This modification further protects the pre-
mRNA from degradation and signals the export of the cellular factors
that the transcript needs to the cytoplasm.
Why must mRNA be edited?
RNA editing in mRNAs
effectively alters the amino acid sequence of the encoded protein
so that it differs from that predicted by the genomic DNA sequence.
Why does eukaryotic mRNA need processing?
Eukaryotic mRNAs must undergo several processing steps before they can be transferred from the nucleus to the cytoplasm and
translated into a protein
. The additional steps involved in eukaryotic mRNA maturation create a molecule that is much more stable than a prokaryotic mRNA.
Why both ends of eukaryotic mRNAs must be modified?
Eukaryotic mRNA is sometimes edited or spliced before it leaves the nucleus, so
they need to regulate which mRNAs can leave the nucleus
. Moreover, translation of the instructions encoded in the mRNA is a much more highly regulated process in eukaryotes, and these modifications also play important roles in that process.
What are three ways that mRNA is edited in eukaryotes?
The pre-mRNA has to go through some modifications to become a mature mRNA molecule that can leave the nucleus and be translated. These include
splicing, capping, and addition of a poly-A tail
, all of which can potentially be regulated – sped up, slowed down, or altered to result in a different product.
What happens when you modify RNA?
One of the major impacts of RNA editing is
protein recoding
. Recoding is the process in which one or more nucleotide changes in RNA results in a different codon. This produces proteins that are different from their genetic forms and these different forms of proteins often have a modified function or structure.
How do you modify mRNA?
The pre-mRNA has to go through some modifications to become a mature mRNA molecule that can leave the nucleus and be translated. These include
splicing, capping, and addition of a poly-A tail
, all of which can potentially be regulated – sped up, slowed down, or altered to result in a different product.
Is mRNA Monocistronic in eukaryotes?
Thus some sort of regulation must exist. At least 15 different mRNAs are produced from this gene cluster. Monocistronic mRNA is a mRNA that encodes only one protein and
all eukaryotic mRNAs are monocistronic
. The development of the mature monocistronic eukaryotic transcript involves several different processing steps.
What are the 3 major steps involved in mRNA processing?
The three most important steps of pre-mRNA processing are
the addition of stabilizing and signaling factors at the 5′ and 3′ ends of the molecule
, and the removal of intervening sequences that do not specify the appropriate amino acids. In rare cases, the mRNA transcript can be “edited” after it is transcribed.
Do eukaryotes have mRNA?
When an RNA transcript is first made in a
eukaryotic
cell, it is considered a pre-mRNA and must be processed into a messenger RNA (mRNA).
What are the modifications made to eukaryotic mRNA?
Eukaryotic pre-mRNAs are modified with
a 5′ methylguanosine cap and a poly-A tail
. These structures protect the mature mRNA from degradation and help export it from the nucleus. Pre-mRNAs also undergo splicing, in which introns are removed and exons are reconnected with single-nucleotide accuracy.
What are the two main roles of the 5 cap of a eukaryotic mRNA?
The 5′ cap has four main functions:
Regulation of nuclear export; Prevention of degradation by exonucleases
; Promotion of translation (see ribosome and translation);
What are four ways that mRNA can be modified?
What are four ways that mRNA can be modified? (1)
Adding a modified guanine to the 5′ end, (2) adding a polyadenylation tail to the 3′ end, (3) splicing of introns
, and (4) RNA editing.
What is an example of transcriptional regulation?
The maltose operon
is an example of a positive control of transcription. When maltose is not present in E. coli, no transcription of the maltose genes will occur, and there is no maltose to bind to the maltose activator protein.
Where does post-transcriptional modification occur?
RNA Transport from the Nucleus to
the Cytoplasm
Post-transcriptional modifications of pre-mRNA, such as capping, splicing, and polyadenylation, take place in the nucleus. After these modifications have been completed, the mature mRNA molecules have to be translocated into the cytoplasm, where protein synthesis occurs.
Are exons genes?
An exon is
the portion of a gene that codes for amino acids
. In the cells of plants and animals, most gene sequences are broken up by one or more DNA sequences called introns.
