T2M3 Flashcards
In prokaryotes assembly and translation occurs in the
cytoplasm
Eukaryotic transcription occurs in
nucleus
Eukaryotic translation occurs in the
cytoplasm
Antibiotics work by
disrupting translation at site of the ribosome
Translated polypeptide coded by insulin gene is how long?
110 amino acids
Functional insulin protein 2 chains
Alpha - 21 aa’s
Beta - 30 aa’s
preproinsulin to proinsulin
pre loses signal sequence, disulfide bonds
proinsulin to insulin
C chain drops off
What is alternative splicing?
primary transcripts from same gene can be spliced in different ways to yield different mRNAs and therefore different protein products
George Beadle & Edward Tatum
- 1941 studied relationship of genes & enzymes
- examined three neurospora crassa mutants
- mutants created by UV or X-ray treatments
Wild-type characteristics
- grows on minimal medium
- able to make all the amino acids and other substances that it needs to survive
Minimal medium
support medium combined only with molecules that are necessary for the growth of wild-type individuals
Srb & Horowitz hypothesis
certain genes were involved in making each of the 3 types of enzymes
Conclusions of Srb & Horowitz
- for a mutant to grow on ornithine or citrulline it must be able to make arginine
- if a mutant is unable to grow with ornithine or citrulline added to medium (arg3) then it must have a defect in the enzyme that converts citrulline to arginine
Ornithine is a precursor to
citrulline
Citrulline is a precursor to
arginine
the function of a gene is to
determine the production of a specific enzyme (one gene one enzyme - polypeptide - …)
what does tRNA do?
enables the translation of the information in the mRNA genetic message to a polypeptide
tRNA molecules are able to
transfer amino acids from a pool of cytoplasmically situated amino acids to a growing polypeptide strand in a ribosome
tRNA is made up of
a single RNA strand ranging between 70-90 nucleotides in length
complementarity along many stretches of a tRNA molecule results in
stretches of hydrogen bonding between complementary nucleotide bases for the formation of four double-helical segments and three characteristic loops seen in all tRNA molecules
What is anticodon region of tRNA?
specific nucleotide triplet that forms complementary base-pairs with a specific mRNA codon that codes for a specific amino acid written in 3’ to 5’ direction
3’ end of tRNA
protruding amino acid attachment site that is
made up of a single stranded CCA nucleotide
terminal A point of attachment for ? when ?
an amino acid during tRNA molecule activation
aminoacyl tRNA synthetase active site recognizes
the anticodon end of the tRNA and the region of the amino acid attachment site
How many aminoacyl tRNA synthetase?
20, one for each amino acid
For proper translation tRNA anticodon pairs with the
appropriate mRNA codon
mRNA can code for
64 codons and 20 amino acids
wobble
greater flexibility for base pairing between the third nucleotide of a codon and the corresponding base of a tRNA anticodon, explains redundancy in genetic code
In eukaryotes, the initiation of translation occurs when
a translation initiation complex forms towards the 5’ cap of the mRNA and then scans the mRNA until an AUG start codon is encountered
Where will prokaryotes translation initiation complex assemble?
at one or more ribosome binding sites called Shine-Dalgarno sequence because they have no 5’ caps
Shine-Dalgarno sequences located
a few bases upstream of the translation start codon (AUG)
prokaryotes and eukaryotes basic machinery during translation
large and small subunits of the ribosome, an mRNA molecule, charged tRNA amino acids and initiation, elongation and termination factors
