exam 3 part 2 Flashcards
RNA capping modifies the __ end of the RNA transcript, the end that is synthesized first. The RNA is capped by the addition of an atypical ________—a ______ nucleotide bearing a ____ group(methylguanosine), which is attached to the 5 end of the RNA in an unusual way. This capping occurs after RNA polymerase II has produced about ____ nucleotides of RNA, long before it has completed transcribing the whole gene.
RNA capping modifies the 5 end of the RNA transcript, the end that is synthesized first. The RNA is capped by the addition of an atypical nucleotide—a guanine (G) nucleotide bearing a methyl group (methylguanosine), which is attached to the 5 end of the RNA in an unusual way. This capping occurs after RNA polymerase II has produced about 25 nucleotides of RNA, long before it has completed transcribing the whole gene.
When sequence called _______ signal shows up in RNA during transcription. Multiprotein in transcription termination, cuts mRNA at ‘signal’, add string (200+) of A’s to end
Polyadenylation provides a newly transcribed mRNA with a special structure at its ___ end. In contrast with bacteria, where the 3 end of an mRNA is simply the end of the chain synthesized by the RNA polymerase, the 3 end of a forming eukaryotic mRNA is first trimmed by an enzyme that cuts the RNA chain at a particular sequence of nucleotides. The transcript is then finished off by a second enzyme that adds a series of repeated adenine (A) nucleotides to the cut end.
When sequence called polyadenlation signal shows up in RNA during transcription. Multiprotein in transcription termination, cuts mRNA at ‘signal’, add string (200+) of A’s to end
Polyadenylation provides a newly transcribed mRNA with a spe- cial structure at its 3 end. In contrast with bacteria, where the 3 end of an mRNA is simply the end of the chain synthesized by the RNA polymerase, the 3 end of a forming eukaryotic mRNA is first trimmed by an enzyme that cuts the RNA chain at a particular sequence of nucleotides. The transcript is then finished off by a second enzyme that adds a series of repeated adenine (A) nucleotides to the cut end.
The_____ protect the mRNA from degrade
The A are bind to the _______ those protect the end and serves as a signal
The poly a tail protect the mRNA from degrade
The A are bind to the PABP (poly A binding protein), those protect the end and serves as a signal
The CAP increase _____, chemical ‘____’, only ______ has (____, _____ doesn’t)
The CAP increase stability, chemical ‘tag’, only mRNA has (rRNA, tRNA doesn’t)
each intron contains a few short nucleotide sequences that act as cues for its removal from the pre-mRNA. Always ____ in the _____ for ___ (match the RNA in the spliceosome). These spcial sequences are found at or ____ each end of the intron and are the same or very similar in all -_____
each intron contains a few short nucleotide sequences that act as cues for its removal from the pre-mRNA. Always A in the 20-50 for intron (match the RNA in the spliceosome). These special sequences are found at or near each end of the intron and are the same or very similar in all introns
Splicing is usually carried by ______ that includes _____ and small nuclear ________ The snRNPs recognize splice-site sequences through complementary base-pairing between their RNA components and the sequences in the pre-mRNA.
First, they loop back to ____ in intron (______ point) then the 5’ end binds to 2 ‘____ group on ____, forming a _____. Then the 3’ end is cut, 2 exons are joined
Splicing is usually carried by spliceosome that includes snRNPs: small nuclear ribonucleoproteins and small nuclear RNAs (snRNAS.) The snRNPs recognize splice-site sequences through complementary base-pairing between their RNA components and the sequences in the pre-mRNA. First, they loop back to adenine in intron (Branch point) then the 5’ end binds to 2 ‘OH group on adenine, forming a lariat. Then the 3’ end is cut, 2 exons are joined
- mRNA processing is “plastic”
- more than one signal in a transcript for:
1) 5’ cap
2) 3’ tail - the choice of cap or tail is controlled by the presence or absence of the blocking protein or they need a signal “work”
- same gene, different proteins (“isoforms”)
- mRNA processing is “plastic”
- more than one signal in a transcript for:
1) 5’ cap
2) 3’ tail - the choice of cap or tail is controlled by the presence or absence of the blocking protein or they need a signal “work”
- same gene, different proteins (“isoforms”)
Because a single mRNA molecule can be translated into protein many times, the length of time that a mature mRNA molecule persists in the cell affects the amount of protein it produces. Each mRNA molecule is eventually degraded into nucleotides by _____ (___) present in the cytosol
Because a single mRNA molecule can be translated into protein many times, the length of time that a mature mRNA mole- cule persists in the cell affects the amount of protein it produces. Each mRNA molecule is eventually degraded into nucleotides by ribonucleases (RNAses) present in the cytosol
translation
- only ______ processed mRNAs exported
- The cap and poly-A tail of a mature mRNA molecule are “_____” by proteins that recognize these modifications.
