DNA & PROTEIN SYNTHESIS (LIVE) 07 APRIL 2015 Section A: Summary Notes and Examples DNA Structure Each nucleic acid consists of a number of basic building blocks called nucleotides. Each nucleotide consists of three parts: 1 phosphate ion 1 pentose sugar This can be either a deoxyribose sugar (sugar without oxygen) or a ribose sugar 1 nitrogenous base Protein Synthesis Page 1
Section B: Practice Questions Question 1 (Taken from Learner Workbook, Mindset Learn, Chapter 1, Question 1, Pg 6) 1.1 The diagram below represents a part of a molecule. Study the diagram and answer the questions that follow. 1.1.1 Identify the molecule in the above diagram. (1) 1.1.2 Label the parts numbered 1 and 5 respectively. (2) 1.1.3 What is the collective name for the parts numbered 2, 3 and 4? (1) 1.1.4 What is the significance of this molecule being able to replicate itself? (2) Question 2 (Taken from Learner Workbook, Mindset Learn, Chapter 1, Question 2, Pg 7) 2.1 Where is DNA found? (2) 2.2 What are the constituent groups of molecules that form the nucleotides? (3) 2.3 Name the mrna produced by each of the following strands of DNA: a) A A C G G C T A T (1) b) C C G T A A C G A A T T (1) c) G C G A A T T C A (1) [8] Page 2
Question 3 (Taken from Learner Workbook, Mindset Learn, Chapter 1, Question 4, Pg 8) Study the diagram below and answer the questions that follow. (a) Identify this type of nucleic acid. (1) (b) Provide TWO visible reasons for your answer. (2) (c) Name the type of sugar represented by the letter S. (1) (d) Name two different types of the above molecule. (3) Question 4 (Taken from Learner Workbook, Mindset Learn, Chapter 1, Question 5, Pg 9) Tabulate THREE differences between DNA and RNA. (7) (Remember to give your table a suitable heading/caption. Compare the same characteristics for each of the columns.) Question 5 (Taken from Learner Workbook, Mindset Learn, Chapter 2, Question 1, Pg 13) Humans show differences in characteristics such as fingerprints. Humans have five main types of fingerprints as shown in the diagram below: (Hint: fingerprints and DNA fingerprints are not the same. You should know the difference) Page 3
A fingerprint is a useful way of identifying people and classifying them into groups. A fingerprint is taken by rolling the right index finger onto an ink pad and then onto a piece of paper. During a discussion of this topic, a group of learners asked the following question: ''Which one of the five main types of fingerprints is most common amongst the learners of this school?'' 5.1 State any FOUR steps in the planning process that must be considered when planning an investigation to answer the question above. (4) 5.2 The learners carried out an investigation and the results are shown in the table below. (a) Give a caption for the table. (2) (Remember that a caption is a heading where the words types of fingerprints and learners would have to be included since these are the headings of the two columns.) (b) Learners came to the following conclusion: Most learners have the plain arch-type fingerprint. Is this a valid conclusion? (1) (Remember that validity is based on the numbers, the accuracy and similar conditions like ages, males/females as applicable, etc) (c) Give a reason for your answer to QUESTION 5.2 (b). (2) 5.3 State the following: (a) (b) TWO advantages of having a fingerprint database of every citizen and visitor in South Africa. (2) TWO disadvantages of having a fingerprint database of every citizen and visitor in South Africa (2) Page 4
Question 6 (Taken from Learner Workbook, Mindset Learn, Chapter 2, Question 3, Pg 16) A child is born out of wedlock. The mother needs to claim maintenance for the child, but does not know which one of two men is the father. She has had blood tests done, but both the men have the same blood type. Her next alternative is to do DNA fingerprinting. Both men provide samples and the VNTR of both is analysed. The results are below. Identify the real father and explain how you reached your conclusion. (3) (Remember to use a ruler to check the corresponding VNTR codes) Question 7 (Taken from Learner Workbook, Mindset Learn, Chapter 4, Question 2, Pg 44) (Reminder: always complete the labels on a diagram before you move on to the questions) The following diagram represents protein synthesis: Page 5
