L10 RNA Flashcards
What is the priamry structure of RNA?
A linear sequence of nucleotides that are linked together by phosphodiester bond
With RNA, Adenine pairs to _______; guanine pairs to ______.
Uracil; Cytosine
What is the secondary structure of RNA?
RNA is a single strand, but has regions of helical secondary structure (t-RNA): A single helix of sugar phosphates with bound nucleobases.
Stem-loop (or hairpin loop) with intramolecular base pairing between bases within the same chain that DOES NOToccur for the whole length of the molecule
True or false?
The secondary structure of RNA occurs the whole length of the molecule.
False.
It DOES NOT occur for the whole length of the molecule
It occurs when two regions of the same strand are complementary in nucleotide sequence when read in opposite directions
What is the tertiary structure of RNA?
the three-dimensional arrangement of RNA building blocks, which include helical duplexes, triple-stranded structures, and other components that are held together through connections collectively termed RNA tertiary interactions.
The 3 types of RNA are:
- Messenger RNA (mRNA)
- Ribosomal RNA (rRNA)
- Transfer RNA (tRNA)
What is the function of mRNA?
mRNA: Relay the code for a protein from DNA to the protein production site, ribosomes.
What is Ribosomal RNA?
rRNA: Present in ribosomes. Important both structurally and catalytically
What is Transfer RNA?
tRNA: The adapter unit linking the triplet code on mRNA to specific amino acids
True or False?
A tRNA having a particular anticodon will NOT always have the same amino acid attached to it.
False.
A particular anticodon WILL ALWAYS have the same amino acid attached to it.
True or False?
Base pairs to the complementary triplet code are on m-RNA (the codon).
True
True or False?
Anticodon contains 3 bases that are specific for the attached amino acid.
True
The copying of the genetic code from DNA for a specific protein is called ________.
Transcription
Translation equals _______.
Protein synthesis
True or False?
rRNA is the major component, making up two thirds of the ribosome’s mass
True.
There are two subunits of to the mammalian ribosome, known as ________ and _________.
known as the 60S (tRNA binding site) and 40S (mRNA binding site)
True or False?
During RNA translation, as rRNA travels along mRNA, it reveals the triplet codes on mRNA all at once.
False.
the triplet codes on mRNA are revealed one by one
During translation The peptide chain created so far is attached to a tRNA which is bound to the _____site. The ______site is for an incoming tRNA.
P site; A site
The triplet code ______ is revealed along with A site which accepts ONLY _______________ capable of base-pairing and bringing the amino acid His
CAU; tRNA having the necessary anticodon (GUA)
True or false?
A tRNA having a particular anticodon has the same amino acid attached to it.
True
What happens after the tRNA gives its amino acid?
The peptide chain is transferred to His and The tRNA occupying the P site now departs
What happens after The tRNA occupying the P site departs?
The Ribosome shifts along mRNA to reveal the next triplet - translocation
_________ are Significantly involved in mRNA processing and gene regulation
Small Nuclear RNA (snRNAs)
After transcription, mRNA molecules are frequently modified before translation takes place by excising a middle section known as an _______.
Intron
What splices together the End regions (exons) after introns are removed?
An snRNA/protein complex called a spliceosome
How are introns removed from mRNA?
Introns are removed by the activity of Small nuclear ribonucleoproteins (snRNAs) that align with the target mRNA by base pairing to it.
Steps:
- the pre-mRNA is cut at the 5’ splice site (the junction of the 5’ exon and the intron). The 5’ end of the intron is then joined to the branch point within the intron, generating the lariat-shaped molecule characteristic of the splicing process
- the 3’ splice site is cut, and the two exons are joined together, and the intron is released.
True or False?
The splicing machinery must be able to recognize splice junctions (i.e., the end of each exon and the start of the next) in order to correctly cut out the introns and join the exons to make the mature, spliced mRNA.
True
What signals indicate where an intron starts and ends?
The base sequence at the start (5’ end also called the donor site) of an intron is GU while the sequence at the 3’ end (a.k.a. acceptor site) is AG.
There is also a third important sequence within the intron, called a branch point, that is important for splicing.
What is alternative splicing?
Many pre-mRNAs have a large number of exons that can be spliced together in different combinations to generate different mature mRNAs.
Allows for the production of many different proteins using relatively few genes by combining different exons during splicing, create many different protein coding messages from a single RNA
What is the capping step of mRNA processing and what does it accomplish?
In the capping step of mRNA processing, a 7-methyl guanosine is added at the 5’ end of the mRNA.
The cap protects the 5’ end of the mRNA from degradation by nucleases and also helps to position the mRNA correctly on the ribosomes during protein synthesis.
The initial product of transcription of a protein coding gene is called _______.
pre-mRNA
True or False?
Both prokaryotes and eukaryotes process their ribosomal and transfer RNAs.
True
The major difference in RNA processing between prokaryotes and eukaryotes, is in _______.
the processing of messenger RNAs
In prokaryotes, the mRNA is translated __________.
directly as it comes off the DNA template
In eukaryotic cells, RNA synthesis, which occurs in the ______, and is _______ the protein synthesis machinery, which occurs in the ________.
nucleus; separated from; cytoplasm
True or false?
Prokaryotic genes have introns, noncoding regions that interrupt the gene’s coding sequence.
False.
Only eukaryotic cells have introns
The process of removing the introns and rejoining the coding sections or exons, of the mRNA, is called _______.
Splicing
The mRNA copied from genes containing introns will _______ regions that interrupt the information in the gene.
Have
These regions that must be removed before the mRNA is sent out of the nucleus to be used to direct protein synthesis are called ______.
Introns
What has to occur before a pre-mRNA can be sent out of the nucleus?
It has to be capped, spliced and had a polyA tail added.
