4. The plot below shows %GC content (Y axis) vs DNA melting temperature in Cells

Question

4. The plot below shows %GC content (Y axis) vs DNA melting temperature in Cells(X axis) for various organisms. Refer to the plot to answer questions 4a through 4c below. 100F 80 Mycobacterium phle 60- Serratia Salmon sperm 40 Yeast T4 20F AT-DNA 60 80 90 100 110 T(C) a. From this plot, what is the relationship between %GC content and melting temperature? Explain this relationship in the basis of chemical bonding within a double stranded DNA molecule. b. What is the organism with the highest %AT content? C. Based on the plot, what is the %GC content ofSerrata? Determine the %AT content from this information.

Explanation / Answer

A) As the GC content increases, Tm increases with it. Meaning they are directly proportional to each other.
Double stranded DNA molecule containes either A-T bonding ( 2 hydrogen bonds) or G-C bonding ( 3 Hydrogen bonds) and since increasing the number of Hydrogen bonds makes the bond harder to break, more energy is needed to break G-C bond than A-T bond and hence increasing the GC content also increases the temperature required to melt the DNA molecule.

B) Highest AT content is in Bacteriophage T4 as it has the lowest GC content so rest should be AT content.

C) GC% of serratia is 60% which means the AT content should be 40%.

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