Genes and Genomic Organization Flashcards
What early evidence showed that genetic material could be transferred between organisms?
Frederick Griffith conducted experiments with rough and smooth strep bacteria.
Injecting mice with the s form killed them.
Injecting mice with spontaneously transformed r form (that was originally s form) allowed the mice to live.
Injecting heated s-form into the mice left them alive along with cellular debris, indicating there must be a live strain to be virulent.
When cellular debris and the r-form were injected, the mouse died. Cultured bacteria taken from the mouse contained the S-form, even though it was not alive.
This indicated that despite cell death, information was encoded that allowed the r-form to take on s-form’s shape and virulence; indicating the presence of transferable genetic information.
What early evidence showed that DNA was genetic material being transferred between organisms?
Frederick Griffith performed experiments where he mixed live r-form and heat killed s-form together to see under which conditions the r-form would transform.
1. When protease was added to destroy protein, the r-form still transformed.
2. When RNAse was added to destroy RNA, the r-form still transformed.
3. When the tube underwent ultracentrifugation to eliminate fat, the r-form still transformed.
4. When DNAse was added to destroy DNA, no transformation occurred.
Explain the experimental results that led to the “one gene, one enzyme” hypothesis.
Beadle and Tatum introduced random mutations into the yeast genome with an X-ray and screened for mutants with particular problems. Wild type yeast cells efficiently make any amino acids their environments lack themselves; any yeast cells that can’t means the gene needed to make that protein was mutated.
They isolated haploids from the cross, then tested on minimal mediums to force yeast to synthesize amino acids themselves. Different amino acids were added back one at a time to see if they would be rescued.
Performed the same experiments with yeast that could not produce arginine; to figure out where in the pathway the genes acted, the rescue experiment was performed with precursors to arginine. This suggested the idea that each gene corresponds to a particular final enzyme product.
What modern genetic and genomic data suggest the original “one gene, one enzyme” hypothesis was framed too narrowly?
One gene can result in multiple variants. 2 close/adjacent genes can both impact the same enzyme.
What is transformation?
changing the genetic makeup of one organism to that of another
How did the r-form transform into the s-form during Griffith’s experiments?
R cells took up bits of DNA and propagated with a plasmid, leaving the new DNA separate from the genome or incorporating it inside.
What is RNAse?
an enzyme that digests RNA strands; used during the Griffith experiments to prove that RNA isn’t the inheritable genetic material
What is DNase?
an enzyme that digests DNA strands; used during the Griffith experiments to prove that DNA is the inheritable genetic material
What is mutagenesis?
the process by which an organism’s DNA changes, resulting in a genetic mutation
What does haploid mean?
one set of chromosomes
What does diploid mean?
two sets of chromosomes
What is a nonsense mutation?
a stop signal is introduced, leading to premature termination of translation
What is a missense mutation?
a different amino acid is produced than originally expected
What does collinearity mean?
Genes and proteins are collinear. by perturbing DnA and seeing what happens, it can be inferred what the associated genes do
Describe how the TrpA protein in E.coli is collinear.
Mutations of the C terminal of the protein are located on the 3’ end of the nucleotide.
Mutations of the N terminal of the protein are located on the 5’ end of the nucleotide.
How were the fundamental properties of the genetic code discovered?
Crick and Brenner wanted to see if functional proteins resulted from insertions and deletions.
