Theme 2A Flashcards
How does information flow to convert genotype into phenotype in the Central Dogma?
DNA to RNA to protein. This information flow is universal and common to all forms of life.
(some viruses can perform reverse transcription)
Where does transcription and translation occur in prokaryotes?
They occur simultaneously in cytoplasm
Where does transcription and translation occur in eukaryotes?
Transcription and the processing of precursor mRNA molecules occur in the nucleus, translation occurs in the cytoplasm
What is the one gene one enzyme (protein) hypothesis?
Beadle and Tatum hypothesized that genes encode enzymes that function at each step of a biosynthesis pathway to make an essential nutrient (specifically investigated studied the mould Neurospora)
What would happen if you mutated a gene encoding an enzyme in a biosynthesis pathway?
It would block the metabolic pathway and the organism can no longer synthesize the needed nutrient
What is an auxotroph?
Organism that cannot make its own essential nutrients
Describe the steps in the experiment that led to one gene one enzyme hypothesis?
Arginine Auxotrophic Mutants
- Mutants of Neurospora (failed to grow in the absence of arginine) were isolated
- Each mutant had a defective gene for an enzyme needed to synthesize a product to produce arginine
What does it mean when something can grow on minimal media?
No extra supplements are needed
Where does information flow occur?
Genes on chromosomes
What types of RNA do genes encode for?
- Coding RNA (mRNA): codes for proteins/polypeptides
- Non-coding RNA (tRNA, rRNA): does not code for a protein
What are the three letter codes for DNA and RNA?
- DNA: triplets
- RNA: codons
Genetic code is universal, same code in prokaryotes, eukaryotes, and viruses.
Describe the template strand in DNA.
- Read in the 3’-5’ by RNA polymerase
- For every gene, one RNA molecule is produced from one of the DNA strands
Describe the non-template strand.
- Also known as the sense/coding strand
- This strand looks the same as the mRNA molecule (except with uracil instead of thymine); mRNA transcript is read in the 3’-5’ by RNA polymerase
What directions to transcription and translation occur?
Transcription occurs in the 5’-3’. For translation (protein synthesis), the mRNA codons are read in the 5’-3’
How are genes represented on chromosomal maps?
They are shown as arrows on the sense strands
How do viruses accomplish reverse transcription?
In some viruses with RNA genomes there is an enzyme called reverse transcriptase. Viral RNA needs to be converted into viral DNA in order to get into the hosts chromosomes. So the hosts transcription and translation is hijacked to produce viral proteins from viral DNA
