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RNA_ Structure-WPS Office.pptx
- 1. RNA: Structure andit's types Made by : Anshul Sethi Roll no : 614/20 Biotech(hons) 1st year
- 2. Introduction • Ribonucleic acidis a single-stranded nucleic acid found in all living cell. • Just like DNA it is also an information carrier which contains the information of synthesis of protein. • RNA molecules perform a variety of roles in the cell but are mainly involved in the process of protein synthesis (translation) and its regulation.
- 3. Occurrence • In aprokaryotic cell whole of the RNA is found in the cytoplasm because there is no nucleus. • In a Eukaryotic cell RNA is mainly found in free in the cytoplasm and within the ribosomes and also in the nucleolus. • It can be also present in mitochondria chloroplast and in some plant virus and animal virus as a hereditary material.
- 4. Structure • RNA moleculeis a single chain of ribonucleotide arranged in a linear sequence and connected together by 3'to 5' phosphodiester bonds. • A ribonucleotide contain three parts
- 5. • Adenine ,guanine,cytosine and uracil are the four nitrogen bases present in the RNA molecule. • In a RNA the phosphate group at 5' position of sugar molecule in one ribonucleotide is joined to the sugar molecule of the next ribonucleotide at 3' position by phosphodiester Bond. • This forms a backbone of alternating sugar- phosphate-sugar molecule. • The nitrogen base molecules are joined to the sugar molecule at C-1' position of this backbon by glycosidic Bond.
- 6. Nucleoside = Nitrogenbase + Pentose sugar Ribonucleoside = Nitrogen base + Ribose sugar
- 7. Nucleotide is abasic unit of nucleic acid. Nucleotide=N-base+pentose sugar+ phosphate group Ribonucleotide=N-base+ribose sugar+phosphate
- 8. 1.The pentose sugarpresent in DNA is deoxyribose. 1.The pentose sugar present in RNA is ribose. 2.Contain cytosine , thymine as pyrimidine base and adenine , guanine as purine base. 2.Contain cytosine , uracil as pyrimidine base and adenine , guanine as purine base. 3.It is a double chain of polynucleotide. 3.It is a single chain of polynucleotide. 4.It can replicate itself. 4.It cannot replicate itself. 5.It is genetic material for all living organisms. 5.It is genetic material for some plant and animal virus. 6.Mainly occur in the nucleus as main constituent of chromosome 6.Mainly occur in cytoplasm and it is the main constituent of ribosomes.
- 10. Genetic RNA • WhenRNA acts as a genetic material in an organism, then it is called Genetic RNA. • It is only found in plant and animal virus which is hereditary in the absence of DNA. • It can be double or single-stranded. Replication of Genetic RNA 1. Replication of RNA in Retroviruses (Viruses follow reverse transcription) ticle enters the host cell, ◆Viruses having RNA as the hereditary material possess an enzyme called reverse transcriptase.
- 11. ◆When a virusparticle enters the host cell, its RNA released in the host cytoplasm. ◆ Here, with the help of reverse transcriptase strand of complementary DNA is synthesised using RNA as template. ◆This single DNA strand synthesis complementary antiparallel strand completing the formation of double- stranded DNA. ◆This viral DNA then joins the DNA of host cell becoming its integral part. ◆The integrated DNA copy with host DNA is called provirus DNA and this process of DNA transcription is called reverse transcription.
- 12. ◆Utilising synthetic machineryhost cell, this DNA produces several copies of RNA and protein molecules to be used in the formation of protein coat. 2. Replication of RNA in RNA-RNA viruses ◆These viruses synthesise new genomic RNA on RNA template with the help of te enzyme called replicase. ◆These new RNA molecules then synthesise mRNAs Whiel guide synthesis of viral proteins using host's ribosomes, tRNA, amino acids and required enzymes.
- 13. Non genetic RNA •The organisms which have DNA as their hereditary material the all types of RNAs present in that organism are non genetic. • Cell access the information stored in DNA by creating RNA to direct the synthesis of proteins by the process of translation.
- 14. Messenger RNA orNuclear RNA • In 1961 two french scientists Jacob and Monad hypothesis the existence of a intermediary between DNA and its product which they named as mRNA. • All the genetic information is stored in the DNA so messenger RNA carries that information from the DNA of the nucleus to the ribosomes of the cytoplasm in which the proteins are synthesized on the basis of this information. Messanger RNA or Nuclear RNA
- 15. Characteristics of mRNA 1.Itis synthesized as a complementary strand on the DNA template(3'to5' stand). 2.It contains same complementary base arrangement of the DNA from which it is copied except that thymine of DNA is substituted by uracil. 3.In all the Eukaryotic cells the hetrogenous RNA(hnRNA) is formed first which is a precursor of the actual mature mRNA. 4.The information present on the Eukaryotic genes are always in segments .
- 18. 13.For each polypeptidechain there is only one mRNA is used. 14.Life span of mRNA in prokaryotes like Bacteria is 2 minutes whereas in eukaryotic mRNA is more stable and able to survive for hours .
