Premed students are often traumatized by studying for their MCAT exam, which historically was always taken at the end of their Junior year in college. Now, many medical schools desire a meaningful gap year between completion of an undergrad degree and entrance to medical school so that incoming students have some sort of life-time experience either working, doing research, charity outreach, or traveling during that time. As a result, modern pre-med students often wait to study for their MCAT until after they graduate without realizing that it means they will end up taking two gap years, not one. Students who complete a basics genetic course should be confident with their knowledge about DNA, RNA, and proteins, along with how to solve basic inheritance problems, which will help them on their MCAT exams. Introductory Genetics helps to reinforce concepts taught fleetingly in Introductory Biology.
1. Jiro is told that a bacterium contains a single DNA chromosome containing 15% guanine and then is asked to decide if the organism is âGCâ rich or not (>50% G-C content = 'rich')). With full confidence, Jiro responds:
A.Heck no! The strand has a GC content of 30%.
B.Heck yeah! The strand has a GC content of 70%.
C.Heck no! The strand has a GC content of 15%.
D.It contains exactly 50% GC content.
2. If Marisol isolates 15% guanine from a strand of DNA, she can say with full confidence that:
A.the strand is made up of 70% pyrimidines.
B.the strand is made up of 30% pyrimidines.
C. the strand is made up of 50% pyrimidines and 50% purines.
D.the strand is made up of 70% purines.
3. Jayson is asked if a strand of DNA that is GC-rich will be harder to separate than one that is GC-poor. He responds with full confidence:
A. No!
B.Yes!
C. This question is irrelevant since double-stranded DNA is always easy to separate due to the hydrogen bonds that hold them together.
D.After 150 years of research into DNA, no one knows the true answer to this question.

Respuesta :

Answer:

1. A

2. C

3. B

Explanation:

1. The DNA here has a Guanine(G) content of 15% and as G is equal to C,

[tex]$GC=G+C$[/tex]

     = 15% + 15%

     = 30%

As the GC content is less than 50 % , so the DNA is not a GC rich DNA. Therefore, for a DNA to be GC rich in content, G+C should be more than 50%.

Therefore the correct option is (A), The strand has a GC content of 30%.

2. With a content of 15% Guanine, we calculate the proportions of the four bases. They are :

[tex]$A+T=G+C$[/tex] and [tex]$A=T, G=C$[/tex]

∴ [tex]$A+T=15\% +15\%$[/tex]

              [tex]$=30\%$[/tex]

So when we substract 30% from 100% , we get 70%. Now this 70% is then distributed in the equal proportions for [tex]$A$[/tex] and [tex]$T$[/tex].

Therefore, we have:

[tex]$A=30\%, T=35\%, G=15\%$[/tex] and [tex]$C=15\%$[/tex]

Therefore we calculate the content of purines [tex]$(A,G)$[/tex] and pyrimidines [tex]$(C,T)$[/tex].

Purine content : [tex]$A+G = 35\% + 15\%$[/tex]

                                     [tex]$=50\%$[/tex]

Pyrimidine content : [tex]$C+T=15\%+35\%$[/tex]

                                            [tex]$=50\%$[/tex]

Therefore, the correct option is (C).

3. Yes, the GC rich strand of the DNA is more stable the a GC low content DNA. But this stability is not due to the hydrogen bonds, it is mainly due to the stacking interaction known as base stacking.  

So the correct option is (B).

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