7.1 Name the following processes: (a) A (1) (b) B (1) 7.2 Name the organelle labelled C. (1) 7.3 Explain how the mrna is made from the DNA template during process A. (5) (Reminder of transcription) 7.4 Processes A and B above can be summarised by the table below. Write the numbers 1 3 and next to each number the nitrogenous bases that will complete the table. (3) [11] HINT: Reminder: The DNA has a code. The mrna is always the opposite complimentary bases to the DNA, and the anticodons on the trna will always be the same as the DNA. Thymine on DNA is replaced with Uracil on the RNA) Question 8 (Taken from Learner Workbook, Mindset Learn, Chapter 4, Question 5, Pg 48) The diagram below represents a part of the process of protein synthesis. 8.1 Name or provide labels for N, P, Q, and Z (4) 8.2 Write down the sequence of the FIRST THREE nitrogenous bases on the DNA strand that led to the formation Z. (2) 8.3 Name the part / stage of protein synthesis that is illustrated in O. (1) The table below shows the base triplets of DNA and the amino acid each codes for: Page 6
8.4 With reference to the diagram and the table above: 8.4.1 Name the amino acid labelled P. (2) 8.4.2 State the base sequence of the molecule labelled Q. (2) 8.4.3 What name is given to the triplet of trna bases that codes for each amino acid. (1) 8.4.4 Describe how the composition of the protein molecule changes if the base sequence at X is UGU instead of UCA. (2) Question 9 (Taken from Learner Workbook, Mindset Learn, Chapter 4, Question 6, Pg 50) The table below shows the DNA base triplets that code for different amino acids. [14] The following is a part of a sequence of amino acids that form a particular protein molecule: 9.1 Name the process by which mrna is formed from a DNA template. (1) 9.2 How many mrna codons would be involved in forming the portion of protein shown above? (1) 9.3 Write down the sequence of the first THREE mrna codons (from left to right) for this portion of the protein. (3) 9.4 The following is a sequence of base triplets in DNA: GAA GTA TTT AAA 9.4.1 If guanine, found in the first base triplet, is removed, explain how this would affect the structure of the protein. (2) 9.4.2 Name the process that occurs when the sequence of bases in DNA changes. (1) [8] Question 10 (Taken from Learner Workbook, Mindset Learn, Chapter 4, Question 7, Pg 51) Describe the process of protein synthesis. [20] Page 7
Section C: Solutions Question 1 (Taken from Learner Workbook, Mindset Learn, Chapter 1, Question 1, Pg 6) 1.1.1 DNA (1) 1.1.2. 1 = Weak Hydrogen bond 5 = Cytosine (2) 1.1.3 Nucleotide (1) 1.1.4 DNA produces two exact copies of itself. / Allows chromosome to make copies of itself Question 2 Hereditary characteristics are passed on. ensures that each new cell has the same number of chromosomes to ensure that each cell in an organism has a complete and correct copy of the organism's genome, or "library" of genetic data ensures that any daughter cells produced will have a complete copy of the DNA necessary for the cell to survive. (2) (Taken from Learner Workbook, Mindset Learn, Chapter 1, Question 2, Pg 7) 2.1 nucleus some in mitochondria (1) 2.2 phophate ion, pentose sugar and nitrogenous base (1 mark each) (3) 2.3 a) U U G C C G A U A (1) Question 3 b) G G C A U U G C U U A A (1) c) C G C U U A A G U (1) (Taken from Learner Workbook, Mindset Learn, Chapter 1, Question 4, Pg 8) a) RNA (1) b) Single strand and uracil present (2) c) Ribose pentose sugar (1) d) Messenger RNA (mrna) and Transfer RNA (trna) (3) Question 4 (Taken from Learner Workbook, Mindset Learn, Chapter 1, Question 5, Pg 9) Table showing the differences between DNA and RNA. DNA Double strand Deoxyribose sugar Thymine RNA Single strand Ribose sugar Uracil Page 8
