2.3 Genetic code and translation Flashcards
What organ plays an important role in defense against infection?
Spleen
What is Haploinsufficiency?
Not getting enough good copy of the gene
What is the One gene, one enzyme hypothesis?
genes function by encoding enzymes, and each gene encodes a separate enzyme
What is the evidence for one gene, one enzyme hypothesis?
Began with Beadle and Tatum in isolating axotrophic mutants in Neurospora. They began working on this fungus(neurospora) and making mutants that wouldnt grow on the media. However, if you gave it amino acids it could grow and thus worked with this about how genes encode for amino acids
what protein makes light in fireflies?
luciferase
What protein is a major structural component of spider webs?
Fibroin
What protein is highly toxic in castor beans?
Ricin
What is a peptide bond?
carboxyl group of one AA is covalently attached to the amino group of another AA.
Sequence of the 21 amino acids, how they are joined together determines what?*
How they interact with each other.
What does the genetic code determine?
How the nucleotide sequence specifies the amino acid sequence of a protein
How was the specificity of codons determined?
Using a homoploymer. They realized that if we could synthesize RNA (all Gs or Cs), then at least we could figure out what these blocks coded for. Got a tube where template is all used with all AA is there, translations happens and they see what got hooked with what. They look at the strand that results from this, this worked out what the 4 homo polymers were. They then synthesized RNA more specifically, in the next 5-6 years they worked out the entire set. They did it via radioactively. Finally they did the entire codon table
What is a codon?
a triplet RNA code
What are the 64 possible codons?
3 stop, 61 sense codons
What are the stop codons?
UAA, UAG and UGA
What is the significance of stop codons?
If an AA gets coded into a stop codon, huge devistation occurs.
What is the initiation codon for the open reading frame?
AUG
What is a degenerate code?
AA may be specified by more than one codon
What are synonymous codons?
Codons that specify the same AA
What are isoaccepting tRNAs?
different tRNAs that accept the same AA but have different anticodons
What are the three codons?
Sense, initiation and termination
What is the intiation codon?
AUG
What are the termination codons?
UAA, UAG and UGA
What is the wobble hypothesis
The 3rd nucleotide of a codon interaction is flexible. Doesnt have to pair perfectly and results in some tRNAs bringing in wrong AA
Why is the wobble hypothesis important?
Importance of variation. Why multiple codons can code for a single amino acid.
What is the reading frame?
Is a way of dividing the sequence of nucleotides into a set of consecutive, non-overlapping triplets. Nearly universal
Amino acids are assembled into a protein through what?
Translation
What are the 4 steps to translation?
- Charging-binding of AAs to tRNAs. 2. Initiation of translation. 3. Elongation of peptide chain. 4. Termination
The specificity between an amino acid and its tRNA is determined by what?
Each individual aminoacyl-tRNA synthesis
How many different aminoacyl-tRNA syntheses are in a cell?
20
At what end does the amino acid attach to of a tRNA?
3’ end
What is the acceptor end?
Where tRNA gets the amino acid (chargin it)
The sequence of the tRNA is how amino acid
specificity is established
What is needed for the initiation of translation?
Initiation factors 1F-3, fmet-tRNA and GTP
What is the Kozak sequence?
in euk cells facilitates the identification of the start codon
What is the shine-dalgarno consensus sequence?
in prok, mRNA is required for the attachment of the small subunit of the ribosome
What does the poly A tail of euk mRNA do in translation?
Plays a role in the initiation of translation
What are the 3 steps to elongation during translation?*
- Charged tRNA binds to A site of ribosome. 2. Formation of peptide bond between P and A site. 3. Ribosome translocates to next codon
When does translation end?
When a stop codon is encountered.
True or False? An mRNA molecule may be transcribe simultaneously by several ribosomes
True. but only in euk.
