Transcription and Translation (Lec 7 & 8) Flashcards
True or False?
Genomic DNA controls protein synthesis directly
false
Transcription, simply, is….
DNA -> RNA
Translation, simply, is…
RNA -> Protein
What is mRNA?
messenger RNA - codes for proteins
what is rRNA?
ribosomal RNA, forms the basic structure of the ribosome and catalyzes protein synthesis
What is tRNA?
Transfer RNA, central to protein synthesis as adaptors between mRNA and amino acids
What is snRNA?
small nuclear RNA, function in a variety of nuclear processes, including the splicing of pre-mRNA
What is snoRNA?
small nucleolar RNA, help to process and chemically modify rRNA
What is miRNA?
MicroRNA, regulate gene expression by blocking translation of specific mRNA and cause degradation
What is siRNA?
small interfering RNA, turn off gene expression by directing the degradation of selective mRNA and the establishment of compact chromatin structure
What are the stages of prokaryotic transcription?
sigma factor attaches, sliding, closed complex forms, open compile, abortive initiation, promoter clearance and sigma factor release, elongation, termination hairpin, termination
Describe Eukaryotic Transcription initiation
begins with the binding of TFIID to the tata box via TBP, TFIIB is recruited, followed by TFIIF, RNA pol I, TFIIE, and TFIIH; all these factors join to form the transcription initiation complex; DNA unwinds and exposes template strand; RNA pol II makes short lengths of RNA; phosphyorylation of CTD by TFIIH causes the pol to leave the promoter and begin elongation
How does transcription initiation in vivo begin?
binding of general transcription factors, RNA pol, mediator, and chromatin remodeling complexes, and histone-modifying enzymes
Describe RNA processing in Eukaryotes
modification of the 5’ end of mRNA - RNA capping (7-methyl guanosine)
removal of non-coding sequences - RNA splicing (intron removal)
modification of the 3’ end of mRNA - Polyadenylation (addition of poly A tail)
What is the genetic code?
set of rules that convert the nucleotide sequence of a gene into the amino acid sequence of protein using mRNA as an intermediary
How many total codons are there and how many known amino acids are there?
61 triplet codons; 20 known amino acids
What does the adaptor hypothesis state?
the genetic code is read by molecules that can recognize a codon and carry the corresponding amino acid
What role does tRNA play as the adaptor?
binds specific codons and brings with it an AA
What is the general structure of tRNA?
cloverleaf: secondary structure of tRNA
two regions of unpaired nucleotides are crucial to the functions of tRNA
What is the anticodon loop?
one of the two regions of unpaired nucleotides: a set of 3 consecutive nucleotides that pair with a complementary codon in an mRNA molecule
What is the other region of unpaired nucleotides in tRNA that is not the anticodon loop?
3’ CCA terminal region which binds the amino acid that matches the corresponding codon
Genetic code is translated by two adaptors. What are they?
tRNA synthetase, and aminoacyl-tRNA
What is step 2 of translating mRNA?
peptidyl transferase
What are the three stop codons?
UAA, UAG and UGA
What recognizes the stop codons?
release factors
What do release factors bind to?
A site of ribosome containing the stop codon - catalyzes the addition of a water molecule instead of an amino acid
Where does the protein fold into its 3D structure?
cytoplasm, after it has been released from ribosome
