Exam 2011, questions PDF

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Student ID:_______________________ Last Name:_______________________ First Name:_______________________ Primary Examination

Desk & Row:______________________ Date:____________________________

Semester 1, 2011 102281

BIOLOGY 1: Molecules, Genes & Cells BIOLOGY 1101 & BIOLOGY 1101BR BIOLOGY 1: Molecules Genes Cells (Pre-Vet)

104263

BIOLOGY 1510 Official Reading Time: Writing Time: Total Duration: Section A B C

10 mins 180 mins 190 mins

Marks 30 marks (answer all questions) 30 marks (answer 2 only of the 4 alternatives) 90 marks (answer all questions on the sheet provided)

Instructions • •

• • •

Write your name, Student ID, row and letter number and date in the top right hand corner of this page. Write the answers for Sections A & B in this booklet in the spaces provided. If you need additional space you may write on the reverse side of the sheet, but ensure that you clearly indicate that you have done this. Use labelled diagrams if appropriate Examination materials must not be removed from the examination room. Please use pencil to complete Section C on the separate answer sheet provided. Any mistakes should be erased and NOT crossed out.

Materials • • • •

Question Paper Answer Book MCQ Question Book MCQ answer sheet Non-programmable alphanumeric calculators ARE permitted

DO NOT COMMENCE WRITING UNTIL INSTRUCTED TO DO SO For marking use only TOTAL

SECTION

A

1

2

3

B

6A

6B

6C

4

/30

5

/30

6D

C

/90 Total

/150

MARKER

Page 2 of 14 Biology 1101 and Biology 1510

SECTION A (30 marks) QUESTION 1 (6 marks total) a)

On the diagram of ATP shown below: (i) Draw a circle around the nitrogenous base portion. (ii) Draw a circle around the nucleoside portion. (iii) ATP is incorporated into RNA and deoxy-ATP is incorporated into DNA. Draw an arrow pointing to the atom that is different between ATP and deoxy-ATP.

b)

On the diagram of the short tri-peptide glu-lys-leu shown below: (i) draw a circle around the side chain of lysine (ii) draw an arrow pointing to a peptide bond (iii) draw a circle around the amino acid residue glutamate.

Page 3 of 14 Biology 1101 and Biology 1510

QUESTION 2 (6 marks total) Give a brief outline of TWO of the following processes, stating I. what happens II. why it happens III. where in the cell it happens a) Glycolysis

b) Calvin cycle

c) Citric Acid cycle

Page 4 of 14 Biology 1101 and Biology 1510

QUESTION 3 (2 marks total) a) How does allosteric inhibition of enzyme activity differ from competitive inhibition? (1 mark)

b) List 2 factors that affect enzyme activity. (1 mark)

QUESTION 4 (6 marks total) Illustrate how DNA replication occurs in Escherichia coli by drawing a diagram of the events occurring at a replication fork (6 marks)

Page 5 of 14 Biology 1101 and Biology 1510

QUESTION 5 (10 marks total) T. H. Morgan test crossed F1 flies derived from a cross between a pure breeding wild type parent with grey body and normal wings (b+ b+, vg+ vg+) and pure breeding parent with black body and vestigial wings (b b, vg vg). The wild type alleles are dominant. The phenotypes of the test cross progeny contained the following numbers of flies: Grey body, normal wings Grey body, vestigial wings Black body, normal wings Black body, vestigial wings Total number of flies

906 102 98 894 2000

(i)

Give the genotypes of the progeny recovered in the test cross.

(2 marks)

(ii)

What would be the expected phenotypic ratios in the 2000 test cross progeny if the two genes were independently assorting? (2 marks)

(iii)

How many map units (centiMorgans, cM) separate the black body and vestigial wing loci? Show your working. (2 marks)

(iv)

Using ONLY labelled diagrams involving a meiotic bivalent, show how both recombinant and parental gametes may be produced from a single meiosis (4 marks)

Page 6 of 14 Biology 1101 and Biology 1510

SECTION B (30 marks) Answer 2 (TWO) ONLY of the Following 4 (FOUR) Alternatives QUESTION 6 – ALTERNATIVE A (15 marks total) All living organisms with a cellular organisation use DNA as their genetic material. a) Describe how Meselson and Stahl were able to prove that DNA replication was semiconservative rather than conservative or dispersive in nature. Your answer should include a brief outline of what they did, the results they observed and the conclusions they were able to draw. (6 marks)

Page 7 of 14 Biology 1101 and Biology 1510

b) Thermus aquaticus, a thermophile, is able to live at temperatures in excess of 90°C.Their DNA has a G+C ratio of 68%. i)

Determine the overall nitrogenous base composition of T aquaticus. (2 marks)

ii)

How does this high G+C value account for its ability to live at very high temperatures? (2 marks)

c) The Central Dogma states that information flow in a cell is DNA → RNA → Protein. Give two reasons why it is advantageous to use an RNA intermediate to form protein. (2 marks)

d) Why does DNA Polymerase III have proof reading capacity but RNA Polymerase does not? (3 marks)

Page 8 of 14 Biology 1101 and Biology 1510

QUESTION 6 – ALTERNATIVE B (15 marks total) Cystic fibrosis is the most common genetic disorder in western societies. The condition results from mutation of the CFTR gene. a) The gene, located on chromosome 7, is approximately 250kb in length. However the mature mRNA that exits the nucleus is only 6.5kb in length. Explain why there is this difference in size. (2 marks)

b) The most common mutation seen, accounting for 70% of all cystic fibrosis, involves two codons and results in a so-called “indel” mutation denoted ∆F508, which leads to the loss of a phenylalanine amino acid. i.

