Zaidi Molecular Review Flashcards
MRNA function
Code for proteins
rRNA function
Form the basic structure of the ribosome and catalyze protein synthesis
tRNA function
Central to protein synthesis as adaptor between mRNA and amino acids
SnRNAs
Function in a variety of nuclear processes, including the splicing of pre mRNA
SnoRNA function
Help to process and chemically modify rRNA
MiRNA funtion
Regulate gene expression by blocking translation of specific mRNAs and cause their degradation
SiRNAs
Turn off gene expression by directing the degradation of selective mRNAs and the establishment of compact chromatin structures
How does eukaryotic transcription initiation step begin?
The binding of TFIID to the TATA box (causes distortion in DNA)
What is the subunit called of TFIID that recognizes TATA?
TATA-box-binding-protein (TBP)
What all factors join to form the transcription initiation complex?
TFIIB, TFIIF, RNA Pol II, TFIIE and TFIIH
What factor unwinds the DNA double helix and exposes the DNA template strand during initiation?
TFIIH
What causes the polymerase to leave the promoter during initiation to begin elongation?
Phosphorylation of CTD by TFIIH
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 (addiction of poly A tail)
What is the genetic code
A set of rules that convert the nucleotide sequence of a gene into the amino acid sequence of a protein using mRNA and an intermediary
The sequence of nucleotides in the mRNA molecule is read consecutively in groups of what ?
Three (codons)
Each codon specifies either ____________ or ____________
One amino acid or a stop to the translation process
A total of _____ triplet codons code for the 20 known amino acids, thus the code is __________.
61 - degenerate
The adaptor hypothesis
Postulates that the genetic code is read by molecules that can recognize a codon and carry the corresponding amino acid.
What is the general structure of tRNA
Cloverleaf secondary structure of tRNA. It folds up into a defined 3D structure and contains 4 short double-helical segments
Two regions of unpaired nucleotides are crucial to the functions of tRNA - what are they?
- Anticodon loop - a set of 3 consecutive nucleotides that pair w/ a complementary codon in an mRNA molecule
- 3’ CCA terminal region which binds the amino acid that matches the corresponding codon
Genetic code is translated by 2 adaptors , what are they?
- ACC tRNA
2. Aminoacyl-tRNA
