Biology 12 DNA Functions Practice Exam - KEY A. DNA Structure 1. DNA is often called the "code of life". Actually it contains the code for a) the sequence of amino acids in a protein b) the sequence of base pairs c) producing mutations d) making a recipe Name: 2. Describe (draw) the structure of a chromosome. Identify: DNA, proteins + a gene. 3. One nucleotide of DNA is made of three smaller parts. What are these parts? Phosphate Deoxyribose sugar Nitrogenous base 4. What are the full names of the bases found in DNA? Which ones bond with each other? Adenine, Cytosine, Guanine, Thymine 5. Fill in the following chart that compares DNA and RNA: DNA RNA # of strands two one type of sugar Deoxyribose sugar Ribose sugar location in cell nucleus Nucleus + cytoplasm (ribosome) bases A, T, C, G A, U, C, G types DNA mrna, trna, rrna 6. A sample of DNA was analyzed and scientists found that 32% of the nitrogenous bases were guanine. What percentage of the following bases would also be in the sample? Thymine: 18% Cytosine: 32% Uracil: 0% Adenine: 18%
B. DNA Replication 7. a. What is the result of DNA replication? Exact copies of DNA (chromosomes) b. Where in the cell does DNA replication occur? Cell division occurs in the nucleus c. Why does DNA replication occur before cell division? So that new cells can receive an exact copy of DNA d. Why is cell division an important cell process? To replace dead cells and for growth and repair 8. a) Name the molecule indicated by X. DNA b) Where in a human cell does the process shown above occur? Nucleus c) List three functions of molecule X. 1. replication 2. Protein synthesis 3. mutation
Protein Synthesis 9. Give one role of each of the following in the production of a protein. a. DNA - carries the code to produce a polypeptide or carries the code to produce mrna. b. mrna - carries the DNA code out of the nucleus to the ribosome c. trna - brings amino acids to the ribosome (to the mrna) d. rrna - with proteins forms the ribosome (ribosome is the site of protein synthesis) 10. Reading from left to right, from the DNA sequence: T A C A A G A T T a. What is the importance of the codon transcribed at the end of this sequence? (1 mark) U A A is a stop codon b. What would be the corresponding trna bases found on the anticodons? (1 mark) mrna: A U G U U C U A A trna: U A C A A G A U U c. Which amino acids would be coded for if cytosine was deleted from the DNA sequence? 1 mrna: A U U U C U A A Amino acids: isoleucine serine
11. Complete the following chart contrasting the two parts of protein synthesis: Transcription Translation Location in cell where it occurs nucleus Cytoplasm (ribosome) Types of RNA associated with this mrna mrna, trna, rrna Product mrna Polypeptide (potein) 12. What is the name of the structure that a) Carries amino acids to the ribosome? trna b) Forms between adjacent amino acids? Peptide bond c) Is the original instructions for a protein? DNA d) Contains a series of codons? mrna e) Is the site of translation? Ribosome 13. Use the following DNA sequence to answer the questions below: T A A C C G G A T A G T C T A A T T a) What is the mrna sequence that would be transcribed from the DNA above? A U U G G C C U A U C A G A U U A A b) Use your chart of mrna codons to list the 6 amino acids in the sequence. Isoleucine glycine leucine serine aspartic acid - stop c) What type of bond would join these amino acids together? Peptide bond d) What would be the sequence of bases (letters) on the trna anticodons that would bring the above amino acids to the ribosome? U A A C C G G A U A G U C U A A U U 14. How many amino acids will be in a polypeptide with the following DNA sequence: ATT GCC ATG ACA ATA GGC ATA AAC AGG TCA mrna: UAA CGG UAC UGU UAU CCG UAU UUG UCC AGU Amino acids: stop 0 amino acids 15. Which of the following best describes the function of mrna? a) it stays in the nucleus and is copied by DNA b) it carries amino acids to the growing polypeptide chain c) it makes up the ribosomes and provides the site for protein synthesis d) it is transcribed from the DNA and carries the information to the ribosome
16. Read the following DNA sequence left to right: T A T C T T a. What will be the correct mrna sequence? AUA GAA b. What will be the correct amino acid sequence? Isoleucine Glutamic acid 17. Using the table of codons, determine the sequence of amino acids coded for by this mrna sequence: C - U - C - C - G - A - U - A - C Amino acid sequence: leucine arginine - tryosine 18. The role of ribosomes in protein synthesis is to a) split the two strands of DNA apart. b) check for and replace faulty codons. c) carry amino acids to the site of translation. d) provide a site for mrna and trna to join together. 19. What is the DNA sequence that would produce the following amino acid strand: alanine methionine alanine a) G C A A U G G C G b) G C G A U G C G C c) C G G T A C C G A d) C G C T A G G C A 20. The following is a sequence of mrna bases: G CU U C U C CU What sequence of amino acids results after translation occurs? Alanine serine - proline 21. Consider the following portion of an mrna strand: UAC GGG AUA What are the anticodons that will be paired to this strand? a) AT G CCC TAT b) AT A GGG TAC c) AUG CCC UAU d) UAC GGG AUA 22. Complete the following chart comparing DNA replication and protein synthesis: DNA replication Protein synthesis Location where it occurs nucleus Nucleus and ribosome Product Exact copy of DNA Protein (amino acid sequence) Types of nucleic acids used during this process DNA DNA, mrna, trna, rrna
C. Mutation 23. The DNA strand C GA T G C G A C A T T undergoes a mutation in which the section coding for the amino acid threonine is lost. Which of the following would be the correct codons after this mutation? a) A C G C U G U AA b) G C U A C G C UG c) G C U C U G U AA d) G C U A C G U AA 24. Give an explanation for how the following occurs: a) Sometimes a change of one nucleotide in a gene can result in a different polypeptide. A mutation changes the mrna and therefore the amino acid sequence. b) Sometimes a change of one nucleotide in gene will not result in a different polypeptide. A mutation that changes AAA to AAG still codes for lysine c) Use the genetic code to give a specific example. A mutation that changes AAA to AAG still codes for lysine 25. An investigation was carried out to examine the probable effects of addition and substitution mutations. A diagram of a section of DNA is shown: C A T G G T T A C G T A C C A A T G The bold strand reading from left to right is the one used to produce a polypeptide. Use the table of mrna codons to determine your answers. a) Give the sequence of bases on the mrna and the resulting sequence of amino acids produced. mrna: C A U G G U U A C amino acids: histidine glycine tryosine b) If a third cytosine (C) is added between the two already found in the bold strand of the original DNA, give the sequences on the mrna and the resulting sequence of amino acids produced. mutated DNA: G T A C C C A A T G mutated RNA: C A U G G G U U A C amino acid sequence: histidine glycine leucine c) If the guanine (G) at the start of the original DNA strand is deleted, give the sequences on the mrna and the resulting sequence of amino acids produced. mutated DNA: T A C C A A T G mutated RNA: A U G G U U A C amino acid sequence: methionine valine d) Explain which of the mutations described in parts b and c would result in the greatest change in the structure of the original polypeptide. The 2nd mutation has the greatest effect on the polypeptide being formed. e) List 2 environmental mutagens which could cause the changes described in parts b & c. X rays UV light Tobacco smoke Chemicals Viruses