Chapter 3- From Genes to Proteins Flashcards
what was Griffith’s experiment?
worked with two forms Pneumococcus, one was an encapsulated bacterium that forms smooth colonies and causes death when injected into mice, the other is a mutant strain that lacks the enzymes needed to synthesize a capsule and forms rough colonies and does not cause death when injected into mice; found that when he heat-treated wild-type did not cause death in mice because it destroyed the capsule; found that when he combined heat-treated wild type and mutant type, the mouse died and he found encapsulated bacteria in the mouse tissue, indicated that the mutant strain had incorporated the virulent element from the heat-treated wild type; concept of “transformation”
what was the Avery , Macleod, and Mccarty experiment?
determined that DNA was the transforming principle, found that transformation still occurred if other bio molecules were destroyed by enzymes, but that transformation would not occur if the sample was given enzymes that destroyed DNA
what was the Hershey and Chase experiment?
When bacteriophages containing 32P (radioactive), were allowed to infect nonradioactive bacteria, all the infected cells became radioactive and, in fact, much of the radioactivity was passed on to the next generation of bacteriophages.
However, when the bacteria were infected with bacteriophages labeled with 35S, and then the virus coats removed (by whirling them in an electric blender), practically no radioactivity could be detected in the infected cells.
because P is in DNA and S is in proteins, indicated that DNA was the molecule of heredity
what was the model developed by Pauling and Corey?
DNA adopts a triple-helical structure, three chains tightly packed together, phosphate on the inside of the triple helix, nitrogenous bases on the outside, stabalized by hydrogen bonds between the interior phosphate groups
which bases are purines?
adenine and guanine
which bases are pyrimidines?
cytosine, thymine, and uracil
which bases does DNA contain?
A,C,T, and G
which bases does RNA contain
A,C,U and G
what forms a nucleoside?
linking atom N9 in a purine or atom N1 in a pyrimadine to a five-carbon sugar at C 1’
what is the sugar in DNA
2’-deoxyribose (2’ C contains a H attached to it instead of an OH
what is the sugar in RNA
ribose
what is a nucloeotide?
nucleoside to which one or more phosphate groups are linked, typically at C5’ of the sugar
what are the functions of nucleotides?
building blocks for DNA and RNA, involved in energy transduction, intracellular signaling, and regulation of enzyme activity
what is the linkage between nucleotides?
phosphodiester bond (single phosphate group forms ester bonds to both C5’ and C3’)
what happens when a nucleoside triphosphate is added to the polynucleotide chain?
a diphosphate group is eliminated
what is a residue?
what a nucleotide is formally known as once incorporated into a polynucleotide
what does the nucleic acid structure look like?
nucleotides consecutively linked by phosphodiester bonds in which the bases project out from a backbone of repeating sugar-phosphate groups
what is the 5’ end?
the end of the polymer that bears a phosphate group attached to a C5’
what is a 3’ end?
the end of the polymer that bears a free OH group
how are base sequences in a polynucleotide read?
from 5’ end to 3’ end
how are the two strands of DNA connected
hydrogen bonds between base pairs
what are Chargaff’s rules?
A=T, C=G; A+C=G=T
how many hydrogen bonds like adenine and thymine?
two
how many hydrogen bonds link guanine and cytosine?
three
why is the sugar-phosphate backbone of the two strands of DNA separated by a constant distance?
all base pairs, consist of a purine and pyrimidine, have same molecular dimensions ( about 11 A wide)
what is the shape of DNA?
double helix, the two strands twist around each other
