Lecture 7 - RNA Structure & Function | Molecular Biology (DNA) by ILLL, DU - Biotechnology Engineering (BT) PDF Download

 Page 1


RNA Structure & Function 
Institute of Life Long Learning Page 0 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Paper:Molecular Biology 
Lesson: RNA Structure & Function 
Lesson Developer:  
Dr. Simran Jit 
   Dr. Nidhi Garg 
College/Dept: Zoology, Miranda House/  
Zoology, Hindu College 
Delhi University 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Page 2


RNA Structure & Function 
Institute of Life Long Learning Page 0 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Paper:Molecular Biology 
Lesson: RNA Structure & Function 
Lesson Developer:  
Dr. Simran Jit 
   Dr. Nidhi Garg 
College/Dept: Zoology, Miranda House/  
Zoology, Hindu College 
Delhi University 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
RNA Structure & Function 
Institute of Life Long Learning Page 1 
 
 
 
 
Table of Contents 
 
 
 
? Introduction  
? Structure of RNA 
? Types of RNA 
? Informational RNA: Messenger RNA (mRNA) 
? Molecular Machine: Ribosomal RNA (rRNA) 
? Adaptor Molecule: Transfer RNA (tRNA)  
? Regulatory RNA 
A. Non coding RNAs in prokaryotes 
B. Non coding RNAs in eukaryotes 
i. Small nuclear RNA 
ii. Micro RNA 
iii. Small interfering RNA 
iv. Small nucleolar RNA 
? Catalytic RNA 
? Functions of RNA 
? Storage of genetic information  
? Transfer of genetic information  
? Structural role of RNA  
? Regulatory RNA 
? Catalytic RNA 
? Summary  
? Exercise/ Practice 
? Glossary 
? References/ Bibliography/ Further Reading 
 
 
Page 3


RNA Structure & Function 
Institute of Life Long Learning Page 0 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Paper:Molecular Biology 
Lesson: RNA Structure & Function 
Lesson Developer:  
Dr. Simran Jit 
   Dr. Nidhi Garg 
College/Dept: Zoology, Miranda House/  
Zoology, Hindu College 
Delhi University 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
RNA Structure & Function 
Institute of Life Long Learning Page 1 
 
 
 
 
Table of Contents 
 
 
 
? Introduction  
? Structure of RNA 
? Types of RNA 
? Informational RNA: Messenger RNA (mRNA) 
? Molecular Machine: Ribosomal RNA (rRNA) 
? Adaptor Molecule: Transfer RNA (tRNA)  
? Regulatory RNA 
A. Non coding RNAs in prokaryotes 
B. Non coding RNAs in eukaryotes 
i. Small nuclear RNA 
ii. Micro RNA 
iii. Small interfering RNA 
iv. Small nucleolar RNA 
? Catalytic RNA 
? Functions of RNA 
? Storage of genetic information  
? Transfer of genetic information  
? Structural role of RNA  
? Regulatory RNA 
? Catalytic RNA 
? Summary  
? Exercise/ Practice 
? Glossary 
? References/ Bibliography/ Further Reading 
 
 
RNA Structure & Function 
Institute of Life Long Learning Page 2 
 
Introduction 
 
There are two chemically distinct forms of nucleic acids in the cell: ribonucleic acid 
(RNA) and deoxyribonucleic acid (DNA). Although DNA is the blue print of life, RNA 
is versatile in its function performing cellular processes such as gene expression, 
priming DNA replication, RNA processing, mRNA turnover, protein synthesis and 
protein targeting. A few types of RNA can also catalyse chemical reactions in living 
cells. RNA can also be the hereditary material as many viruses have RNA genomes 
and are either self-replicating or replicate through a DNA intermediate. Such 
predominance in cellular functions has led to the hypothesis that the pre-biological 
world was an ?RNA world,? in which RNA performed the informational function of 
DNA as well as the catalytic function of proteins.  
Unlike double helical DNA, the RNA principally exists as a single polynucleotide 
chain. Its monomer nucleotides are very similar to DNA monomer nucleotides, 
consisting of a nitrogenous base, a ribose sugar and a phosphate. 
 
RNA is transcribed from DNA by enzymes called RNA polymerases and is central to 
the synthesis of protein. Several types of RNA exist in the cell and specific functions 
are assigned to each type of RNA, mediating the flow of genetic information from 
DNA to protein. For this whole mechanism of protein synthesis, first the genomic 
DNA sequences encoding a gene product are copied into messenger RNA (mRNA) 
that binds to ribosomes in the cytoplasm. These ribosomes which are roughly half 
RNA (rRNA) and half protein, translate the information contained in mRNAs into a 
specific sequence of amino acids in a polypeptide chain. Transfer RNAs (tRNAs) 
deliver to the ribosome the appropriate amino acid via interaction of the tRNA 
anticodon with the mRNA codon. In eukaryotes, in addition to these, small nuclear 
RNA (snRNA) has a role in pre-mRNA splicing and small nucleolar RNA (snoRNA) 
has a role in rRNA processing. 
 
