Translation Flashcards
What cellular components are involved in translation?
-Initiation, elongation and release factor proteins
-tRNA
-Synthetase enzymes
-rRNA
-Ribosomal proteins
What is the function of synthetase enzymes
Facilitating the correct matching of tRNA and amino acids
what is the function of tRNA?
Transfers amino acids from a pool of cystoplasmically situated amino acids to a growing polypeptide strand
Each ____ is not ______ and can translate a specific mRNA _______ into a specific amino acid
tRNA, not identical, codon
How many nucleotiddes are in a tRNA molecule?
70-90
What are the different regions of the tRNA molecule?
-DHU loop
-Anticodon loop
-Amino acid attachment site
In a tRNA molecule there are __ double helical segments and __ loops
4, 3
What is an anticode region?
A specific nucleotide triplet taht forms complimentary base pairs with an mRNA codon for an amino acid
Written 3’-5’ and align with the codon 5’-3’
What is located at the 3’ end of tRNA and what is it for
-The CCA sequence
-Terminal adenine is the point of attachment during tRNA activation with an amino acid
Which enzyme allows tRNA activation? Describe how it works
-aminoacyl tRNA synthetases
-Specific to the type of tRNA and amino acid (there are 20)
-Active site of the enzyme recognizes the anticodon end
-Enzyme catalyzes the covalent attachment of the molecules from ATP hydrolysis
How many tRNA molecule variations are there
45, some can bind to more than 1 codon due to wobble hypothesis
There are 64 codons and 20 amino acids
What is the wobble hypothesis?
tRNAs always pair their anticodons with the first 2 bases of thee codon, but the third is more flexible
How is translation initiated in eukaryotes?
-Translation initiation complex forms
-Forms towards 5’ cap
-mRNA is scanned until AUG is found
How is translation initiated in prokaryotes?
-Forms at 1 or more ribosome binding sites called shine-dalgarno sequences located a few nucleotides upstream of AUG
Define polycistrionic
2 or more separate proteins are encoded in 1 mRNA molecule; mRNA contains multiple genes controlled by a single promoter and terminator
(prokaryotic feature)
What factors does translation initiation include?
-Large and small ribosomal subunits
-mRNA
-charged tRNA methionine
-Initiation factors (help assemble complex)
How does the initiation complex assemble
-Initiation factors ind to 5’ cap
-Small ribosomal subunit joins
-Other initiation factors bind to methionine tRNA
-Partial compllex finds AUG on mRNA
-Large subunit binds using GTP hydrolysis
Polypeptides are synthesized from the ___ end to the ____ end
amino end to the carboxyl end
Where will methionine be located at the beginning of elongation
the peptidyl site
Where do tRNAs enter and bind in the ribosome
The aminoacyl site
What is a GTP elongation factor
-Delivered with each charged tRNA
-When codon pair is made, GTP is hydrolyzed and aminoacyl end of tRNA is released from the elongation factor
Which site does the deacylated tRNA move to
The exit site
What happens when the stop codon is reached on the mRNA
-GTP-bound release factors bind to the A-site
-Bond is broken between the terminal amino acid and the P-site tRNA
-GTP hydrolysis enables dissociation of the translation complex
Which hypothesis was developed using Neurospora Crassa?
one-gene-one-enzyme hypothesis
Can bread mold grow on a medium lacking arginine?
Yes, it can make its own from a series of steps requiring specific enzymes
Precursor–>ornithine–>citruline–>arginine
