Exam stats:
- Mean score: 79 (86 in exam 1)
- Standard deviation: 10.9 (8.8 in exam 1)
- Mode: 82 (90 in exam 1)
Scores were down in average and the standard deviation increased compared to exam 1. Most likely because of the material being newer for most students, and a little more complex. Any other hypothesis?
Score frequency distribution
Toughest questions (statistically):
12. Mutation rate can be measured experimentally...
b. comparing the genomes of an ancestor and its descendants
Comment: A bacterial genome can be sequenced, then culturing the strain for a number of generations, and then sequencing the genome of a descendant. By comparing both genome sequences and knowing the number of generations past, the mutation rate can be measured.
13. Mutation rate can be masured by observation...
c. comparing the genomes of multiple species
Comment: When generation times are too long to actually allow many generations to go by (e.g. in mammals) an experimental measurement of mutation rate is not possible. In such cases it can be estimated by comparing the genomes of multiple related species and measuring generic distances.
20. A primer strand...
b. is the strand of DNA being extended
Comment: Primer strand is the technical term for a "daughter" strand, whereas template strand is the name for the "parent" strand. Most people circled the answer for 'what is a primer'. A primer is a strand of oligonucleotides, but it's not called 'primer strand'. Just 'primer'.
25. Single strand DNA-binding proteins...
e. straighten the template strand during relpication
Comment: They prevent the single tremplate strand of forming loops that can interfere with the reading of the DNA plymerase.
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