Chapter `16 Flashcards
What question did Beadle and Tatum test with Arginine metabolic pathway?
If there was a 1:1 ratio of genes to proteins.
What is a genetic screen?
- Who used this to test what?
pt. 1
1- you take a large population of cells. ( Nauraspa cells)
2- randomly mutagenize the genes in those cells.
( via UV or X-ray), so each cell has a random group of mutations then.
3- Place on media and allow for growth (containing Arginine)
4- transfer cells to media that lacked arginine.
5- Screen through the population looking for phenotypes that are indicative of a problem in whatever process you are studying. (look for cells that only grew in the presence of arginine.)
5- then you take the ones you interested in and study them further, to see where the mutations are.
6- establish a relationship between mutants and enzymes.
7- take each mutant( grew only the presence of arginine) and grew it in either ornithine or in citrulline or in arginine and used that data to characterize what step in the pathway that mutant was defective in.
( ornithine, citrulline or in arginine* are all steps in the metabolic pathway to get to arginine.)
What were the results of beadle and Tatum’s genetic screen?
- They found three different types of mutants each associated with a defect in enzyme one, two, or three. Which further suggest that…
- The one-gene, one-enzyme hypothesis is correct.
precursor—>ornithine—>citrulline—>arginine
Given this metabolic pathway, and if the mutant cells produced as a result of a genetic screen only saw growth in citrulline and arginine the cells would lack which enzymes
enzyme two.
t/f every gene encodes for only one protein?
false, Beadle and Tatum’s experiment pointed to this idea, but that is not totally true.
- most of the time genes will encode just for one protein, but sometimes genes can encode for more than one protein.
What is the genetic code?
- How the sequence of nucleotides in a gene is ultimately converted to the sequence of amino acids in a protein.
What is the function of ribosomes and where are they found?
Where is DNA found?
- protein synthesis, in the cytosol and rough ER
- Nucleus.
Since DNA is in the nucleus and ribosomes that synthesis proteins are in the cytosol, how do you carry the genetic information from the nucleus out to the ribosomes?
mRNA
What is mRNA?
- The genetic information in the DNA is used to make a different type of nucleotide called an mRNA, which is then exported to the cytoplasm, where they are read by ribosomes ultimately to make the proteins.
What is the central dogma of biology?
- ) Genes are composed of DNA and their role is long term storage.
- ) transcription
- ) mRNA is produced
- ) carries genetic info to the ribosomes.
- ) translation occurs.
What is transcription?
What is translation?
- DNA to mRNA
- Ribosomes reading mRNA and make the corresponding proteins.
What about the central dogma of biology is grossly simplified?
- lack of awareness for differing types of RNA’s:
rRNA & tRNA are necessary for translation
miRNA’s, siRNAs, piwiRNAs (regulate translation)
incRNA’s regulate chromosome structure. - Overall lack of RNA’s associated with translation and transcription.
How are the bases in DNA read?
- the genetic code is read in groups of three base pairs.
- every 3 bases in an RNA is read by the cell to make one amino acid in the corresponding protein.
How do we know what three bases equate to an amino acid?
- begin by making synthetic mRNA of a known sequence.
- put in a test tube with known sequences of amino acids, ribosomes, and tRNA’s ,ect.
- look at the produced peptide and see what the base code produced is.
What is a codon?
- it is a sequence of 3 bases in an mRNA that contain the information needed to make a particular amino acid.