Value Addition: Interesting to know 
Heading text: RNA Tie Club 
Body text: Started in 1954, the club had select members who could share their 
ideas and findings not yet ripe enough to be published in scientific journals. Eight of 
these members went on to win Nobel Prizes. In 1956, one of members, Alexander 
Rich—an X-ray crystallographer and David Davies, both working at the National 
Institutes of Health, discovered that single strands of RNA can "hybridize," sticking 
together to form a double-stranded molecule. Later, in 1960, Alexander Rich, 
discovered that an RNA molecule and a DNA molecule could form a hybrid double 
helix. This was the first experimental demonstration of a way in which information 
could be transferred from DNA to RNA. 
 
Source: Author 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Page 4


RNA Structure & Function 
Institute of Life Long Learning Page 0 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Paper:Molecular Biology 
Lesson: RNA Structure & Function 
Lesson Developer:  
Dr. Simran Jit 
   Dr. Nidhi Garg 
College/Dept: Zoology, Miranda House/  
Zoology, Hindu College 
Delhi University 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
RNA Structure & Function 
Institute of Life Long Learning Page 1 
 
 
 
 
Table of Contents 
 
 
 
? Introduction  
? Structure of RNA 
? Types of RNA 
? Informational RNA: Messenger RNA (mRNA) 
? Molecular Machine: Ribosomal RNA (rRNA) 
? Adaptor Molecule: Transfer RNA (tRNA)  
? Regulatory RNA 
A. Non coding RNAs in prokaryotes 
B. Non coding RNAs in eukaryotes 
i. Small nuclear RNA 
ii. Micro RNA 
iii. Small interfering RNA 
iv. Small nucleolar RNA 
? Catalytic RNA 
? Functions of RNA 
? Storage of genetic information  
? Transfer of genetic information  
? Structural role of RNA  
? Regulatory RNA 
? Catalytic RNA 
? Summary  
? Exercise/ Practice 
? Glossary 
? References/ Bibliography/ Further Reading 
 
 
RNA Structure & Function 
Institute of Life Long Learning Page 2 
 
Introduction 
 
There are two chemically distinct forms of nucleic acids in the cell: ribonucleic acid 
(RNA) and deoxyribonucleic acid (DNA). Although DNA is the blue print of life, RNA 
is versatile in its function performing cellular processes such as gene expression, 
priming DNA replication, RNA processing, mRNA turnover, protein synthesis and 
protein targeting. A few types of RNA can also catalyse chemical reactions in living 
cells. RNA can also be the hereditary material as many viruses have RNA genomes 
and are either self-replicating or replicate through a DNA intermediate. Such 
predominance in cellular functions has led to the hypothesis that the pre-biological 
world was an ?RNA world,? in which RNA performed the informational function of 
DNA as well as the catalytic function of proteins.  
Unlike double helical DNA, the RNA principally exists as a single polynucleotide 
chain. Its monomer nucleotides are very similar to DNA monomer nucleotides, 
consisting of a nitrogenous base, a ribose sugar and a phosphate. 
 
RNA is transcribed from DNA by enzymes called RNA polymerases and is central to 
the synthesis of protein. Several types of RNA exist in the cell and specific functions 
are assigned to each type of RNA, mediating the flow of genetic information from 
DNA to protein. For this whole mechanism of protein synthesis, first the genomic 
DNA sequences encoding a gene product are copied into messenger RNA (mRNA) 
that binds to ribosomes in the cytoplasm. These ribosomes which are roughly half 
RNA (rRNA) and half protein, translate the information contained in mRNAs into a 
specific sequence of amino acids in a polypeptide chain. Transfer RNAs (tRNAs) 
deliver to the ribosome the appropriate amino acid via interaction of the tRNA 
anticodon with the mRNA codon. In eukaryotes, in addition to these, small nuclear 
RNA (snRNA) has a role in pre-mRNA splicing and small nucleolar RNA (snoRNA) 
has a role in rRNA processing. 
 
