Questions and Answers
Which of the following are characteristics that a molecule must exhibit to serve as genetic material? (Select all that apply)
Proteins were initially favored over nucleic acids for their diversity.
True
What was proved by Avery et al. in 1944?
DNA is the transforming principle responsible for heredity.
The central dogma of molecular genetics states that DNA makes _____, which makes proteins.
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What did Griffith’s experiment with Streptococcus pneumoniae demonstrate?
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What molecule was identified as the transforming principle in Avery's experiment?
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What was the focus of the Hershey-Chase Experiment?
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Study Notes
Properties of Genetic Material
- Genetic material must exhibit replication, meaning it can be copied during mitosis and meiosis.
- It must store information, encoding gene products and transmitting diverse information to progeny cells.
- The material needs to express stored information, following the central dogma where DNA converts to RNA, which then encodes proteins.
- Genetic variation is essential; mutations can be inherited and distributed within populations.
Initial Preference for Proteins
- Proteins were regarded as better candidates for genetic material because of their diversity and abundance.
- Extensive prior knowledge existed regarding proteins compared to the understanding of nucleic acid chemistry.
- Levene's tetranucleotide hypothesis incorrectly suggested equal ratios of DNA bases A, C, G, and T, disproven by Erwin Chargaff's findings.
Evidence Supporting DNA as Genetic Material
- 1944: Avery et al. published findings that identified DNA as the "transforming principle," crucial for heredity in bacteria.
- 1927: Griffith's experiment laid the groundwork for Avery, demonstrating virulence in Streptococcus pneumoniae through strain experimentation.
- Griffith used IIR (non-virulent) and IIIS (virulent) strains; injected both into a mouse expecting survival but led to the mouse's death.
- He discovered live S-strain bacteria in the dead mouse, concluding that the R-strain had been transformed by the S-strain, coining it the "Transforming principle."
Avery et al. Experiment (1944)
- Avery identified DNA as the agent that transformed non-virulent strains to virulent ones, confirming its role in heredity.
- Conducted experiments isolating various cellular components from virulent strains—only DNA achieved transformation.
Hershey-Chase Experiment (1952)
- Focused on Escherichia coli and its bacteriophage T2, illustrating that DNA carries genetic information.
- The experiment involved the structure of phages: a DNA core enveloped by a protein coat.
- Upon phage infection, only DNA penetrated the bacterial cell, leaving the protein coat outside, affirming DNA as the genetic material.
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Description
Explore the essential properties of genetic material in this quiz based on Chapter 10 of Genetics 244. Understand the context and details needed for success in the module. Prepare effectively for the upcoming assessments.
