Translation Flashcards
Briefly state what translation is
translating the language of RNA nucleotides into the language of amino acids
What is translated?
mRNA
What is mRNA translated into?
a linear chain of amino acids
Where does translation occur?
in the cytoplasm
What makes the reactions in translation occur?
the catalytic activity of ribosomes (aka ribozymes)
What else can ribosomes be called? why?
ribozymes because they contain RNA which has catalytic activity
What is a codon? Give an example
a triplet of nucleotides in the mRNA
ex. AUG
How many amino acids does each codon code for?
one amino acid
T or F: codons can overlap
False, they are non-overlapping
T or F: the genetic code is nearly universal
True
How many codon possibilities are there?
64
Why is the genetic code redundant?
there are 64 possible codons but only 20 amino acids, so some amino acids are coded by multiple codons
What is the start codon? What does it code for?
AUG is always the first codon read from the mRNA transcript
it codes for methionine
How many start codons are there?
1
How many stop codons are there?
3
What are the stop codons? what do they code for?
UAA, UAG, UGA
they signify the end of the coding region of the mRNA and the end of the polypeptide
they DO NOT CODE FOR ANY AMINO ACID
T or F: the stop codons code for specific amino acids
FALSE
they just mean it’s the end of the mRNA transcript, no amino acid is added
Why is it critical that codons are read in the correct frame? how is the correct frame ensured?
ensured by the initiation process orienting the AUG codon in a specific position in the ribosome
crucial because if translation begins even one letter after, a completely different sequence will be translated
ex. The red dog ate the big cat –> her edd oga tet heb igc at if you start one letter later
What is main function of tRNA?
it is the molecule that translates the mRNA sequence into amino acid sequence
Describe the structure of tRNA
an RNA molecule with extensive intrachain binding which results in a cloverleaf-like structure that twists into a 3D upside down ‘L’
T or F: most tRNAs are different lengths
false, they are all about the same length (73-93 nucleotides)
Why do tRNA molecules have many unusual bases?
post-transcriptional changes like methylation
How is the ‘stem and loop’ structure of a tRNA molecule formed?
the base sequences in one part of the molecule are complementary to a nearby sequence
What is an anticodon?
a 3-letter sequence that tRNA has that is complementary and antiparallel to a codon in the mRNA