Questions for Biol4241 Midterm Exam, Tues, March 4th, 2026 [Draft of 23 February]


I will choose approximately Six of the questions above. I will require an answer to one of these from everybody. Student may then answer any four of the remaining questions.

[I will improve the phrasing of these questions for clarity over the next two days, and may change the question set slightly.]

1. The discovery of DNA structure continue to be controversy. From the evidence and statements of participants, critique the following statements:

    1) Watson & Crick ripped off Franklin's work, who was badly treated because she was a woman.
    2) Watson & Crick recognized base pairing, which is the key to DNA structure.
    4) Who 'owned' Photo 51? Who was entitled to see it?
    6) Many Grad students: "Two strands or three, bases inside or outside, and you have Chargaff's rules. How long can it take?" Is this realistic?
    8) Chargaff: "I showed them that bases were paired, I wasn't properly acknowledged."

2. "What is a Gene?" Write a one-paragraph essay that that distinguishes Gene, Allele, and Locus
    
3.  Critique the following statements:
        "PAH is the gene for Phenylketonuria (PKU)"
        "PKU" is a genetic disease caused by the absence of the PAH gene."

4. The amino acid replacement Glu Val  in beta-globin  produces Sickle-cell hemoglobin: What is the DNA mutation involved? Explain

5  Symptoms of Huntington Syndrome typically appear post-reproductively:  How does this involve Tiresias' Dilemma: 'It is but sorrow to be wise when wisdom profits not.'

6. In radiation biology, the combination of physical & biological half-life creates an effective half life (Te) given by the formula ( 1 / Te  =  1/ Tp  +  1/Tb ) such that Te = (Tp)(Tb)/ (Tb + Tp)
                         Prove the formula. Then, calculate Te for 131I and 137Cs : show your work

6a. Using the banding data & densitometer plots in Fig.4 of Meselson & Stahl (1958), show the expected results for Experiment 1 if DNA replication were (a) Conservative or (b) Dispersive.

7. Which ONE of the following ssDNA strands is a Type-II restriction endonuclease site? Explain why it is, and why the others are not.

    (a) 5' - A A T T C G - 3'        (b) 5'- G G C C G G - 3'        (c) 5' - C G A T C G - 3'         (d) 5' - G A T C G A T C  - 3'     (e) 5' - A C G T T A C G T   - 3'

8.  Popular descriptions of automated DNA sequencing machines often state that "DNA sequences are read by a laser'" Is this true, or not true? Explain.

9.  The poly-UUU experiment is said to 'prove' that the Genetic Code is a triplet code. Is this true or not? Explain [ https://www.mun.ca/biology/scarr/Polynucleotide_phosphorylase.html ]

10. Show that a total of 16 codons in the Genetic Code can be inferred from RNA poly-monomers and poly-dimers of RNA.

11. Review this clip from the 1997 movie GATACCA as it relates to individual and societal implications of Pre-Implantation Genetic Diagnosis (PGD) in 2026.

(c) 2026, Steven M. Carr