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

Answer: A nucleotide is the basic building block of DNA, consisting of a sugar, a phosphate group, and a nitrogenous base; it forms the genetic code and links together to form the DNA double helix.

Question 2: Explain how amino acids are linked together to form proteins.

Answer: Amino acids are linked by peptide bonds through condensation reactions, forming polypeptides that fold into functional proteins.

Question 1: Calculate the number of amino acids in a protein with a molecular weight of 50,000 g/mol, given that the average weight of an amino acid residue is 110 g/mol.

Answer: Number of amino acids = 50,000 g/mol ÷ 110 g/mol ≈ 455 amino acids.

Question 2: A DNA sample contains 30% adenine. What is the percentage of cytosine in this DNA? (Assuming Chargaff's rules apply.)

Answer: Cytosine makes up 20% of the DNA, since adenine pairs with thymine and cytosine pairs with guanine, so A = T = 30%, G = C = 20%.

Question 1: Describe a safe method to extract amino acids from a protein sample in a laboratory setting.

Answer: Use a suitable solvent like hydrochloric acid to hydrolyse the protein, wear protective gloves and goggles, work in a fume cupboard, and dispose of chemicals safely afterwards.

Question 2: Identify two variables that could affect the efficiency of DNA extraction in an experiment.

Answer: Variables include the temperature during extraction and the type or purity of the buffer solution used.

Question 1: A sample of DNA shows a higher proportion of guanine than cytosine. What could be the possible implications for the stability of this DNA molecule?

Answer: A higher proportion of guanine may lead to increased stability due to stronger G-C base pairing, which has three hydrogen bonds compared to two in A-T pairs.

Question 1: Explain how the structure of an amino acid determines its role in protein formation, including the significance of the R-group.

Answer: The amino acid's structure includes an amino group, a carboxyl group, and a variable R-group (side chain). The R-group determines the amino acid's properties, such as polarity and reactivity, influencing how it interacts within proteins to determine folding, function, and specificity.

Question 1: Describe how knowledge of amino acid sequences is used in the biotechnology industry, particularly in the development of personalised medicine.

Answer: Amino acid sequences are determined through DNA sequencing, enabling the design of tailored drugs and therapies based on an individual’s genetic makeup, leading to personalised medicine approaches.