[Catalist] Genetics question for Bio/ Human Bio Teachers

Thu Oct 26 15:56:50 AEDT 2017

Hi,

I am always very careful how I word these types of questions.

What is the chance of an ‘affected daughter’ has two probabilities 1. The chance the child is female (50%) and 2. affected (50%) therefore the combined probability is 25%.

What is thet chance a daughter is affected.  You are now only dealing with the probablility the daughter is affected therefore 50%.

regards

Paul Jefferies
Esperance Senior High School
W: 90719555
M:0400350079

From: Catalist [mailto:catalist-bounces at lists.stawa.net] On Behalf Of Glenda Leslie
Sent: Thursday, 26 October 2017 12:30 PM
To: catalist at lists.stawa.net
Subject: Re: [Catalist] Genetics question for Bio/ Human Bio Teachers

Hi Greg,
I think Ray is on the right track as the question asks about producing the next child. Therefore, have to take into account producing a daughter, then if the daughter will be affected.

Cheers,
Glenda

From: Catalist [mailto:catalist-bounces at lists.stawa.net] On Behalf Of Lauren Clarke
Sent: Thursday, 26 October 2017 11:03 AM
To: catalist at lists.stawa.net<mailto: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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Glenda Leslie
Curriculum Consultant | Science
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