Show all the types of RNA (SNO, SNRP, mi, m, si, t, r, nc others) and explain th
ID: 178882 • Letter: S
Question
Show all the types of RNA (SNO, SNRP, mi, m, si, t, r, nc others) and explain their functions in the central dogma.
Illustrate some molecular functions and catalytic activities of the tetrahymena hammer head ribozyme.
Show the peptide synthesis (peptidyl transferase) activity of domain V of 23S rRNA; A2486 in terms of the P, E, A sites along with the small subunit and mRNA.
What are intron exon borders in eukaryotic RNA?
What are the types of introns
Show RNA processing.
Show the structure of an ncRNA gene.
Show the mechanism of self splicing introns.
Compare and contrast introns to other mobile genetic elements
How might their functions relate to Chemical evolution and the modular nature of exons in Eukaryiotic proteins?
What might be the relationship between Eukariotes having modular intron/exon genes, rapid evolution and jumping genes?
Explanation / Answer
Ribonucleic acid (RNA) is the sister molecule of the DNA and synthesized from DNA. The DNA is found in the nucleus whereas the RNA in the cytoplasm. The DNA and RNA both are long chain molecules but differ mainly in two properties. The sugar molecule in the DNA is the deoxyribose sugar whereas it is ribose sugar in RNA. In DNA the nitrogen base thymine is found and it is absent in RNA and instead of it uracil is present. The thymine pairs with adenine like wise uracil also pairs with adenine.
Generally 3 types of RNA are present-messenger RNA (mRNA), transfer RNA (tRNA) and ribosomal RNA (rRNA). The DNA serves as the template for the synthesis of mRNA and this process is known as transcription. The process of the transcription is catalyzed by the enzyme RNA polymerase. The mRNA carries the genetic message from DNA to the ribosomes where the synthesis of the proteins takes place. The process of protein synthesis is known as translation.
The tRNA molecules which are specific for particular amino acids are paired with the coded nucleotide sequence of the mRNA and the proper amino acids are joined by ribosomes to form a growing polypeptide. The nucleotide sequence of the mRNA encodes the amino acid sequence in the protein. Thus, the RNA is synthesized from the DNA and the protein is synthesized from RNA. Hence, in each cell 3 complex processes of transfer of information take place are the replication, transcription and translation.
The eukaryotic DNA is well organized and some of the DNA sequences are transcribed in to non-coding RNAs. The non-coding RNAs like microRNAs tend to decrease the expression of the particular gene by the process of RNA interference. In some cases the RNAs do not code for any protein and become silent which is known as RNA silence.
The RNA polymerase II is located in the nucleoplasm. It synthesizes the mRNA precursors and small nuclear RNAs that are involved in the splicing mechanisms. RNA polymerase II contains a unique 220 kd subunit called as carboxyl terminal domain (CTD). This domain is unique because it contains multiple repeats of YSPTSPS consensus amino acid sequences.
The process of formation of mRNA (messenger RNA) from the DNA using DNA strand as template is known as transcription. The process of transcription is quite similar to the replication of DNA. The transcription is catalyzed by RNA polymerase. The genetic message is passed from DNA to ribosomes through mRNA.
Translation is the process of protein synthesis occurs at the ribosomes. The mRNA, tRNA and rRNA act together to synthesis a polypeptide through translation. The nucleotide sequence of the mRNA is the determinant of the amino acid sequence in the polypeptide.
mRNA is the messenger RNA. It passes the genetic message from the DNA to the ribosomes and plays a major role in the protein synthesis.
tRNA is the transfer RNA. Each tRNA is a specific for a specific amino acid and forms pairing with the nucleotide sequence of mRNA with correct amino acid and enables the ribosomes to join in to a growing polypeptide.
rRNA is a ribosomal RNA occurs in the ribosomes. During the synthesis of polypeptide the ribosomal RNA, the tRNA with a specific amino acid paired to nucleotide sequence of mRNA form a complex and carryout the translation process.
snRNA is the small nuclear RNA which is a catalytic component of splicing machinery. snRNP are the small nuclear ribonucleoprotein consisting of protein – RNA particles important for splicing.
Ribozymes are catalytic RNAs that participate in RNA processing through splicing mechanism. The RNA contains a free 2` OH group. This free OH group makes the RNA catalytic and self reactive to get readily hydrolyzed by alkali. The hydrolysis of RNA with alkali yields a 2`, 3` - cyclic intermediate. The RNA contains the ribose sugar that provides a free OH group for the nucleophilic attack. The 5` phosphate group of RNA is subjected to nucleophilic attack by the – oxygen molecule in presence of 5` GDP molecule yields the pppRNA (triphosphate group) and PPi (pyrophosphate).
A site is the amino acyl site occurs in the large subunit of ribosome during translation the tRNA with a specific amino acid moves and attaches in to the A site and the peptide bond takes place between the amino acids. The first amino acid relieves from the tRNA and the next amino acid enters in to the A site.
P site is the peptidyl site. During the translation initiation process the first tRNA molecule with the amino acid binds to the initiation codon of the mRNA and the tRNA occupies the P site while the larger subunit joins there to form a complex.
E site is the exit site. During translation process the tRNA with a specific amino acid pairs with the codon of mRNA at ribosome. Peptide bond form takes place between the amino acids carried by subsequent tRNAs and the previous amino acid gets relieved from the tRNA and exits through E site.
In eukaryotes, the activity promoter can be increased by Cis – acting elements called enhancers. The enhancer sequences can stimulate the promoters over a distance of several thousand base pairs. They can be located at either upstream, downstream or at the middle region of the transcribed gene. The enhancers are effective when they are located on DNA strand. The enhancers like promoters are bound to proteins and are involved in regulation of transcription.