Question 5 (Taken from Learner Workbook, Mindset Learn, Chapter 2, Question 1, Pg 13) 5.1 Hypothesis formulation Sample selection Method of data collection Data representation Formulate hypothesis on what the most common type of fingerprint might be Identify dependent and independent variables Determine the sample size of learners to be used Learn how to identify the different fingerprint types correctly Organise an ink-pad and paper to take an imprint of the fingerprint Arrange a time and place to take fingerprints Design a table to record the number that have each fingerprint type (Mark first FOUR only) any (4) NOTE: Answers must be contexualised to the specific investigation on fingerprint types i.e. include if you will need to source equipment, determine date, a time and a venue 5.2 (a) (b) (c) Number of learners with different fingerprint types No Results indicate that most learners have the plain whorl type of fingerprinting any 2 OR Results indicate that learners with a plain arch type do not make up the largest number any 2 OR Results are not in line with the conclusion (2) (1) (2) 5.3 (a) Advantages Can be used to identify criminals lost children deceased bodies Immigration control can be more strict (Mark first TWO only) any (2) (b) Disadvantages Falsely incriminated/ (people can be framed) Infringing on the rights of people/invasion of privacy It is costly Incorrect capture of data/human error Not all personscan be fingerprinted e.g. amputees (Mark first TWO only) (2) Page 9
Question 6 (Taken from Learner Workbook, Mindset Learn, Chapter 2, Question 3, Pg 16) The father is 2. There are 5 matches in the VNTR. (3) Question 7 (Taken from Learner Workbook, Mindset Learn, Chapter 4, Question 2, Pg 44) 7.1 (a) A - Transcription (1) (Ensure that you know the definitions and processes for A and B) (b) B Translation (1) 7.2 C - Ribosome (1) 7.3 - Process is called transcription While DNA replication takes place Free (RNA) nucleotides from the nucleoplasm arrange according to the base sequence of the DNA template in a complementary way A U C G Sugar-phosphate bonds form between nucleotides to form required mrna Process controlled by enzymes max (5) 7.4 1 GUU 2 CAA Question 8 3 CGT (Taken from Learner Workbook, Mindset Learn, Chapter 4, Question 5, Pg 48) 8.1 N mrna P - amino acid Q- trna Z- codon (4) 8.2 A G T (2) 8.3 Transcription (1) 8.4.1 P - Threonine. (2) 8.4.2 Q C C G (2) 8.4.3 Anticodon (1) 8.4.4 Amino acid will change. It will be cytosine instead serine therefore the structure and function of the protein will change. (2) (3) Page 10
Question 9 (Taken from Learner Workbook, Mindset Learn, Chapter 4, Question 6, Pg 50) 9.1 Transcription (1) 9.2 5 (1) 9.3 G C U C A U U G G (3) 9.4.1 The amino acid will change and therefore the protein will be different. (2) 9.4.2 Mutation. (1) Question 10 (Taken from Learner Workbook, Mindset Learn, Chapter 4, Question 7, Pg 51) Protein synthesis - the process: The process of protein synthesis occurs in two steps, namely transcription and translation Transcription* Translation* Double stranded DNA unzips When the hydrogen bonds break One strand is used as a template To form mrna Using free RNA nucleotides from the nucleoplasm The coded message for protein synthesis is thus copied onto mrna mrna moves from the nucleus to the cytoplasm and attaches to the ribosome The mrna sequence is coded in segments of 3 called codons Max (*1+8) trna collects amino acids Each trna contains an anticodon specific to the amino acid it carries trnas, with amino acids attached, become arranged on the mrna The anticodons on the trnas match complementary bases on the codons of mrna Amino acids become attached by peptide bonds to form the required protein Each trna is released to pick up more amino acids Synthesis Max (*1+7) (3marks) Page 11