Question 1: Define the term 'nucleotide'.

Answer: A nucleotide is the basic building block of DNA, consisting of a sugar, a phosphate group, and a nitrogenous base.

Question 2: What are the four types of nitrogenous bases found in DNA?

Answer: Adenine, Thymine, Cytosine, and Guanine.

Question 1: Explain why DNA is described as a double helix.

Answer: Because it consists of two strands twisted around each other in a spiral shape, resembling a twisted ladder.

Question 2: Describe the complementary base pairing in DNA.

Answer: Adenine pairs with Thymine via two hydrogen bonds, and Cytosine pairs with Guanine via three hydrogen bonds.

Question 1: Calculate the number of hydrogen bonds in a DNA molecule with 100 base pairs.

Answer: 200 hydrogen bonds (since each base pair has 2 hydrogen bonds).

Question 2: If a DNA strand has 500 nucleotides, how many phosphate groups does it contain?

Answer: 500 phosphate groups (one per nucleotide).

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

Answer: You can mash the fruit and mix it with a solution of detergent and salt to break down cell membranes and release DNA. Filter the mixture and add alcohol to precipitate the DNA. Safety precautions include wearing gloves and eye protection, and handling chemicals in a well-ventilated area.

Question 1: A scientist finds that a DNA sample has a high proportion of Cytosine and Guanine bases. What might this indicate about the stability of the DNA?

Answer: A high GC content suggests the DNA is more stable due to the three hydrogen bonds between Cytosine and Guanine, making it more resistant to denaturation.

Question 2: Explain how understanding DNA structure is crucial in the development of genetic engineering technologies.

Answer: Knowledge of DNA structure allows scientists to manipulate genes precisely, insert or delete specific sequences, and develop techniques like CRISPR. This understanding enables improvements in medicine, agriculture, and biotechnology.

Question 1: How is DNA sequencing used in forensic science?

Answer: DNA sequencing allows forensic scientists to identify individuals based on their unique DNA patterns, helping solve crimes.

Question 2: Describe a potential ethical concern related to manipulating DNA in humans.

Answer: Manipulating human DNA raises ethical issues such as consent, potential unintended consequences, and the possibility of creating 'designer babies' with selected traits, which could lead to social inequality.