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- 20. 1.CAP Region - ◆Itis a methylated region made up of 7,methyl guanosine at 5'end. ◆It provides stability to mRNA 2. Coding Region - ◆It is the region where all the information for protein chain synthesis is coded. ◆It has generally 1500 nucleotide (depending upon which protein has to be synthesized. (a) Initiation codon ◆The coding region always begins with AUG code which codes for the initiation of the protein synthesis. ◆It codes for methionine amino acid.
- 21. (b)Stop /Terminating Codon- ◆At the end of coding region UAA or UAG or UGA codon is present which when read by ribosome the protein synthesis stops that's why it is known as "Stop" codon. ◆It does not code for any amino acid. 3. Poly-A Tail - ◆It contain polyadenylic acid sequence or poly adenine nucleotide. ◆It protects the mRNA from degradation. 4. UTR( Untranslated regions ) - ◆Present just after G-Cap . ◆Helps mRNA to bind with ribosomes. 5. NCR( Non coding region) - ◆Present before the Poly-A tail which act as cellular regulator.
- 22. Tranfer RNA(tRNA) • TransferRNA (tRNA) is a small type of stable RNA that carries an amino acid to the corresponding site of protein synthesis in the ribosome. • It is also termed as soluble RNA and it constitute 10- 15% of the total RNA. Transfer RNA(tRNA)
- 23. Characteristics of tRNA 1.Itis the smallest of all other RNAs having 75-95 nucleotide . 2.The polynucleotide chain of the tRNA has hydroxyl ion at 3' end and phosphate at 5'end. 3.Due to the internal complementary base pairing, the polynucleotide chain of the tRNA undergoes secondary and tertiary folding. 4.as a result tRNA molecule acquires L shape 3D configuration which resembles twisted cloverleaf.
- 24. 5.The 3' endof the polynucleotide chain of the tRNA is called acceptor end as it is the attachment site for amino acid. 6.In 1965,R.W.Holley proposed cloverleaf model of tRNA .
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- 26. Acceptor arm orAmino acid arm
- 27. Anticodon arm • Itis a loop like structure containing anticodon sequence nucleotide that are complementary to triplet codon of the mRNA molecule. • It lies opposite to the Amino acid arm. • Since the base triplet on mRNA chain is called codon, its complementary base triplet on tRNA molecule is termed as anticodon. • function of anticodons is to bring together the correct amino acids to create a protein, based on the instructions carried in mRNA.
- 28. DHU arm (Dihydrouridinearm) • It has stem formed of 5 base pair and D loop made up of about 10 nucleotides. • It contain modified ribonucleotide dihydrouridine in the D loop derived from uridine. • The main function of D loop is recognization of amino acid
- 29. TΨC Arm orTΨCG arm • It contains modifed ribonucleotide pseudouridinylate and ribothymidylate. • It's stem contains 5 base pairs and terminal loop contains 7 nitrogenous base with a specific sequence of T(Ribothymidine),. P(Pseudouridine),C(Cytosine), G(Guanine). Variable arm .It contain 4-21 nucleotide. •It helps in stability of tRNA.
- 30. Unusual Base pairsin tRNA • Addition to the usual bases of RNA( A,U,G,C) there are some additional unusual base pairs are also present in tRNA. • For example : DHU(Dihydrouridine),T(Ribothymidine),Pseudo uridine etc. • Q.what is the role of unusual base pairs? • Ans-Prevents intramolecular base pairing in the open tRNA loop.
- 31. Structures of unusualbase pairs
- 32. Ribosomal RNA (rRNA) •It is the most common type of RNA found in the cell. • It constitutes 70 to 80% of total cellular RNA. • It is found in ribosomes. • The rRNA ensures the proper alignment of the mRNA, tRNA, and the ribosomes. Structure of rRNA • It has 3D structure formed by folding and complementary base pairing.
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- 34. • In eukaryotes80s ribosomes are present having 60s as larger ribosomal subunit and 40s as smaller ribosomal subunit. • 60s that is larger subunit of the eukaryotic ribosome is made up of 28s and 5.8s rRNA molecules. • 40s that is smaller subunit of the eukaryotic ribosome is made up of 18s rRNA molecules. •rRNA is differ in base composition from tRNA and mRNA. •rRNA is relatively richer in guanine and cytosine. Base composition of rRNA
- 35. Other types ofRNA 1.Small nuclear RNAs(snRNAs)- ◆These are small RNA molecules found in nucleus of eukaryotic cell. ◆They are formed of 100-215 nucleotide 2.Genetic RNA - ◆In some viruses RNA is genetic material which carries hereditary information. 3.Enzymatic RNA or Ribozyme - ◆Ribozymes (ribonucleic acid enzymes) are RNA molecules that have the ability to catalyze specific biochemical reactions, including RNA splicing
- 36. Functions of RNA 1.Facilitatethe translation of DNA into proteins 2.Functions as an adapter molecule in protein synthesis 3.Serves as a messenger between the DNA and the ribosomes. 4.Promotes the ribosomes to choose the right amino acid which is required in building up of new proteins in the body. 5.It serves as the genetic material in some organisms (viruses).
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