[Catalist] Genetics question for Bio/ Human Bio Teachers

[Sarah Kelley]

Hi Greg

The question states “what is the probability that they will produce an affected daughter?”, indicating that there is the possibility of having a boy, the girl is not the guaranteed gender of the unborn child so the probability would be 25%.


Sarah Kelley
Year 7 Learning Coordinator | Science Teacher
Presbyterian Ladies' College | 14 McNeil Street, Peppermint Grove WA 6011
Tel: +61 8 9460 6122 | http://www.plc.wa.edu.au<http://www.plc.wa.edu.au/>




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From: Catalist <catalist-bounces at lists.stawa.net> on behalf of Lauren Clarke <lozzclarke at gmail.com>
Reply-To: "catalist at lists.stawa.net" <catalist at lists.stawa.net>
Date: Thursday, October 26, 2017 at 11:08 AM
To: "catalist at lists.stawa.net" <catalist at lists.stawa.net>
Subject: Re: [Catalist] Genetics question for Bio/ Human Bio Teachers

Hi Greg,

In my experience the question has already specified that it’s asking about a girl, so you remove the chances of boys and then you look at the resulting genotypes of the girls so I agree should be 50%
Lauren Pascoe
Sent from my iPhone

On 26 Oct 2017, at 9:51 am, Greg Munyard <gmunyard at kennedy.wa.edu.au<mailto:gmunyard at kennedy.wa.edu.au>> wrote:
Good morning folks

My colleagues and I are having some discussion around this question and I wondered if there is a consensus in the Bio/ Human Bio community on this:

“If II-8(XnY) and II-9 (XNXn) have more children, what is the probability that they will produce an affected daughter?” (Genotypes not in the original question – had to be ascertained from a pedigree.)

One colleague’s approach is to say that there is a 50% chance for producing a daughter and 50% chance that a daughter will be affected so the combination of these is a probability of 25%.

My approach is to say that there is zero chance for sons to be daughters so that they represent a null sample. Considering only daughters then the chance of an affected daughter is 50%.

Any guidance out there in the ether?

Regards

Greg Munyard
Senior Teacher – Science
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