Question 1: Define a nucleotide and explain its role in DNA structure.

Answer: A nucleotide is the basic unit of DNA, consisting of a sugar, phosphate group, and nitrogenous base; it forms the building blocks of DNA strands and stores genetic information.

Question 2: Describe the primary structure of an amino acid and how amino acids link to form proteins.

Answer: An amino acid has a central carbon atom bonded to an amino group, a carboxyl group, a hydrogen atom, and a variable R group. Amino acids link via peptide bonds in a specific sequence to form proteins.

Question 3: What is the significance of the sequence of bases in DNA?

Answer: The sequence of bases determines the genetic code, which directs the synthesis of specific proteins in an organism.

Question 4: Explain how amino acids are involved in the synthesis of enzymes.

Answer: Amino acids are the building blocks of enzymes; their specific sequence determines the enzyme's structure and function, enabling it to catalyse biological reactions.

Question 1: Calculate the number of nucleotides in a DNA molecule that has a mass of 3.3 x 10^-12 grams. (Molecular weight of a nucleotide approx. 330 g/mol)

Answer: Number of nucleotides = (Mass of DNA / Molecular weight of one nucleotide) x Avogadro's number. Number of nucleotides = (3.3 x 10^-12 g / 330 g/mol) x 6.022 x 10^23 mol^-1 ≈ 6.02 x 10^9 nucleotides.

Question 2: If a protein contains 150 amino acids, what is its approximate molecular weight? (Average weight of an amino acid = 110 g/mol)

Answer: Molecular weight = Number of amino acids x weight per amino acid = 150 x 110 g/mol = 16,500 g/mol.

Question 1: Describe a simple experiment to extract DNA from fruit tissue. Include key variables and safety precautions.

Answer: To extract DNA from fruit, mash the fruit and mix with a solution of detergent and salt to break cell membranes and clump DNA. Variables include temperature, pH, and amount of detergent. Safety precautions involve wearing gloves and goggles to handle chemicals and avoid ingestion.

Question 2: Identify the independent and dependent variables in an experiment testing the effect of pH on amino acid solubility.

Answer: Independent variable: pH of the solution. Dependent variable: solubility of amino acids.

Question 1: A sample of DNA was analysed and found to contain 30% adenine. What percentage of thymine is expected, and why?

Answer: Thymine will also be 30% because of complementary base pairing in DNA (A pairs with T).

Question 2: In a protein, 20% of the amino acids are leucine. If the protein has 200 amino acids, how many leucine residues are present?

Answer: Number of leucine residues = 20% of 200 = 0.20 x 200 = 40 leucine residues.

Question 1: Explain how mutations in the DNA sequence can affect protein synthesis.

Answer: Mutations alter the sequence of bases in DNA, which can lead to changes in the mRNA transcribed. This can result in the incorporation of different amino acids during protein synthesis, potentially affecting the protein's structure and function.

Question 2: Describe how amino acids with different R groups influence the properties of a protein.

Answer: Amino acids with different R groups impart unique properties such as polarity, charge, and size, which influence the folding, stability, and function of the protein.

Question 3: Identify a real-world application of DNA technology in industry or medicine and briefly explain its significance.

Answer: DNA technology is used in genetic engineering, such as producing insulin through bacteria. This allows for large-scale, cost-effective production of medical treatments, improving healthcare outcomes.