intro to dna - (lecture 8) Flashcards
who discovered dna in 1869?
miescher
what did miescher do?
- investigated the chemical composition of the nucleus
- isolated on organic acid that was high in phosphorus and nitrogen
- called it nuclein
what does dna mean?
deoxyribonucleic acid
before thorough research, the general belief was that ______ were the genetic material
proteins
scientists at the time who believed that proteins were the genetic material’s line of thinking was…
- heritable traits are diverse
- molecules containing traits must be diverse
- proteins are made of an “infinite” assortment of 20 amino acids and are structurally diverse
the four nucleotides are…
adenine, thymine, cytosine, and guanine
the two purines are…
adenine and guanine
the two pyrimidines are… (they both have y’s)
thymine and cytosine
who discovered transformation in 1928?
griffith
what did griffith do?
- attempted to develop a vaccine for pnemonia
- isolated two strands of Streptoccocus pneumoniae
- rough strand: harmless
- smooth strand: pathogenic
what happened when griffith injected a mouse with a rough strand? with a smooth strand?
rough strand: the mouse lived
smooth strand: the mouse died
what happened when griffith injected a mouse with heat treated smooth strand cells?
the mouse lived, since all bacteria were dead
what happened when griffith injected the mouse with dead rough strands with smooth strand?
the mouse died, since the harmless rough cells had been transformed by material from dead smooth cells
- descendants of the transformed cells were also pathogenic
who defined the “transforming material” within these prokaryotic cells?
avery and mccarty
what did avery and mccarty do?
- they found that cell extracts treated with protein digesting enzymes could still transform bacteria
- the cell extracts that were treated with dna digesting enzymes lost their transforming ability
what is the bottom line of avery and mccarty’s experiments?
dna is the transforming material; when it is destroyed then they can no longer transform
avery and mccarty went one step further, defining that…
proteins weren’t necessary at all:
- injections without the protein vs. ones without the dna = dna is the transformative material
what is the name of a virus that infects solely bacteria; dna with a protein coat?
bacteriophage
describe what a virus is
nonliving structures with protein coats protecting genetic material (either dna or rna; usually rna)
who took avery and mccarty’s work and used it on bacteriophages?
hershey and chase
what did hershey and chase do?
created labelled bacteriophages
- radioactive sulfur (in protein but not dna)
- radioactive phosphorus (in dna but not protein)
then allowed labelled viruses to infect bacteria, looked for where the radioactive labels were after infection
where was the radioactive sulfur? where was the radioactive phosphorus?
the sulfur was around the bacteriophage’s shell, the phosphorus was inside of the infected cell
all nucleotide bases have…
a nitrogenous base, a 5-carbon sugar, and a phosphate group or groups
acids _____ hydrogens and _____ the pH
donate, lower
