Translation Of M Rna The In Trons example essay topic

Introns and Exons March 31 1997 AP. Biology essay The finding of the Introns and the eons was one of the most significant discoveries in genetics in the past fifteen years. split genes were discovered when lack of relation between DNA sequences were seen during. DNA- mRNAhybridation. For all new m RNA, they must be transcribed by RNA polymerase enzymes. The transcription begins at the promoter sequence on the DNA and works down, thus the nucleotide sequence of the m RNA is complimentary to the one of DNA.

In eukaryotes the m RNA is processed in the nucleus before transport to the cytoplasm for translation. In order for the m RNA to become true functioning RNA it must under go several stages of modification. At first, when the m RNA is produced, a cap is added enzymatically to the 5^1 end of the RNA by linking a 7- residue by a tri phosphate bond this is called the G-cap. The G-cap is necessary for translation. The subunit of the ribosome recognizes the G-cap and then finds the initiation codon to start translation. As the m RNA comes finishes transcription, the Poly A tail is added to the 3^1 end.

As the two ends are placed the m RNA becomes pre-m RNA. The pre-m RNA consists of splicing and non-coding regions. pre-mRNA molecules are much longer than the m RNA molecule needed to code for its protein. The regions that do not code for amino acids; aa, are scattered all along the coding region. The genes are split with coding regions, called eons, short for expressed regions; in between the eons the non-coding region called. Before the translation of m RNA the in trons must be spliced off. Splicing is an complicated process for the cell.

It must locate every in tron in the primary transcript. An average m RNA consists of eight to ten in trons, some even contain sixteen in trons. eons, like in trons are also spread apart. Some of their codons may be split by in trons, so information for a single amino acid could be some distance apart. Splicing takes place in the nucleus but also could take place in the cytoplasm and the mitochondria. After the splicing of the in trons, the G-caps and the Poly A tails remain on the m RNA. A single gene can code for multiple proteins by alternative splicing.

Single strand was found to be coding for twenty different proteins, depending on how the eons are assembled. Different splicing combinations are regulated in tissue specific manner. Most of the transcribed DNA are in trons. ninety nine percent of the information contained in the gene transcript is destroyed when the in trons are eliminated since eons are only translated. Most genes have in trons.

Only ah and full of organisms are found without in trons. Larger eukaryotes tend to have bigger and more numerous amounts of in trons compared to smaller eukaryotes. There are sequence of nucleic acids at the exon-in tron junction of mRNA allowing in tron splicing., From what is known there is an GU at the 5^1 splice site and AG at the 3^1 splice site for most genes. This is called the GU-AG rule Splicing enzymes recognize these sites with the help of calledsnRNP or slurps. slurps are formed by small nuclear RNA fragments of less than three hundred nucleotides called snRNAs. As an RNA molecule is being transcribed, four slurps attach to it combining into a large.

The abundant snRNAs catalyze the cutting and the splicing of the gene. In a self splitting in tron, the hair pin structure brings the ends o near to the branch point. Then the in trons it self catalyze the making of the loop joining the two eons. The difference between self splicing intro nand one which require the is that the non-self splicing in trons can split any in trons, almost any size. This helps the organism to survive mutations.

When a mutation forms, some times the self splicing in trons lose it^1^1's hairpin structure not allowing it self to be spliced off.