- only correctly processed mRNAs exported
- The cap and poly-A tail of a mature mRNA molecule are “marked” by proteins that recognize these modifications.
\_\_\_\_\_\_ RNA(mRNAs) code for proteins \_\_\_\_\_\_\_\_ rna(Rrna): form the core of the ribosome's structure and catalyze protein synthesis micro RNAs(miRNAs) \_\_\_\_\_\_\_\_\_ transfer RNAs(tRNAs) \_\_\_\_\_\_\_\_ other noncoding RNAs: used in RNA \_\_\_\_\_, \_\_\_\_\_\_ telomere maintenance, and many other processes
messenger RNA(mRNAs)
code for proteins
ribosomal rna(Rrna):
form the core of the ribosome’s structure and catalyze protein synthesis
micro RNAs(miRNAs)
regulate gene expression
transfer RNAs(tRNAs)
serve as adaptors between mRNA and amino acid during protein synthesis
other noncoding RNAs:
used in RNA splicing, gene regulation, telomere maintenance, and many other processes
tRNA molecules are molecular adaptors, linking amino acids to codons.
-has a set of three consecutive nucleotides that bind to the complementary codon in an mRNA molecule(_______). The other is a short _____-stranded region at the ____ end of the molecule; this is the site where the amino acid that matches the codon is covalently attached to the tRNA.
tRNA molecules are molecular adaptors, linking amino acids to codons.
-has a set of three consecutive nucleotides that bind to the complementary codon in an mRNA molecule(anticodon). The other is a short single-stranded region at the 3 end of the molecule; this is the site where the amino acid that matches the codon is covalently attached to the tRNA.
The genetic code is translated by the cooperation of two adaptors: aminoacyl-tRNA synthetases and tRNAs
aminoacyl-tRNA synthetases is an enzyme which covalently couple each amino acid to its appropriate set of tRNA molecules.
The genetic code is translated by the cooperation of two adaptors: aminoacyl-tRNA synthetases and tRNAs
The genetic code is translated by the cooperation of two adaptors: aminoacyl-tRNA synthetases and tRNAs
aminoacyl-tRNA synthetases is an enzyme which covalently couple each amino acid to its appropriate set of tRNA molecules.
Each _____ couples a particular _______ to its corresponding _______, a process called charging. The ______ on the _______ tRNA molecule then forms base pairs with the appropriate codon on the mRNA. An error in either
the charging step or the binding of the charged tRNA to its codon will cause the wrong amino acid to be incorporated into a protein chain.
Each synthetase couples a particular amino acid to its corresponding tRNAs, a process called charging. The anticodon on the charged tRNA molecule then forms base pairs with the appropriate codon on the mRNA. An error in either
the charging step or the binding of the charged tRNA to its codon will cause the wrong amino acid to be incorporated into a protein chain.
- this implies there is more than one ____ for many of the amino acids or that some _______ molecules can base-pair with more than one codon
- tRNAs are constructed so that they require accurate base-pairing only at the first two positions of the codon and can tolerate a mismatch (or ______) at the third position. This wobble base-pairing explains why so many of the alternative codons for an amino acid differ only in their third nucleotide
- Wobble base-pairings make it possible to fit the ____ amino acids to their ____ codons with as few as ____ kinds of tRNA molecules.
- this implies there is more than one tRNA for many of the amino acids or that some tRNA molecules can base-pair with more than one codon
- tRNAs are constructed so that they require accurate base-pairing only at the first two positions of the codon and can tolerate a mismatch (or wobble) at the third position. This wobble base-pairing explains why so many of the alternative codons for an amino acid differ only in their third nucleotide
- Wobble base-pairings make it possible to fit the 20 amino acids to their 61 codons with as few as 31 kinds of tRNA molecules.
Each ribosome has a binding site for mRNA and three binding sites for tRNA. The tRNA sites are designated the ___ ,___, and ___ sites (short for aminoacyl- tRNA, peptidyl-tRNA, and exit, respectively).
Each ribosome has a binding site for mRNA and three binding sites for tRNA. The tRNA sites are designated the A, P, and E sites (short for aminoacyl- tRNA, peptidyl-tRNA, and exit, respectively).
