18 Questions
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?
DNA is helical
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?
Watson and Crick
What did Watson and Crick propose as the arrangement of two strands of DNA in their model?
Sugar– phosphate backbones on the outside and bases on the inside
What is one of the fundamental characteristics shared by organisms as mentioned in the text?
Acquisition and use of energy
Who coined the term 'cells' for the structures observed in cork tissue?
Robert Hooke
Which scientist famously stated that the 'dream of a bacterium is to become two bacteria'?
Francois Jacob
What role does genetic information play in organisms?
Encodes hereditary information
Which process do organisms engage in to maintain stable internal conditions?
Response to environmental information
What is one way organisms acquire energy as mentioned in the text?
Ingesting food
What did Sidney Altman and Thomas Cech receive the 1989 Nobel Prize in Chemistry for?
Showing that organisms have catalytic RNAs
What is a characteristic of ribozymes?
They catalyze reactions similar to protein enzymes
What does the discovery of ribozymes suggest about the relationship between RNA and proteins?
The RNA world preceded proteins in chemical evolution
What is the significance of the RNA world hypothesis?
It implies that RNA predates proteins in evolution
Which of the following processes were enzymes and possibly ribozymes involved in according to the text?
Replicating hereditary nucleic acids
What selective advantages led to the evolution of new functions according to the text?
Random changes in nucleic acids
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
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.
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