Why are some mutations regarded as silent?

(2 marks)

ii. To which class of amino acid does phenylalanine belong?. (1 mark)

c) The pedigree below shows a family where cystic fibrosis is found.

Page 9 of 14 Biology 1101 and Biology 1510

i.

Does this pedigree indicate a dominant or recessive mode of inheritance? Explain. (2 marks)

ii. Using the gene symbols A,a , indicate the genotypes of all individuals in this pedigree. (3 marks) Genotype

Genotype

I1

II 1

I2

II 2 II 3 II 4

d) The CFTR gene encodes a trans-membrane protein. How does the folding of membrane proteins differ from proteins found in the cytosol? (2 marks)

e) Given that the protein encoded by the CFTR gene regulates Cl− efflux from the cell, explain why people with cystic fibrosis have very thick, sticky (viscous) mucous. (3 marks)

Page 10 of 14 Biology 1101 and Biology 1510

QUESTION 6 – ALTERNATIVE C (15 marks total) Some haemophilia B suffers carry pathogenic mutations in the gene encoding the factor IX protein. The nucleotide sequence shown below corresponds to a segment of the nontranscribed (or coding) strand of the gene. Non-affected individual: 5’ A G A G T T C C A C T T G T T G A C C G A G C C A C A T G T 3’ Individual with haemophilia B: 5’ A G A G T T C C A C T T G A C C G A G C C A C A T G T 3’

(a) Write down the mRNA transcribed from each DNA segment

(2 marks)

(b) Using the genetic code shown in the table below, show the amino acid sequence in this region of the factor IX protein for the non-affected and affected individuals. Assume that the first base shown in the sequence is the first nucleotide of a codon (3 marks)

Page 11 of 14 Biology 1101 and Biology 1510

(c) What are the effects of this mutation on the factor IX protein?

( 1 mark mark))

(d) The sequence of the gene in the region of the mutation is shown below, and the bases deleted in the pathogenic mutation are boxed.

5’AGCAAAAGCG AAATGTGATT CGAATTATTC CTCACCACAA CTACAATGCA GCTATTAATA AGTACAACCA TGACATTGCC CTTCTGGAAC TGGACGAACC CTTAGTGCTA AACAGCTACG TTACACCTAT TTGCATTGCT GACAAGGAAT ACACGAACAT CTTCCTCAAA TTTGGATCTG GCTATGTAAG TGGCTGGGGA AGAGTCTTCC ACAAAGGGAG ATCAGCTTTA GTTCTTCAGT ACCTTAGAGT TCCACTTGTT GACCGAGCCA CATGTCTTCG ATCTACAAAG TTCACCATCT ATAACAACAT GTTCTGTGCT GGCTTCCATG AAGGAGGTAG AGATTCATGT CAAGGAGATA GTGGGGGACC CCATGTTACT GAAGTGGAAG GGACCAGTTT CTTAACTGGA ATTATTAGCT GGGGTGAAGA GTGTGCAATG AAAGGCAAAT ATGGAATATA TACCAAGGTA TCCCGGTATG TCAACTGGAT TAAGGAAAAA ACAAAGCTCA CTTAATGAAA GATGGATTTC CAAGGTTAAT TCATTGGAAT TGAAAATTAA CAGGGCCTCT CACTAACTAA TCACTTTCCC ATCTTTTGTT 3’

Write down the sequence of two primers [each 16 nucleotides long] that can be used in a polymerase chain reaction [PCR] to amplify this whole region of DNA. (4 marks)

Page 12 of 14 Biology 1101 and Biology 1510

(e) Factor IX plays a key role in blood clotting (coagulation). Factor IX is a glycoprotein that displays quaternary structure, and is comprised of two chains held together by a disulphide bond. Each chain is comprised of four domains; the carboxy terminal domain contains the protease activity. Given this information answer the following questions (1 mark each, 5 marks total) i)

With respect to proteins, what is meant by the term quaternary structure?

ii)

Where in the cell does glycosylation occur?

iii)

Which amino acid forms disulphide bonds?

iv)

With respect to proteins, what does the term domain mean?

v)

What do proteases do?

Page 13 of 14 Biology 1101 and Biology 1510

QUESTION 6 – ALTERNATIVE D (15 marks total) a) Draw and label the main structural features of a mitochondrion and a chloroplast. (6 marks)

b) Theory suggests that in plants, the acquisition of chloroplasts and mitochondria occurred independently. Explain which must have come first and why. (3 marks)

Page 14 of 14 Biology 1101 and Biology 1510

c) Compare and contrast (mechanism, energy source etc) of the three systems of ATP production: (6 marks total) i)

Substrate-level phosphorylation

ii) Oxidative phosphorylation

iii) Photophosphorylation

Questions for Section C are in a separate book...