Explain how RNA is modified after transcription in eukaryotic cells?

Question

it can be short and brief

Answer 1

Post-transcriptional modifications of mRNA are:



G-capping : Addition of a 7-methylguanosine at the 5'end of the mRNA molecule. This is mediated by the Capping enzyme (linking a GMP to the 5'-terminal ribonucleotide via a 5'-5'-phosphodiester bond) and a methyltransferase which methylates the guanine at C7.



Polyadenylation: Addition of adenine residues (about 200) to the 3'end of the mRNA by polyadenylate polymerase.



Splicing: Removal of the non-coding introns from a mRNA precursor and joining together the coding exons forming the mature mRNA which serves as a template for translation. This process is mediated by the spliceosome which is a complex of snRNPs ( small nuclear ribonucleoproteins).



The function of the 5'G-cap and poly(A) tail is to stabilize mRNA and protect it against degradation by exonucleases ( which degrade unmodified RNA - e.g. of viral origin). Additionally the 5'G-cap is important for transport from the nucleus to the cytoplasm and for the initiation of translation by the ribosomes.

Splicing is required in eukaryotes to generate mature coding RNAs out of precursor RNAs which still contain noncoding regions (Introns), they need to be removed to produce the correct protein. Additionaly the splicing machinery enables a cell to produce different variants of a protein encoded by a single gene locus by alternative splicing.

Answer 2

Post Transcriptional Modifications

Answer 3

remember that enzymes are proteins so how they are made can be explained by the process of protein synthesis.



1.) The cell receives a signal that loosens the DNA and makes the wanted gene available for transcription.



2.) Transcription: The information provided by DNA is then transcribed into RNA. RNA processing takes place in the nucleus before it leaves for the cytoplasm. This RNA strand is the "messenger RNA" or mRNA for short.



3.) Translation: The mRNA then leaves the nucleus and goes through translation in the cytoplasm. Here, ribosomes meet the mRNA and translates the nucleotides into amino acids. A combination of three nucleotides (codon) = one amino acid. Remember that amino acids are the building blocks of proteins.



4.) The amino acids are then covalently bonded to one another. This produces a polypeptide, another name for protein.



5.) The polypeptide chain will then fold up to accordingly and may go to the rough ER for further modifications and/or the Golgi Body for transportation in/around/out the cell, depending on the protein's function.



After making changes to the protein in the Golgi Body, then the protein is ready to work! Enzymes vary in structure and therefore vary in their function. They can work inside the cell, or they can be secreted.



~David

Answer 4

Following transcription in eukaryotic cells, messenger RNA (mRNA) undergoes a process referred to as RNA splicing before it becomes mature mRNA and exits the nucleus. During this process, noncoding regions of RNA, referred to as introns, are excised (or removed), and the remaining coding regions (exons) are spliced together by the enzyme DNA ligase.



Note that introns are noncoding in that they do not code for the synthesis of proteins. By contrast, exons are the regions of mRNA that are actually translated into polypeptides.

Answer 5

1. Transcription of genes to mRNA. mRNA codes for proteins. every 3 bases encode for one peptide. this mRNA is then "processed" and has a cap and a tail attached to it. it then comes out of the nucleus and goes to the endoplasmic reticulum(ER). 2. Translation: in the ER, the mRNA meets the tRNA. this is where the peptides are joined together to form a polypeptide, the primary structure of a protein. the synthesis starts when the code for Methionine is encountered, so, methionine(amino acid) will be the 1st of the peptides in the chain. subsequently more amino acids are added to the chain. the chain stops growing when the tRNA encounters a stop codon. then the chain is released and carried in a vesicle to the GOLGI APPARATUS. 3. in the golgi apparatus, the chain is modified wherever necessary, i.e. formation of disulfide bonds at cys residues and the protein is folded. now the protein is synthesized and is ready to function. this is a VERY VERY brief explanation to how protein synthesis works. there are more steps involved at each stage.

Answer 6

The introns are spliced out and there is an addition of a 5'-cap and 3'-poly A tail added in most cases.

Answer 7

5' guanine cap

3' poly-A tail

Splicing out of introns / differential splicing together of exons



(and of course eventual degradation by RNA-ases)

Answer 8

I need more details

Answer 9

It depends..

Answer 10

Do your own homework -__- Go look in the book.