Chapter 7: DNA Structure and Replication

Questions and Answers

What did Frederick Griffith identify as the two strains of Pneumococcus?

S and R strains (correct)

Rough and soft strains

Smooth and rough strains

Virulent and avirulent strains

In Griffith's transformation experiment, what could a single gene mutation change do?

Enhance the antibiotic resistance of the strain

Convert an avirulent strain to a virulent strain (correct)

Alter the color of the bacterial colonies

Convert a virulent strain to an avirulent strain

According to geneticists in the 1940s, what was favored as genetic material?

Carbohydrates

Proteins (correct)

Nucleic acids

Lipids

What did Hershey and Chase demonstrate in their experiment using Escherichia coli and bacteriophage T2?

DNA enters bacterial cell during infection and directs viral reproduction Signup and view all the answers

What type of sugar is present in DNA but not in RNA?

Deoxyribose sugar Signup and view all the answers

What did Rosalind Franklin's X-ray diffraction studies reveal about DNA structure?

DNA has a 3.4-angstrom periodicity, characteristic of a helical structure Signup and view all the answers

Which scientist's base composition analysis provided crucial data to Watson and Crick for their DNA model?

Chargaff Signup and view all the answers

According to Watson and Crick's model, how are the two DNA strands connected?

By hydrogen bonding Signup and view all the answers

What did Watson and Crick propose about the structure of DNA?

Double helix with anti-parallel strands Signup and view all the answers

What was the Nobel Prize awarded to James Watson and Francis Crick for in 1962?

Discovery of the DNA double helix structure Signup and view all the answers

What are the four key characteristics that the genetic material must exhibit?

Replication, storage of information, expression of information, and variation by mutation Signup and view all the answers

Which two scientists independently described the parallels between chromosome partitioning into gametes and the inheritance of genes?

Walter Sutton and Theodor Boveri Signup and view all the answers

What was the evidence that made DNA a candidate for the hereditary material?

DNA was localized to chromosomes Signup and view all the answers

In what year were Mendel's hereditary principles rediscovered?

1900 Signup and view all the answers

How many hydrogen bonds are formed between a guanine (G) and cytosine (C) base pair?

3 Signup and view all the answers

Which of the following statements about the DNA structure is correct?

The two strands of the DNA helix run in opposite directions (antiparallel). Signup and view all the answers

Which of the following experiments provided evidence for the structure of DNA?

All of the above Signup and view all the answers

What is the significance of Chargaff's rules of base composition in the discovery of the DNA structure?

It revealed the complementary base pairing between A-T and G-C. Signup and view all the answers

Who were awarded the Nobel Prize in 1962 for their contribution to the discovery of the DNA structure?

James Watson and Francis Crick Signup and view all the answers

Study Notes

Griffith's Transformation Experiment

Frederick Griffith identified two strains of Pneumococcus: S (smooth) and R (rough)
S strain is virulent and causes fatal pneumonia in mice, while R strain is avirulent
A single gene mutation can convert an S strain to an R strain

The Avery, MacLeod, and McCarty Experiment

Experiment in 1944 showed that DNA is the hereditary molecule
Provided foundation for understanding the transforming principle

Hershey-Chase Experiment

Experiment in 1952 used Escherichia coli and bacteriophage T2
Used radioisotopes 32P and 35S to demonstrate DNA enters bacterial cell during infection and directs viral reproduction
Demonstrated that DNA, not protein, is the genetic material

Structure of DNA

Nucleotides consist of a nitrogenous base, pentose sugar, and phosphate group
Nucleosides contain nitrogenous base and pentose sugar
Nucleotides are linked by phosphodiester bonds between phosphate group at C-5' position and OH group on C-3' position

Erwin Chargaff's Rules of Base Composition

The amount of T = A, the amount of C = G
The amount of pyrimidine nucleotides (T+C) = purine nucleotides (A+G)

Rosalind Franklin's X-ray Diffraction Analysis

X-ray diffraction analysis of DNA showed a 3.4-angstrom periodicity, characteristic of a helical structure
Data provided crucial information for Watson and Crick's model of DNA

Watson and Crick's Double Helix Model

Proposed structure of DNA as a double helix with two anti-parallel strands connected by base pairing
Stacked nitrogenous bases and sugar-phosphate backbone form the structure of DNA

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Description

This quiz covers topics related to DNA structure, replication, nucleic acid chemistry, evidence supporting DNA as the genetic material, RNA structure, and criteria for genetic material. It also includes information about Mendel's rediscovery.