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 Lecture on Random Mating

January 9, 2019
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0:00 let's talk a little bit alright I talked

0:02 a little bit earlier about random mating

0:04 but it's a key assumption under which

0:06 you guys are operating when you

0:08 calculate with a product rule

0:10 calculation in pop stats by saying P

0:14 squared + 2 PQ you were assuming

0:16 hardy-weinberg equilibrium okay one of

0:19 the key components of that isn't random

0:21 mating so random what is random first

0:26 when someone says I chose these people

0:30 from my clinical study at random okay

0:35 I've been in a medical school for a long

0:37 time we've done a lot of medical studies

0:39 I put things up in the elevator

0:41 sometimes we want people to come in and

0:43 give us their blood okay and in a

0:48 medical school who do you think's in a

0:49 medical school medical students graduate

0:52 students anytime you go to select

0:55 anybody there's maybe some level of

0:57 criteria right like so if I was doing a

1:00 population study in diabetics you know

1:03 there's a big difference in diabetes

1:05 between African-Americans and Caucasians

1:06 right I was doing a study in diabetics

1:09 wouldn't I want the control group to be

1:12 of the same racial classification as the

1:14 test group were the question group yeah

1:17 so I'd have to impose a selection so

1:20 it's not random right it's just such a

1:22 thing as random no there isn't but the

1:30 caveat tall this is random is only with

1:33 respect to the parameter being studied

1:36 remember that because if I'm studying

1:41 certain receptor levels on the islet

1:45 cells for diabetics certain levels of

1:49 the presence of a receptor well I don't

1:52 have any preconceived knowledge of how

1:55 many receptors our cameraman is gonna

1:57 have on his eyelid cells if I select him

2:02 as a control for a study the ish the

2:07 thing I'm studying is random with

2:09 respect to that so in these genetic

2:12 studies

2:13 when you go out and you select a group

2:15 to genotype to count their alleles you

2:18 don't know their genotypes a priori you

2:22 know that they belong to some kind of a

2:23 group in the clinical study I wouldn't

2:26 know how many receptors they had on

2:27 their islet cells unless they had

2:31 diabetes so we'd have the diabetes group

2:33 and then the control group was the only

2:35 way it's random is you don't have

2:36 diabetes right and you're of a certain

2:38 racial category because we know there

2:40 are differences in the prevalence of

2:43 diabetes between the major racial

2:44 categories so remember that when the

2:47 defense attorney says to you we're these

2:50 people really selected randomly they got

2:54 them from blood banks well that's random

2:58 with respect to the STR you can pick

3:00 them that okay the other thing that

3:02 comes into random is the mating part and

3:06 I talked to you a little bit in the very

3:08 beginning of the course and this morning

3:10 about mating it's based on continental

3:13 proximity the point being is that you

3:16 don't choose your mate based on your

3:17 genotypes and it came up in our court

3:19 case and the curl and the DES redirect

3:21 by the DA was so when you chose your

3:24 wife did you know her V W a type and her

3:28 fg8 I said no I didn't and he says and

3:31 you're the one person that could have

3:33 right I said yeah I probably could have

3:35 but she wouldn't let me I said we got a

3:37 big laugh and the jury laughs and

3:39 everybody laughed well all the defense

3:42 attorney knew was the random mating he

3:45 just wanted to play around with the word

3:46 random mating that's why I'm trying to

3:49 really nail it down for you it's random

3:51 with respect to the parameter being

3:53 studied and the mating may not be random

3:56 with respect to race and geographical

3:59 proximity but it sure is with respect to

4:02 the STR genotypes right okay
    
  
Disclaimer:
              Opinions or points of view expressed in these recordings represent those of the speakers and do not necessarily represent the official position or policies of the U.S. Department of Justice. Any commercial products and manufacturers discussed in these recordings are presented for informational purposes only and do not constitute product approval or endorsement by the U.S. Department of Justice.
  
Date Published: January 9, 2019
    
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