RIBONUCLEIC ACID

(RNA)

Lini Cleetus C1st M.Sc BPS

CBPST, KOCHI

What we will be discussing?Nucleic acidsNucleotidesNucleosideNitrogenous basesPentose sugarDNA and RNARNAIntroductionDifferent types & functions

Conclusion

Nucleic AcidsNucleic acids are polymers of nucleotidesThey include DNA(deoxyribonucleic acid) and RNA(ribonucleic acid); -which are found in living systems

RNA

Nucleotide

PURINES PYRIMIDINES RIBOSE DEOXYRIBOSE

NITROGENOUS PENTOSE PHOSPHATE BASES SUGAR GROUP

Nucleosides

A nitrogenous base(purine or pyrimidine)

bound to a pentose sugar(ribose or

deoxyribose)

Example:

adenosine or deoxyadenosine

Guanosine or deoxyadenosine

Cytidine or deoxycytidine

Uridine or deoxythymidine

Nitrogenous bases

Cytosine(C) Thymine(T) Uracil(U)

Adenine(A) Guanine(G)

Pyrimidines

Purines

Pentose sugars

PRIMARY STRUCTURE OF NUCLEIC ACIDS

N-Glycosidic linkages

Structure of nucleic acids Back bone is sugar and phosphate group

Nitrogenous bases linked to sugar moiety project from the backbone

Nitrogenous bases are linked to pentose sugar through N-glycosidic linkage to form a nucleoside

Phosphate group is linked with 3’OH of nucleoside through phosphoester linkage

2 nucleotides are linked through 3’-5’-

phosphodiester linkage to form a

dinucleotide

More and more such groups will be linked to form

a poly nucleotide chain

Such a polymer has a free phosphate moiety at 5’

end of ribose sugar and it is called as 5’-end of

polynucleotide chain

At other end, ribose has free 3’-OH group which

is called as the 3’-end of polynucleotide chain

In RNA, every nucleotide has an additional-OH

present at 2’-position of ribose

DNA and RNA

DNA and RNADNA contains the sugar deoxyribose, while RNA contains the sugar ribose

DNA is a double stranded molecule while RNA is a single stranded molecule

DNA is stable under alkaline conditions while RNA is not stable

DNA and RNA perform different functions in humans. DNA is responsible for storing and transferring genetic information while RNA directly codes for amino acids and as acts as a messenger between DNA and ribosomes to make proteins

DNA and RNA base pairing is slightly different, since DNA uses the bases adenine, thymine, cytosine, and guanine; RNA uses adenine, uracil, cytosine, and guanine. Uracil differs from thymine in that it lacks a methyl group on its ring

Ribonucleic acid Ribonucleic acid, or RNA is one of the major biological macromolecules that are essential for all known forms of life (along with DNA and proteins) Each nucleotide in RNA contains a ribose sugar, with carbons numbered 1' through 5'. A base is attached to the 1' position, in general, adenine (A), cytosine (C), 

guanine(G), and uracil (U).

Structure of RNA

SynthesisSynthesis of RNA is usually catalyzed by an enzyme—RNA polymeraseBy using DNA as a templateThe process is known as transcriptionThere are also a number of RNA-dependent RNA polymerases that use RNA as their template for synthesis of a new strand of RNAA number of RNA viruses (such as poliovirus) use this type of enzyme to replicate their genetic material

Types of RNATransfer RNA (tRNA)

Ribosomal RNA (rRNA)

Messenger RNA (mRNA)

Messenger RNA (mRNA) Messenger RNA (mRNA) carries

information about a protein sequence to the ribosomes, the protein synthesis factories in the cell

It is coded so that every three nucleotides (a codon) correspond to one amino acid

. In eukaryotic cells, once precursor mRNA (pre-mRNA) has been transcribed from DNA, it is processed to mature mRNA

This removes its introns—non-coding sections of the pre-mRNA

The mRNA is then exported from the nucleus to the cytoplasm, where it is bound to ribosomes and translated into its corresponding protein form with the help of tRNA

Transfer RNA (tRNA)Transfer RNA (tRNA) is a small RNA chain of about 80 nucleotides It transfers a specific amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation It has sites for amino acid attachment and an anticodon region for codon recognition that binds to a specific sequence on the messenger RNA chain through hydrogen bonding

Ribosomal RNA (rRNA)Ribosomal RNA (rRNA) is the catalytic component of the ribosomes Eukaryotic ribosomes contain four different rRNA molecules: 18S, 5.8S, 28S and 5S rRNA Three of the rRNA molecules are synthesized in the nucleolus, and one is synthesized elsewher. In the cytoplasm, ribosomal RNA and protein combine to form a nucleoprotein called a ribosome The ribosome binds mRNA and carries out protein synthesis Several ribosomes may be attached to a single mRNA at any time.Nearly all the RNA found in a typical eukaryotic cell is rRNA.

D Dobbs ISU - BCB 444/544X: RNA Structure Prediction

RNA types & functions Types of RNAs Primary Function(s)

mRNA - messenger translation (protein synthesis) regulatory

rRNA - ribosomal translation (protein synthesis) <catalytic>

t-RNA - transfer translation (protein synthesis)

hnRNA - heterogeneous nuclear

precursors & intermediates of mature mRNAs & other RNAs

scRNA - small cytoplasmic signal recognition particle (SRP)tRNA processing <catalytic>

snRNA - small nuclear snoRNA - small nucleolar

mRNA processing, poly A addition <catalytic>rRNA processing/maturation/methylation

regulatory RNAs (siRNA, miRNA, etc.)

regulation of transcription and translation,

L Samaraweera 2005

RNA genomes

Like DNA, RNA can carry genetic

information. RNA

viruses have genomes composed of RNA that

encodes a number of proteins. The viral genome

is replicated by some of those proteins, while

other proteins protect the genome as the virus

particle moves to a new host cell.

Double-stranded RNA

Double-stranded RNA (dsRNA) is RNA with two

complementary strands, similar to the DNA

found in all cells. dsRNA forms the genetic

material of some viruses (double-stranded RNA

viruses)

Double-stranded RNA

ConclusionRNA is one of the major biological macromolecule essential in all life formsRibose is the sugar unit present in itGuanine ,adenine, uracil and cytisine are the nitrogenous bases present in RNAThere are different types of RNA:- mRNA, tRNA, RrnaLike DNA,RNA also can behave as a genetic material

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