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GS-3 Section III Question 40

GS-3 Section III Question 40

Postby admin » Wed Aug 11, 2010 3:36 pm

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Re: GS-3 Section III Question 40

Postby Chris777 » Mon Mar 10, 2014 10:40 am

In Q40 of the GS 3 exam the question asks about organism 9 but the answer only refers to organism 6 and does not make any sense of how the answer relates to organism 9. If someone could help it would be appreciated.
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Re: GS-3 Section III Question 40

Postby goldstanda3269 » Thu Mar 13, 2014 11:25 am

The reason is that the clue given regarding organism 9 provides information that requires a reevaluation of the entire flow chart. Since the answer choices involve organisms 1, 2 and 3, those 3 organisms need to be reassessed given the new information. Of course, the 'new' information is that if organism 9 lacked any of the 3 traits then A is recessive. This is the only valuable information regarding organism 9.
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Re: GS-3 Section III Question 40

Postby Chris777 » Thu Mar 13, 2014 4:05 pm

Thank you, for your help.
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Re: GS-3 Section III Question 40

Postby RosieMcFadyen » Fri Sep 02, 2022 11:24 pm

I'm confused with this one, if organism 9 lacks all of the traits, surely it does not mean A has to be recessive, it could just mean that 9 inherited the recessive allele a from both parents and 3 is heterozygous no?
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Re: GS-3 Section III Question 40

Postby goldstanda3269 » Wed Sep 07, 2022 6:28 pm

The only thing similar to your question that we can see is question 22?

"22) If organism 9 were an open, solid-line organism (i.e. if it lacked any of the three traits), which of the following would necessarily be true?"

We will respond based on this assumption...

RosieMcFadyen wrote:I'm confused with this one, if organism 9 lacks all of the traits, surely it does not mean A has to be recessive, it could just mean that 9 inherited the recessive allele a from both parents and 3 is heterozygous no?


Not really. If 9 inherited the recessive allele a from both parents then 9 would express Trait A. However, the question is stating "If organism 9 were an open, solid-line organism (i.e. if it lacked any of the three traits)" which means that in this hypothetical, 9 is NOT expressing Trait A.

Consider this: Organism 3 has Trait A. If it is homozygous dominant then all offspring will express Trait A which is not the case. If it is heterozygous then we expect that, in a large enough pool, 50% of offspring would express Trait A which may have been the original situation suggested by Figure 1.

However, the question stem for 22 changes Organism 9 such that none of the offspring expressed Trait A which suggests that Organism 3 was homozygous recessive for Trait A and produced offspring that are carriers but do not express Trait A.

Going a little further: Notice that Trait A carriers 8 and 9 can therefore produce offspring that are homozygous recessive (14 and 15).
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