DNA Structure and Replication Quiz

DNA Structure and Replication

• Chromosomal Theory of Inheritance: Chromosomes carry hereditary information. This was confirmed in 1910 by Thomas Morgan Hunt, who observed sex-linked traits in fruit flies.
• Griffith's Experiments (1920s): An unknown substance (transforming principle) from virulent bacteria could transform non-virulent bacteria into virulent ones. This hinted at a hereditary chemical.
• Avery's Experiments (1940s): Determined the transforming principle was DNA. He used enzymes to break down components of bacteria (DNA, RNA, protein), and found only degrading DNA prevented transformation.
• Hershey-Chase Experiment (1950s): Proved DNA, not protein, is the hereditary material in viruses. They labeled phage DNA and protein with different radioactive isotopes and tracked which entered bacterial cells.
• DNA Structure: DNA is a polymer of nucleotides with a sugar-phosphate backbone and four nitrogenous bases (A, G, T, C). Purines (A, G) have a double ring structure, and pyrimidines (T, C) have a single ring structure. Complementary base pairing occurs (A with T, G with C).
• Chargaff's Rules: The amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine. This demonstrated a predictable ratio and was key to understanding complementary base pairing.
• Watson and Crick (1953): Determined the double helix structure of DNA using X-ray diffraction data from Rosalind Franklin.
• DNA Replication: DNA replication is semi-conservative, meaning each new DNA molecule has one original strand and one new strand.
• Meselson-Stahl Experiment (1958): Demonstrated DNA replication is semi-conservative. They used radioactive isotopes (15N and 14N) to tag parental and new DNA strands. Centrifugation separated the differing weights of the molecules showing the new DNA molecules consisted of half new DNA molecules and half original DNA molecules.

Test your knowledge on DNA structure, replication, and key experiments that shaped our understanding of genetics. This quiz covers concepts like the Chromosomal Theory of Inheritance and significant experiments by Griffith, Avery, and Hershey-Chase. Dive into the molecular basis of heredity and challenge yourself!