Exam 3: Properties and Structure of DNA Flashcards
List the requirements of genetic material
-Stores information
-Expresses information
-Transmits information
-Has the capacity to vary
-Can be translated into a phenotype
-Efficiently and accurately replicated
Describe the central dogma of biology
Information flows from DNA to RNA to protein.
DNA makes RNA through transcription, and RNA makes protein through translation.
Are RNA genomes present in some viruses?
Yes
Describe the nucleotide structure
-nitrogenous base
-pentose sugar
-phosphate group
Compare and contrast DNA and RNA
-Different sugars
DNA: The sugar in the backbone of DNA is deoxyribose, which lacks one oxygen atom compared to ribose.
RNA: The sugar in the backbone of RNA is ribose, a five-carbon sugar with an oxygen atom on the 2’ carbon position.
-Different nitrogenous bases
-ssRNA vs dsDNA
-RNA also in cytoplasm, not just nucleus
Describe the structure of double stranded DNA
Right handed double helix (alpha helix) in antiparallel configuration with complementary sequences
Recognize the contributes of Franklin, Watson, and Crick to the understanding of dsDNA structure.
Rosalind Franklin determined that DNA exists in the helical B form.
Watson and Crick, building upon the work of Rosalind Franklin and others, proposed the double helix model of DNA in 1953. Their model explained how the two DNA strands are complementary and antiparallel, with specific base pairing (A with T and C with G).
Describe and explain Griffith’s Transformation Experiment
Speculated “transforming principle” could be part of polysaccharide capsule or compound required for capsule synthesis… later determined to be DNA.
Live S strain: Mice died from the infection, demonstrating the virulence of the S strain.
Live R strain: Mice remained healthy, as the R strain was non-virulent.
Heat-killed S strain: Mice also remained healthy, indicating that the heat-killed S strain alone was not harmful.
Mixture of heat-killed S strain and live R strain: Mice died. Upon examining the mice’s blood, he found living S strain bacteria. This suggested that something from the heat-killed S strain had transformed the live R strain into virulent S strain bacteria.
Describe and explain the Hershey-Chase Experiment
Used E. coli and bacteriophage T2
They chose to label DNA with radioactive phosphorus-32 (32P) and protein with radioactive sulfur-35 (35S).
In the 32P-labeled DNA experiment, the radioactivity was detected inside the bacterial cells, indicating that the DNA from the T2 bacteriophage had entered the host bacteria.
Demonstrated that DNA, not protein, is the genetic material
Demonstrated DNA enters bacterial cell during infection an directs viral reproduction.
What are the pyrimidines?
Cytosine and thymine
Rosalind Franklin’s X-ray Diffraction
-Crystals of a substance are bombarded with X-rays, which are diffracted (bounce off).
-The spacing of the atoms within the crystal determines the diffraction pattern
-The diffraction pattern provides information about the structure of the molecule
DNA strands run in opposite directions; they are
antiparallel (i.e. 5’ to 3’)
What is the difference between A form and B form DNA?
-B form is predominant; A form exists when little water is present
A ___________ linkage connects the 5’ phosphate group and the 3’ OH group of adjoining nucleotides.
phosphodiester
G-C pairs have ____ hydrogen bonds
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