William Cope
Yerko Berrocal
Richard Tapping
Anthony Dwyer
Alisha Punjwani
Dean WatkinsTBL Group 10 - E-Team Based Learning’s Updates
Application Problem 2
A woman is a balanced carrier of a Robertsonian translocation involving chromosomes 14 and 21. Her husband is chromosomally normal. They have two children: a daughter who is a balanced translocation carrier and a son with translocation Down syndrome. Given below are genotypes for a polymorphic marker on the long arm of chromosome 21.
Mother: [1,2]
Father: [2,2]
Balanced carrier daughter: [1,2]
Translocation Down syndrome son: ?
Based on the genotypes given for three family members, which of the following predicts the genotype of the translocation Down syndrome son?
A. 1,1
B. 1,2
C. 2,2
D. 1,1,2
E. 1,2,2
INSTRUCTIONS:
- Draft your response in the comment area below. Your answer explanation should illustrate your thought process in as much detail as possible. Post your response once you have a complete explanation of your reasoning. Do not refresh your browser until you have posted your comment.
- Now refresh your browser. Read and comment on the responses of others from your team. Suggest extensions or modifications to their ideas. Refresh your browser regularly to view and respond to new comments from your team. The product of your team discussion should be an answer choice (to enter in Benware) and a well-reasoned justification for the answer your team chooses.
- Your team reporter should now enter your answer in Benware and the whole-class discussion of this application exercise will take place verbally as usual.
I love all the comments, but this constant refreshing is tough
yeah it feels quite inefficient
It is definitely easier to talk it out face to face via zoom
Agreed
E. Since the son has the translocated gene, he had to have gotten 1 from mom. Only possible gene from dad is 2. And a third gene would be needed to result in Down syndrome, so only gene left is 2, either from mom or dad.
That was more or less my reasoning as well
Yeah I'm thinking E as well
I was able to remove C because chromosome 1 is the translocated chromosome from the mother that is since her daughter who is a carrier.
I then removed options A and B because if her daughter is phenotypically normal, her affected son should not have the same genotype as the daughter and because its a trisomy that leaves me with D and E.
My final answer is D, because the affected chromosome in question is 1, therefore answer D. 1, 1, 2 makes most sense to me.
E seems to be the most likely answer to me, but I'm not entirely sure on the reasoning. I was thinking that the son with Down Syndrome inherited the translocated 14/21 chromosome as well as a normal 21 chromosome from the mother (1,2) and then just one normal chromosome 21 (2) from the father to give trisomy 21.
This reasoning makes more sense to me now than mine, D.
So you're saying think of 1 as chromosome 14 and 2 as chromosome 21? If so, then yes, 1,2,2 makes sense.
E.
It definitely would not be C. B results in a carrier. I guess not A or D because there is only one 1 present in the parents?
but maybe it is D because 1 is the problem gene.
Yeah Morgan, I agree with ruling out A and D