It is worth 100 points. There were 80 multiple-choice questions, worth 1 point each, and 6 short essay questions. 4 questions were worth 4 points, and 2 of them were worth 2 points.
Exam stats
- Mean score: 79 (exam 1: 86; exam 2: 79)
- Standard deviation: 15.3 (exam 1: 8.8; exam 2: 10.9)
- Mode: 77 (exam 1: 90; exam 2: 82)
Although the average was steady compared to exam 2, the mode decreased and the standard deviation increased. The likely reason is that the new material that was heavily weighted compared with exam 1 was difficult for some people. But some people had very high scores. Maybe studying more at the beginning of the semester crated a solid base to build upon?
Score frequency distribution
Toughest questions (statistically):
13 & 20. If two genes in an individual are derived from a single ancestral gene, they are called
c & d. Paralogs
Comment: The questions were phrased slightly differently, but the essence of the question and the answer were the same. If an indidual has two (or more) genes in its genome, originated from gene duplications, the are called paralogs or paralogous genes. Orthologs or orthologous genes, the alternative, are genes, in genomes of different species, that have evolved from the same gene in an ancestor. They are the same gene, in different species, not a product of a gene duplication.
43. What is an operon?
a. a series of genes transcribed into a single mRNA in prokaryotes
Comment: Not just they are transcribed into a single mRNA, but are controlled by a single promoter. They are not found in eukaryotes, where each individual gene has its own promoter, and it's transcribed into a separate mRNA.
49. What is an mediator?
d. a complex of proteins that function as an intermediary between transcription factors and RNA polymerase
Comment: There are cases, in complex genetic switches, when having the right transcription factors in place is not enough to start trasncription. The mediator (a complex of 24 subunits), acts as an intermediary (or a coordinator, if you will) between them and the polymerase. It's not a transcription factor per se, but just as important.
57. What is an gene control region?
b. a region of DNA containing elements that control and initiate gene transcription
Comment: The DNA control region can be even longer than the actal gene (introns included). It has several elements that will have to act in coordination to start gene transcription. The gene control region is what makes complex genetic switches complex.
72. If mutation rate cannot be masured experimentally it can be estimated by...
c. comparing the genomes of multiple species
Comment: When generation times are too long to wait around and see how high mutation rate is, the only option is estimating it from the differences found in sequence alignments. There are algorithms that allow the use of nucleotide or amino acid sequence differences as the basis dor such calculation.
84. Describe RNAi. Include the steps in the process and explain its goal
Read pages 493-496 in the text book
Comment: Even though we didn't cover it in class, we did talk about the importance of such process for the cell and in terms of a research tool. I did tell you to read about it and it was specifically mentioned in the study guide as one of the potential topics for open questions.
RNA interference (RNAi) has become an imnportant molecular technique to study patterns of gene expression.
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