Biological Functions of Nucleic Acids - UNSOLVED PRACTICE SET

Q7. What is replication? Why is it called semi-conservative?

Q8. Distinguish between transcription and translation. Where does each process occur in the cell?

Q9. What is the genetic code? State two important characteristics of the genetic code.

Q10. What is the role of tRNA in protein synthesis? What is meant by the "anticodon" of tRNA?

Q11. Why is DNA called the "molecule of heredity"? What property of DNA makes it suitable for this role?

Q12. What is a gene mutation? Give one example of how a mutation can affect protein function.

Q13. (a) Describe the process of DNA replication. Why is it called semi-conservative?

(b) Explain the roles of the following enzymes in replication:

(i) DNA helicase

(ii) DNA polymerase

(iii) DNA ligase

(c) What would happen if DNA replication were conservative instead of semi-conservative?

Q14. (a) Describe the central dogma of molecular biology. Draw a flow diagram showing the flow of genetic information.

(b) Explain the process of transcription in detail. What are the three types of RNA produced, and what are their functions?

(c) How does the genetic code ensure that the correct amino acid is inserted during translation?

Q15. (a) Describe the process of translation (protein synthesis) in a step-by-step manner. Include the roles of:

- mRNA

- tRNA

- Ribosomes

- Amino acids

(b) What is meant by "degeneracy" of the genetic code? How is this property advantageous?

Q16. A gene contains 1200 base pairs.

(a) How many nucleotides does this gene contain?

(b) During transcription, an mRNA is synthesized. How many nucleotides will the mRNA contain? (Assume no introns.)

(c) How many codons will this mRNA have?

(d) How many amino acids will be present in the protein synthesized from this mRNA? (Assume one start codon and one stop codon.)

(e) If a mutation changes one base pair in the middle of the gene, what are the possible effects on the protein? (Consider silent, missense, and nonsense mutations.)

Q17. The following table shows the genetic code (mRNA codons) for some amino acids:

(a) An mRNA has the sequence: 5'-AUG-UUU-CUG-UAU-UGG-UGA-3'. How many amino acids will be in the resulting protein? Write the sequence using three-letter abbreviations.

(b) If the third codon (CUG) is changed to CUC, does the amino acid change? What property of the genetic code does this demonstrate?

(c) If the fifth codon (UGG) is changed to UGA, what happens? What type of mutation is this?

(d) The start codon AUG codes for methionine. Is methionine always present at the N-terminus of all proteins in the cell? Explain.

(e) A scientist wants to synthesize a protein with 100 amino acids. What is the minimum number of nucleotides required in the gene? (Include start and stop codons.)

Q18. In a school biotechnology workshop, students learn about DNA fingerprinting and genetic testing.

(a) What is DNA fingerprinting? On what principle is it based?

(b) Why is DNA fingerprinting used in criminal investigations and paternity testing?

(c) A child has blood type AB. The mother has blood type A and the alleged father has blood type B. Can DNA fingerprinting confirm paternity more accurately than blood typing? Explain why.

(d) The students extract DNA from their own cheek cells using a simple salt and detergent method. Why does detergent break open the cell membrane? Why is cold alcohol added at the end?

(e) Polymerase Chain Reaction (PCR) is used to amplify small amounts of DNA. If you start with 1 DNA molecule, how many molecules will you have after 30 cycles of PCR? What does this tell you about the power of this technique?