Lecture 15- Gene Expression Flashcards
What is the central dogma of molecular biology?
DNA → RNA → protein
What is the difference between ribose and deoxyribose?
Ribose has a 2 hydroxyl whereas deoxyribose just has a 2 hydrogen
What is the main function of mRNA?
Encodes amino acid sequence
What is the main function of rRNA?
Ribosomal composition
What is the main function of tRNA?
Carries amino acids to ribosome during translation
What is a codon?
Sequence of 3 nucleotides which code for a single amino acid
What is the start codon and which amino acid does it code for?
AUG codes for methionine
What does it mean that genetic code is degenerate/unambiguous?
Redundancy in genetic code - multiple codons code for the same amino acid
What is the start site for transcription?
Promoter (specific sequence of DNA on transcribed strand at the beginning of gene)
True or False: RNA polymerase needs an RNA primer similar to DNA replication
False; RNA polymerase does not require a primer
In which direction does RNA polymerase synthesize RNA?
5 to 3 direction
In which direction is the DNA template strand read in?
Read in 3 to 5 direction
How does RNA polymerase know when to stop transcribing?
RNA reaches termination sequence on DNA → mRNA falls off DNA template
True or False: Initiation of transcription begins with a start codon
False; initiation of transcription begins with a promoter. Initiation of translation uses a start codon
What is the name for the coding regions of mRNA?
Exons
What major structures form a ribosome?
Large and small subunit
What is the main function of aminoacyl-tRNA synthetase?
Links carboxyl group of amino acid to 3` end of tRNA (loads tRNA)
What is the function of the A-site on the large ribosomal subunit?
Arrival site for loaded tRNA
What is the function of the P-site on the large ribosomal subunit?
Holds growing polypeptide chain
What is the function of the E-site on the large ribosomal subunit?
tRNA exit site
Which enzyme is responsible for catalyzing the peptide bond between amino acids during translation?
Ribozyme
What would result if pre-mRNA failed to complete modification into a mature mRNA?
mRNA would either not proceed out of the nucleus or if it did, it would undergo degradation in the cytoplasm
Which event marks the start of translation termination?
Stop codon signals releasing factors
What happens to tRNA after it leaves the ribosome?
Binds to an aminoacyl-tRNA synthetase to be reloaded/charged
