would be the common method--and if you think of this as a zipper, the two strands will simply come apart, so that you would have one strand that had a G, A, G, T, C, then the other strand would have a C, T, C, A, G. So it's like unzipping the zipper. You can do that chemically. You can do it with heat and you--and because of the specific nature of the base pairing, you can also bring it back together. The two--two single strands will come back together as long as each G is paired with a C and each a is paired with a T. So, again, it's like having that zipper have four different shaped teeth and the only way you can zip it up is if all the teeth mesh together properly and a with a t and a G with a C.
All right. Your Honor, I was going to have the witness start with a new drawing. Would the Court prefer that now or--
No. We need to take a break for a juror issue. All right. Ladies and gentlemen, please remember all of my admonitions to you; do not discuss the case amongst yourselves, don't form any opinions about the case, do not conduct any deliberations until the matter has been submitted to you, do not allow anybody to communicate with you. We'll stand in recess for 15 minutes. All right. Mr. Clarke, in the interim, would you show the exhibits, please. Mr. Clarke.
DNA is that part of the chromosomes that carries the information that programs an organism from the point of conception...the DNA contains all the information to make a specific organism.
There are altogether six billion base pairs...in human beings, you would have six billion base pairs of information.
If one were to get DNA from blood, the DNA is not coming from the red blood cells. It's coming from the white blood cells.
I think you need that disclaimer, your Honor. My brother.