Value Addition: Interesting to know 
Heading text: RNA Tie Club 
Body text: Started in 1954, the club had select members who could share their 
ideas and findings not yet ripe enough to be published in scientific journals. Eight of 
these members went on to win Nobel Prizes. In 1956, one of members, Alexander 
Rich—an X-ray crystallographer and David Davies, both working at the National 
Institutes of Health, discovered that single strands of RNA can "hybridize," sticking 
together to form a double-stranded molecule. Later, in 1960, Alexander Rich, 
discovered that an RNA molecule and a DNA molecule could form a hybrid double 
helix. This was the first experimental demonstration of a way in which information 
could be transferred from DNA to RNA. 
 
Source: Author 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
RNA Structure & Function 
Institute of Life Long Learning Page 3 
 
 
Structure 
 
Primary Structure 
 
Similar to the structure of DNA, the monomeric unit of RNA is nucleotide. The 
nucleotide consists of three components: a nitrogenous base, pentose sugar and a 
phosphate. (Fig. 1).  
The nitrogenous bases can be of a double ring structure of nine atoms, called the 
purines or a single ring of six atoms, called the pyrimidines. The two types of 
purines are Adenine (A) and Guanine (G) and the two pyrimidines which form the 
RNA include Uracil (U) and Cytosine (C) (Fig. 2).   
RNA has two major structural differences from DNA: firstly, the pentose sugar is 
ribose, whereas DNA contains a deoxyribose sugar in which the oxygen atom is 
removed from carbon atom 2. Secondly, RNA contains uracil in place of thymine. 
RNA may also have some unusual bases.  
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 1: The nitrogenous bases - Purines (A); Pyrimidines (B) 
and (C) Pentose sugar in RNA and DNA.  
Source: http://en.wikipedia.org/wiki/Purine CC 
http://en.wikipedia.org/wiki/Pyrimidine#Nomenclature  CC 
http://upload.wikimedia.org/wikipedia/commons/d/d1/Ribose_deoxyribose.png CC 
 
The number and sequence of the ribonucleotides determines the primary structure 
of RNA. Most cellular RNA is single polynucleotide chain, although some viruses can 
have single stranded or double stranded RNA as genetic material. Some RNA 
exhibit a complex secondary structure and tertiary structure. 
Page 5


RNA Structure & Function 
Institute of Life Long Learning Page 0 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Paper:Molecular Biology 
Lesson: RNA Structure & Function 
Lesson Developer:  
Dr. Simran Jit 
   Dr. Nidhi Garg 
College/Dept: Zoology, Miranda House/  
Zoology, Hindu College 
Delhi University 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
RNA Structure & Function 
Institute of Life Long Learning Page 1 
 
 
 
 
Table of Contents 
 
 
 
? Introduction  
? Structure of RNA 
? Types of RNA 
? Informational RNA: Messenger RNA (mRNA) 
? Molecular Machine: Ribosomal RNA (rRNA) 
? Adaptor Molecule: Transfer RNA (tRNA)  
? Regulatory RNA 
A. Non coding RNAs in prokaryotes 
B. Non coding RNAs in eukaryotes 
i. Small nuclear RNA 
ii. Micro RNA 
iii. Small interfering RNA 
iv. Small nucleolar RNA 
? Catalytic RNA 
? Functions of RNA 
? Storage of genetic information  
? Transfer of genetic information  
? Structural role of RNA  
? Regulatory RNA 
? Catalytic RNA 
? Summary  
? Exercise/ Practice 
? Glossary 
? References/ Bibliography/ Further Reading 
 
 
RNA Structure & Function 
Institute of Life Long Learning Page 2 
 
Introduction 
 
There are two chemically distinct forms of nucleic acids in the cell: ribonucleic acid 
(RNA) and deoxyribonucleic acid (DNA). Although DNA is the blue print of life, RNA 
is versatile in its function performing cellular processes such as gene expression, 
priming DNA replication, RNA processing, mRNA turnover, protein synthesis and 
protein targeting. A few types of RNA can also catalyse chemical reactions in living 
cells. RNA can also be the hereditary material as many viruses have RNA genomes 
and are either self-replicating or replicate through a DNA intermediate. Such 
predominance in cellular functions has led to the hypothesis that the pre-biological 
world was an ?RNA world,? in which RNA performed the informational function of 
DNA as well as the catalytic function of proteins.  
Unlike double helical DNA, the RNA principally exists as a single polynucleotide 
chain. Its monomer nucleotides are very similar to DNA monomer nucleotides, 
consisting of a nitrogenous base, a ribose sugar and a phosphate. 
 
