Name: Teacher: Score: /30 Unit 1 Cell Biology Key Area 4: DNA and Production of Proteins (Q1-5 are multiple choice, choose ONE answer by clearly writing/circling ONE letter. Each question is worth one mark) 1. All proteins are composed of A genes B DNA C amino acids D bases. 3. The diagram below shows parts of an animal cell. 2. A section of a DNA molecule contains 300 bases. Of these bases, 90 are adenine. How many cytosine bases would this section of DNA contain? A 60 B 90 C 120 D 180 Where does synthesis of protein take place? 4. On the above diagram which letter indicates the site of mrna synthesis? (space for working) 5. The diagram below represents the chemical structure of the protein ADH. Which line in the table below identifies X and Y correctly? X Y A hydrogen bond base B hydrogen bond amino acid C peptide bond base D peptide bond amino acid 1
6. (a) The diagram below shows a yeast cell. (i) Name the structure shown in the yeast cell which contains the genetic information. (ii) A molecule consisting of chains of bases is contained in chromosomes. (A) Name this molecule. (B) Explain how this molecule controls cell activities. (2) (b) The sentence below describes the function of DNA. Underline one option in each set of brackets to make the following sentence correct. (2) 2
7. (a) Decide if each of the following statements about DNA and Protein synthesis is True or False and tick ( ) the appropriate box. If the statement is False, write the correct word in the correction box to replace the word underlined in the statement. Statement True False Correction During protein synthesis mrna moves from the nucleus to a ribosome. In RNA the base thymine is replaced with guanine. Peptide bonds form between complementary bases in a DNA molecule. (2) (b) A single strand of a DNA molecule has 6000 nucleotides of which 24% are adenine and 18% are cytosine. (i) Calculate the combined percentage of thymine and guanine bases on the same DNA strand. Space for calculation Answer % (ii) How many guanine bases would be present on the complementary strand of this DNA molecule? Space for calculation Answer bases (c) A piece of DNA consisted of 74 base pairs. The two strands of the DNA, strands A and B, were analysed to find the number of bases of each type that were present. Some of the results are shown in the table. Complete the table by writing in the missing values. 3
8. The table shows the base sequences of some mrna codons and the amino acids for which they code. (a) (i) State the mrna codon for methionine. (ii) Use information from the table to identify the common feature of all mrna codons which code for the amino acid arginine.. (b) Complete the diagram below by naming the two amino acids corresponding to the bases on the strand of DNA shown. 4
9. The diagram shows a stage in the synthesis of a protein. (a) Complete the diagram below by adding the appropriate letters to show the sequence of nine bases on the DNA strand from which the mrna strand shown has been transcribed. (b) Name organelle Z. (c) How many amino acids would the sequence AUGUAGUAC code for? (d) Name bond Y. 5
10. Ribonuclease is a protein 127 amino acids long. What is the minimum number of DNA bases needed to code for ribonuclease? Figure 2 shows the sequence of DNA bases coding for seven amino acids in the enzyme ribonuclease. Figure 2 G T T T A C T A C T C T T C T T C T T T A The number of each type of amino acid coded for by this sequence of DNA bases is shown in the table. Amino Acid Number Present Arg 3 Met 2 Gln 1 Asn 1 Use the table and Figure 2 to work out the sequence of amino acids in this part of the enzyme. Write your answer in the boxes below. 11. Write short notes to describe the differences between DNA and RNA (5) 6