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PLEDGE: I neither gave nor received help on this exam. SIGNED:

Please read ALL questions CAREFULLY before starting. Answer in as short a manner as possible--writing down a lot of words won't necessarily help.

1. (3 pts.) Point mutations in a gene can lead to three types of effects on the encoded protein. What are these effects?

2. (12 pts.) Using the four DNA bases (A, T, C, and G) list the possible point mutations that are:

A) Transitions:

B) Transversions:

3. (12 pts.) In Müller's classic ClB technique for detection of mutations in Drosophila:

A) What type of mutation can be detected?

B) What is the importance of the l gene in the technique?

C) Why is it necessary to have the crossover suppressor (C) in the technique?

D) What is nature of the C mutation?

4. (4 pts.) A transposon needs two features to ensure its successful transposition. What are they and what does each do?

5. (10 pts.) For the following genotypes and conditions (+ or - lactose), predict with a checkmark in the correct column, whether functional, non-functional, or no enzymes are made:

Genotype			Lactose?	Functional Non-functional No enzyme?
                             			enzyme?	   enzyme?

I+ O+ Z+                            -

I+ OC Z+                            +

I- O+ Z-                            -

I- O+ Z-                            +

I- O+ Z+  / F'I+                    -

I+ OC Z+  / F'O+                    +

I+ O+ Z-  / F'I+ O+ Z+              +

I- O+ Z-  / F' I+ O+ Z+             -

IS O+ Z+  / F' O+                   -

I+ OC Z+ / F' O+ Z+                 +

6. (4 pts.) Many bacterial operons are regulated in part by the CAP-cAMP complex.

A) What controls formation of this complex during regulation of the lac and ara operons?

B) Once formed, what type of regulation does this complex exhibit?

7. (6 pts.) The model genetic plant Arabidopsis thaliana consists of 2 x 10⁸ base pairs of DNA per nuclues. If this DNA is packaged as chromatin where each 200 base pairs of DNA is combined with 9 histones into a nucleosome, and each group of 5 nucleosomes is combined into a solenoid with a packing ratio of 50 then determine:

A) The total number of nucleosomes per nucleus.

B) The total number of solenoids per nucleus.

C) The total number of histone molecules combined with DNA per nucleus.

8. (4 pts) DNA elements which function as transcriptional promoters for eukaryotic genes can be quite complex.

A) What are the key protein components which assemble on a eukaryotic "core" promoter?

B) How do typical eukaryotic enhancer DNA elements function differently from typical eukaryotic "core" promoter DNA elements?

9. (18 pts.) The tryptophan (trp) operon is controlled at various levels.

A) When free tryptophan levels are high in a bacterium, how is transcription of the trp operon regulated?

B) When free tryptophan is low, but charged tRNA-trp is still present, how is transcription regulated?

This is a diagram of some of the key components of the trp attenuator region:

C) Using this diagram as a base, draw the situation reflected in part (B).

D) Again using the basic diagram, draw the situation when charged tRNA-trp levels are very low, or absent.

E) What is the end outcome of the situation you drew in (D)?

F) What is the outcome of a mutation in Region 2 of the basic diagram which prevents it from participating in a stem-loop (hairpin) structure and what is the phenotype of the mutant?

10. (6 pts.) List 6 levels of control of eukaryotic gene regulation that can be influence the generation of a functional protein.

11. (12 pts.) The drawing below depicts a typical signal transduction cascade from ligand binding (1), receptor dimerization and activation of receptor kinase activity (2), through kinase activation of a signaling protein (3), to phosphorylation of a complex containing a transcription factor (4), which ends up in localization of the transcription factor to the nucleus (5), where it acts to turn on genes involved in cell division (6). Propose and explain how three different mutations in steps along this pathway would lead to constitutive (always on) transcription of the cell division genes and, potentially, oncogenesis.

12. (9 pts.) The Rb gene is involved in tumor formation in the retina.

A) What is the probable genomic status of the Rb (Retinoblastoma) gene in a patient with Retinoblastoma tumors in BOTH eyes compared to a patient with a tumor in one eye?

B). And which patient's children could inherit a genetic predisposition to developing Retinoblastoma?