RNA is transcribed from DNA by enzymes called RNA polymerases and is central to 
the synthesis of protein. Several types of RNA exist in the cell and specific functions 
are assigned to each type of RNA, mediating the flow of genetic information from 
DNA to protein. For this whole mechanism of protein synthesis, first the genomic 
DNA sequences encoding a gene product are copied into messenger RNA (mRNA) 
that binds to ribosomes in the cytoplasm. These ribosomes which are roughly half 
RNA (rRNA) and half protein, translate the information contained in mRNAs into a 
specific sequence of amino acids in a polypeptide chain. Transfer RNAs (tRNAs) 
deliver to the ribosome the appropriate amino acid via interaction of the tRNA 
anticodon with the mRNA codon. In eukaryotes, in addition to these, small nuclear 
RNA (snRNA) has a role in pre-mRNA splicing and small nucleolar RNA (snoRNA) 
has a role in rRNA processing. 
 
Value Addition: Interesting to know 
Heading text: RNA Tie Club 
Body text: Started in 1954, the club had select members who could share their 
ideas and findings not yet ripe enough to be published in scientific journals. Eight of 
these members went on to win Nobel Prizes. In 1956, one of members, Alexander 
Rich—an X-ray crystallographer and David Davies, both working at the National 
Institutes of Health, discovered that single strands of RNA can "hybridize," sticking 
together to form a double-stranded molecule. Later, in 1960, Alexander Rich, 
discovered that an RNA molecule and a DNA molecule could form a hybrid double 
helix. This was the first experimental demonstration of a way in which information 
could be transferred from DNA to RNA. 
 
Source: Author 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
RNA Structure & Function 
Institute of Life Long Learning Page 3 
 
 
Structure 
 
Primary Structure 
 
Similar to the structure of DNA, the monomeric unit of RNA is nucleotide. The 
nucleotide consists of three components: a nitrogenous base, pentose sugar and a 
phosphate. (Fig. 1).  
The nitrogenous bases can be of a double ring structure of nine atoms, called the 
purines or a single ring of six atoms, called the pyrimidines. The two types of 
purines are Adenine (A) and Guanine (G) and the two pyrimidines which form the 
RNA include Uracil (U) and Cytosine (C) (Fig. 2).   
RNA has two major structural differences from DNA: firstly, the pentose sugar is 
ribose, whereas DNA contains a deoxyribose sugar in which the oxygen atom is 
removed from carbon atom 2. Secondly, RNA contains uracil in place of thymine. 
RNA may also have some unusual bases.  
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 1: The nitrogenous bases - Purines (A); Pyrimidines (B) 
and (C) Pentose sugar in RNA and DNA.  
Source: http://en.wikipedia.org/wiki/Purine CC 
http://en.wikipedia.org/wiki/Pyrimidine#Nomenclature  CC 
http://upload.wikimedia.org/wikipedia/commons/d/d1/Ribose_deoxyribose.png CC 
 
The number and sequence of the ribonucleotides determines the primary structure 
of RNA. Most cellular RNA is single polynucleotide chain, although some viruses can 
have single stranded or double stranded RNA as genetic material. Some RNA 
exhibit a complex secondary structure and tertiary structure. 
RNA Structure & Function 
Institute of Life Long Learning Page 4 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 2: Pyrimidine and purine nucleotides: A nucleotide is made 
up of three components: a nitrogenous base, a pentose sugar, and one or more 
phosphate groups. Carbon residues in the pentose are numbered 1' through 5' (the 
prime distinguishes these residues from those in the base, which are numbered 
without using a prime notation). The base is attached to the 1' position of the 
ribose, and the phosphate is attached to the 5' position. When a polynucleotide is 
formed, the 5' phosphate of the incoming nucleotide attaches to the 3' hydroxyl 
group at the end of the growing chain. Two types of pentose are found in 
nucleotides, deoxyribose (found in DNA) and ribose (found in RNA). Deoxyribose is 
similar in structure to ribose, but it has an H instead of an OH at the 2' position. 
Bases can be divided into two categories: purines and pyrimidines. Purines have a 
double ring structure, and pyrimidines have a single ring. 
Source: http://cnx.org/contents/62f1d705-3f65-491e-af8e 
506fd89379f6@1/Biological_Macromolecules:_Nuc CC 
 
Secondary & Tertiary Structure 
 
Based on the composition, RNA molecules are capable of intra-strand base pairing 
leading to diverse secondary and tertiary structures of RNA. In regions where 
purine pyrimidine pairing takes place, adenine pairs with uracil and guanine pairs 
with cytosine. The single RNA strand is folded upon itself, either entirely or in 
certain regions. In the folded region, majority of the bases are complementary and 
are joined by hydrogen bonds. This helps to stabilize the molecule. In addition to 
conventional Watson–Crick base pairs, RNA double helices often contain non-
Watson–Crick base pairs, most common being GU, and GA. Additionally, base 
triplets are a regular feature wherein the third base can interact in a variety of 
unconventional ways (Fig. 3). Such interactions are important mediators of RNA