Molecular Basis of Inheritance Flashcards
how did griffith’s DNA/protein mice experiment indicate that genetic material was made of DNA, not proteins?
-a mouse is given live “S cells” and dies
-a mouse is given “R cells” and survives fine
-a mouse is given heat-killed “S cells” and is fine
-then, a mouse is given R cells and a mixture of heat killed S cells, and dies
-therefore, the R cells must have been transformed into the S cells by an “unknown, heritable substance”
what were avery and schrodinger’s contributions to DNA research?
avery - the R cell -> S cell transformation can only occur if the DNA is intact
schrodinger - argued that genes are made of individual subunits
what are DNA molecules made of?
-pyrimidines (C and T)
-purines (A and G)
purines are wider than pyrimidines
what is chargaff’s rule?
-although base composition varies in species, the # of A:T bases are equal, and the number of C:G bases are equal
what was the hershey/chase experiment for determining if protein or DNA allowed bacteria to reproduce?
-bacteriophages were injected with substances that could visualize proteins and DNA separately
-the protein coloured bacteria were only visible on the outside of the cell, meaning no protein had been injected into the bacteria cell (found in supernatant once centrifuged)
-the DNA colouring was found inside a centrifuged “pellet,” meaning it was in the bacterial cell itself
what is DNA structurally composed of?
-a hydrophobic nitrogenous base [ATCG]
-a deoxyribose sugar with 5 carbons
-a negatively charged phosphate group
-held together by weak hydrogen bonds
what does DNA actually do?
-codes for protein synthesis and acts as a template for RNA synthesis
what is semi-conservative DNA replication?
-the hypothesis that when DNA replicates, each new double helix strand is composed of one original “old” strand and one replicated “new” strand
what were the conservative and dispersive models of DNA replication?
conservative: one entirely new double helix would be created and the original double helix would stay as it is
dispersive: the original DNA strands would “disperse” and be equally spread out for both replicative strands
how did meselson and stahl conclude the semi conservative replication of DNA was correct?
-bacteria were grown in a heavy isotope of nitrogen and then transferred to a lighter isotope of nitrogen
-DNA was centrifuged after the 1st and 2nd replication, showing that there were 2 “bands” of replication: the 1st band being from the heavier isotope, and the 2nd band being the lighter isotope
where does DNA replication begin?
-at the origin of replication
-eukaryotes have hundreds of origins, bacteria only have one
how does replicated DNA elongate?
-by following a replication fork (place where DNA unwinds)
-DNA is read from 5’ to 3’ , and the complimentary strand is created in the 5’ to 3’ direction as well, never 3’ to 5’
what does the helicase enzyme do?
-unwinds the DNA double helix to begin replication
what do single stranded binding proteins do?
-bind to the separated strands of DNA to prevent them from snapping back together
what does the primase enzyme do?
-creates an RNA primer on a separated strand of DNA to serve as an “initiation point” for DNA polymerase
