NAME:______________________________________________ Fall 2005 TF:______________________________________________________

Biological Sciences 50 Practice Exam 2

A. Be sure to write your name on the top of each of page of the examination.

B. Write each answer only on the same page as the pertinent question. THE SPACE PROVIDED IS MEANT TO BE SUFFICIENT; BE BRIEF, BE CAREFUL, BE CONCISE! If absolutely necessary, use the back of that page to continue the answer.

C. IF YOUR ANSWER CANNOT BE READ IT CANNOT BE GRADED!!!

D. Remember, if you do not show all your work, you cannot get partial credit.

E. The point value for each question is noted.

Allocate your time wisely.

F. Read carefully, think before you write, good luck, and do well!

IF YOU WRITE IN PENCIL, YOU CANNOT ASK FOR A REGRADE! Question 1: __________ (9 pts) Question 2: __________ (11 pts) Question 3: __________ (18 pts) Question 4: __________ (16 pts) Question 5: __________ (22 pts) Question 6: __________ (24 pts)

TOTAL: _______ (100 pts)

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Question 1 (9 points). a) Does the molecular below come from RNA or DNA? Justify your answer.

b) List two other structural differences between RNA and DNA Question 2 (11 points) The following table contains a list of statements that apply to replication, transcription, both, or neither. In each empty box, put a check mark if that statement applies to replication or transcription.

Replication Transcription In eukaryotes, the process occurs in the nucleus. A primer is required to initiate synthesis. The polymerase moves 5’ to 3’ along the template strand. The polymerase moves 3’ to 5’ along the template strand. The process requires DNA unwinding The product is DNA. The product is RNA. The template is used only once per cell cycle Synthesis of the new strand is initiated at a promoter. The product may be modified after synthesis Proof-reading and repair are incorporated into this process.

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Question 3 (18 points). The line below represents a prokaryotic gene. The rectangle represents the coding region. Below the DNA diagram, draw the corresponding RNA (roughly to scale) and polypeptide. Where appropriate, indicate the location of the following:

start codon polyA tail 3’UTR hairpin loop 5’ cap amino terminal stop codon carboxy terminal 5’ UTR promoter methionine (met) intron

coding region DNA

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Question 4 (16 points). You are studying an inversion heterozygote. The order of genes along one homolog is centromere – A – B – D – E – F The order of genes along the other homolog is centromere – A – E – D – B – F a) Assuming that the first homolog is the normal chromosome, draw an arrow(s) at that breakpoint(s) that gave rise to the abnormal chromosome b) The homologs undergo recombination between genes B and D. Draw a clear sketch depicting the chromosomes of this inversion heterozygote as they align at pachytene. In your sketch, only include the chromatids undergoing recombination. c) Draw a clear sketch of the recombinant products from such as cross-over event. d) Will the recombinant chromatids segregate normally during cell division? Explain.

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Question 5 (22 points). You are studying a gene in E. coli that specifies a protein enzyme. Part of the wild-type sequence is given below. You recover a series of mutants for this gene that show no enzyme activity. Isolating and sequencing the mutant products, you find the following protein sequences (assume each mutant is the result of a single nucleotide change):

Wild-type: - Met - Cys – Ala - Gln - Ile – Tyr –

Mutant 1: - Met - Cys – Ala - Gln - Thr – Tyr – Mutant 2: - Met - Cys – Ala Mutant 3: - Met - Val – Pro – Arg – Phe - Thr

a) How may different mRNA sequences could code for this portion of the wild-type protein? Show your work. b) For the FIRST amino acid affected by each mutation, give the original codon(s) and the mutant codon(s) as specifically as possible. Use all the data and show your work. Clearly indicate the type of mutation that has occurred.

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Question 6 (24 pts) The following is a list of mutational changes. For each of the specific changes described, indicate which of the terms listed below could apply, either as a description of the mutation or as a possible cause. More than one term from the list can apply to each and individual terms may be used once, more than once, or not at all. a) a G-C base pair is changed to an A-T base pair b) a G-C base pair is changed to a T-A base pair c) the sequence AAGCTTATCG is changed to AACTTATCG d) the sequence AACGTCACACATCG is changed to AACGTCACACACACATCG transition base substitution transversion inversion indel deamination intercalating agent frameshift replication slippage SOS system photodimer Optional (check one answer for each question) This exam was ____________ too short ____________ too long ____________ about right This exam was ____________ too easy ____________ too hard ____________ about right Write brief additional comments about the exam (or the course so far) below: