| Q: | A strand-break temperature for a particular DNA molecule is defined as a temperature at which exactly 50% of the A-T bonds in a strand of DNA are split. If this temperature is 120 degrees celcius for a particular DNA strand, which of the following is true?
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| A | | greater than 50% of the C-G strands will be broken at the strand break temperature |
| B | | less than 50% of the C-G strands will be broken at the strand break temperature |
| C | | exactly 50% of the C-G strands will be broken at the strand break temperature |
| D | | we cannot know the status of the C-G strands from the information provided |
The correct answer here is B. We need to remember that bonds between A and T consist of two Hydrogen bonds, whereas bonds between C and G consist of three Hydrogen bonds. Thus, the temperature at which half of the weaker A and T bonds are split isn’t necessarily a high enough temperature to split half of the stronger C-G bonds.