Lecture 7 Flashcards
Two of the most important biological investigations of the twentieth century were to
1) find what is the genetic material of life
2) elucidate the structure of that material
the genetic material of organisms was unknown. Possible candidates included
polysaccharides, DNA, lipids, proteins, etc.
many thought that ___ were the most likely candidate for the genetic material of organisms given ___
proteins
DNA –> simple repetitive molecule
proteins –> thousands of various forms.
In a series of famous experiments by ____ the case was settled, DNA was the hereditary molecule
1) Avery, MacLeod, and McCarty (1940’s)
2) Hershey and Chase (1951/1952)
the famous experiments that showed DNA was the hereditary molecule
infect mouse with virulent S strain bacteria (combined with a living non-virulent R strain)
only when the DNA of the virulent strain is destroyed that the mouse lives
One key to that lead to the discovery of the structure of DNA came from ____
who ___
Rosalind Franklin
- stretched vicious fluids containing DNA
- and projected x-rays through the strands
- and used photographic plates to gather the refracted x-rays.
Depending on the preparation method (e.g. pH, and water content) she found differing patterns (for DNA structure, A-DNA and B-DNA)
She was methodical in her approach beginning work on the ___
A-form (A-DNA)
but the B-DNA form represented the typical biological shape of DNA. this form was worked on by J Watson and F Crick
Professor Franklin was a ___
Her primary school was unusual because __
she worked in the ___ field
she died in ___ at the age of _____
intellectual power recognized even in childhood
it prepared girls for careers rather than being a typical house wife
in many fields
1958 at the age of 38.
June (Broomhead) Lindsey was a ___
awarded her first degree in 1944 (doctorate in 1950), and then joined the ___ where she ___
gifted researcher
Cavendish lab at Cambridge
discovered base shapes and H bonding in DNA
____ proposed that “nucleobases” are bound to each other via hydrogen bonds
June (Broomhead) Lindsey
____ directly used ____ work to clarify the structure of DNA. However, they did not cite her papers or give her any credit.
Watson and Crick (“discovered” the structure of DNA in 1953)
Lindsey’s
DNA structure is a ___
with ___ as backbone
double helix with
phosphates & pentose sugars –> backbone
and nucleotides in the middle.
Sugar in DNA ___
Phosphates in DNA ___
lacks a typical oxygen and thus “de-oxy” ribose nucleic acid;
have a negative charge making DNA slightly acidic (thus a nucleic “acid”).
The nucleotides have a specific complimentary pairing of
one purine (two ringed molecule) with one pyrimidine (one ring), A to T and G to C.
Purine vs Pyrimidine
Purine - A & G
Pryimidine - T & C
(AT, GC)
ratio of AT/CG
is variable & differs significantly by the taxonomic group (organism AND part of DNA loking at –> AT/CG rich regions)
____facilitates the macro structure of DNA.
The specific complimentary bonding of the nucleotides
____ makes the DNA much more stable and thus less likely to degrade.
very tight spacing of the molecule, excludes H2O
stacked in middle –> single/double allows adjacent (above and below) close stacking –> excludes H2O
the shape of the molecule produces a ”major” grove that is larger, and a smaller “minor” grove.
these spaces are important ___
for proper protein (structural and regulatory) binding to the helix.
chromatin
DNA + proteins (e.g. histones)
actual/typical structure of DNA
tends to be condensed via wrapping around proteins (e.g. histones) into chromatin. “middle ground” - not completely uncondensed or fully condensed in cell devision
The basic histone spool is a
octamer of 8 subunits (2 copies of 4 proteins)
____ facilitate DNA spooling.
are additional histones (e.g. H1)
The regulation of chromatin (histone) binding is one key factor in
the regulation of DNA replication and transcription.
