Questions and Answers
What technique did Rosalind Franklin and Maurice Wilkins use to analyze the structure of DNA?
X-ray crystallography
According to Chargaff's rules, what is the relationship between the number of T's and A's in a DNA molecule?
They are always equal
What distance in the X-ray scattering pattern suggested the width of the DNA helix?
2.0 nm
For DNA molecules to have a regular and repeating structure, what conclusion did researchers draw from the X-ray scattering patterns?
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Which pair of scientists, along with Wilkins, were awarded the Nobel Prize in Physiology or Medicine in 1962 for their work on the structure of DNA?
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What did Watson and Crick propose as the arrangement of two strands of DNA in their model?
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What is one of the fundamental characteristics shared by organisms as mentioned in the text?
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Who coined the term 'cells' for the structures observed in cork tissue?
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Which scientist famously stated that the 'dream of a bacterium is to become two bacteria'?
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What role does genetic information play in organisms?
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Which process do organisms engage in to maintain stable internal conditions?
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What is one way organisms acquire energy as mentioned in the text?
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What did Sidney Altman and Thomas Cech receive the 1989 Nobel Prize in Chemistry for?
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What is a characteristic of ribozymes?
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What does the discovery of ribozymes suggest about the relationship between RNA and proteins?
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What is the significance of the RNA world hypothesis?
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Which of the following processes were enzymes and possibly ribozymes involved in according to the text?
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What selective advantages led to the evolution of new functions according to the text?
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Study Notes
DNA Structure
- Watson and Crick knew that DNA has a sugar-phosphate backbone
- Erwin Chargaff established two empirical rules: (1) equal number of purines and pyrimidines, and (2) equal number of T's and A's, and C's and G's
- Rosalind Franklin and Maurice Wilkins used X-ray crystallography to calculate distances between groups of atoms in DNA, revealing repeating distances of 0.34 nm, 2.0 nm, and 3.4 nm
- The scattering patterns suggested a helical structure with a 2.0 nm-wide width and 0.34 nm distance between bases stacked in a spiral
- Watson and Crick arranged two strands of DNA with sugar-phosphate backbones on the outside and bases on the inside, forming purine-pyrimidine pairs
Characteristics of Life
- An organism is a living entity made up of one or more cells
- Five fundamental characteristics of life:
- Cells: membrane-bound units that regulate passage of materials
- Replication: goal of reproducing oneself
- Evolution: products of evolution, continuing to evolve today
- Information: processing hereditary information encoded in genes
- Energy: acquiring and using energy to stay alive and reproduce
Cells and Evolution
- Robert Hooke coined the term "cells" in 1665, observing small compartments in cork tissue
- Two hypotheses on the origin of cells:
- unknown
- unknown
RNA Structure and Function
- RNA molecules have different shapes and chemical properties based on base sequences
- RNA can function as a catalytic molecule (ribozyme or RNA enzyme)
- Sidney Altman and Thomas Cech discovered catalytic RNAs, winning the 1989 Nobel Prize in chemistry
- Ribozymes catalyze reactions similar to protein enzymes
- Tetrahymena ribozyme catalyzes hydrolysis and condensation of phosphodiester linkages in RNA
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Description
Test your knowledge on the key discoveries in DNA structure by Watson, Crick, Chargaff, Franklin, and Wilkins. Learn about the sugar-phosphate backbone, base pair rules, and X-ray analysis findings.
