This document provides information about transcription and the different types of RNA. It begins with an outline of the topic, which includes messenger RNA (mRNA), transfer RNA (tRNA), ribosomal RNA (rRNA), and microRNA (miRNA). The document then discusses each type of RNA in more detail, describing their structure, function, and role in protein synthesis. mRNA carries DNA's genetic code from the nucleus to the cytoplasm. tRNA transports amino acids to the ribosome during protein assembly. rRNA forms the ribosome where protein synthesis occurs. miRNA regulates gene expression at the post-transcriptional level.

2. Group

3. Roll no. 13 to 23
Section: A DPT
Physiology Presentation
> In respect of Dr.
Muzna Munir

4. Maryam Nadeem

5. TOPIC OUTLINE
 Transcription
 Types of RNA
Messenger RNA(mRNA)
or Codons
Transfer RNA (tRNA)
or Anticodons
Ribosomal RNA (rRNA)
MicroRNA (miRNA)
or Noncoding RNA

6. Deoxyribonucleic acid, a self replicating material
which is present in nearly all living organisms as the
main component of chromosomes. It is the carrier of
genetic information.

7. Transcription
Transcription is the first
step of gene expression,
in which a particular
segment of DNA is
copied into RNA by an
enzyme RNA
polymerase.

8. RNA Polymerase
o Also known as DNA-dependent RNA polymerase
o In process of Transcription
o essential to life and are found in all organisms and
many viruses.

9. DNA Code transfer
into cytoplasm-
Transcription…

10. Location of DNA

11. DNA used to Make Proteins

12. DNA
CODE IN
THE CELL
NUCLEUS
Introduction

13. Syeda Faiqa Rehman

14. What is DNA?
 DNA is (deoxyribose nucleic acid) a molecule that
encodes the genetic instructions used in the
development and functioning of all living organism.
 DNA is a self replicating material which is present in
nearly all living organisms as a main constituent of
chromosomes.
 In one chromosomes 25000 genes are present.
 The thickness of DNA is almost 2nm.
 10 base pairs are present in one turn.
 The length of one turn of DNA is 3.4 nm.

15. DNA Composed
of:
1.nitrogeno
us bases
2.phosphate
group
3.deoxyribo
se sugar

16. Location of DNA:
DNA is located in the nucleus of the cell .yet most of the functions
of the cell are carried out in the cytoplasm, there must be some
means for the DNA genes of the nucleus to control the reactions of
the cytoplasm. This is achieved through the intermediary of
another type of nucleic acid, RNA, the formation of which
controlled by DNA of the nucleus. thus figure shown the coding of
DNA coded information into RNA coded information this process
called transcription. the RNA in turn diffuses from the nucleus
through pores into cytoplasmic compartment, where it control
protein synthesis.

17. TRANSCRIPTION:
In transcription process the firstly combination of ribose nucleotides with
strand of DNA to form a molecule of RNA that carries the genetic code from the
gene to the cytoplasm. The RNA polymerase enzyme moves along the DNA
strand & builds the RNA molecule.

18. Synthesis of
RNA:
Temporarily
uncoiling of
DNA.
During synthesis of RNA the two
strands of DNA molecule separate
temporarily; one of these strands
use for synthesis of RNA molecule.
TRIPLET CODES:
The genetic code in which a
sequence of three nucleotides on
DNA molecule codes for template
strand whose complementary RNA
strand is formed.

19. Basic building
block of RNA:
RNA composed of
:
Ribose sugar
Thymine is
replaced by uracil
RNA is single
stranded structure.

20. Formation of
RNA
nucleotides:
RNA contain four
types of
nucleotides:
Adenine
Guanine
Cytosine
Uracil

21. Difference between DNA and RNA
DNA RNA
DNA is a deoxyribonucleic acid. RNA is ribonucleic acid.
DNA is a double helix molecule. RNA is single helix molecule.
DNA contain two polynucleotide chain. RNA contain one poly nucleotide chain.
DNA is present only in nucleus. RNA is present in whole of the cell in
the cytoplasm as well as in nucleus.
DNA contain A,C,G,T. nitrogenous
bases.
RNA contain A,T,C,U nitrogenous
bases.
DNA act as hereditary material in all
organism.
RNA act as a hereditary material in
some viruses.
DNA has no types. RNA has three types MRNA, RRNA,
TRNA.

22. Hafiza Natasha Hira

23. In The Synthesis of RNA the
activation is done by an
enzyme which is called “RNA
Polymerase”.
Activation
of the RNA
Nucleotides.

24. TRANSCRIPTION:
The process in which genes of DNA i.e., DNA code is expressed in the form of
mRNA is called Transcription. DNA is responsible for this process.

25. It is an enzyme that
catalyses the formation of
RNA from DNA strand
during transcription.
It is also called
“Transcriptase”
RNA
POLYMERASE

27. STEP 01:
In the DNA strand immediately
ahead of the initial gene is a
sequence of nucleotides called
promoter. The RNA polymerase
has an appropriate
complementary structure that
recognizes this promoter and
becomes attached to it.
STEPS Involved in
TRANSCRIPTION

28. After the RNA polymerase attaches
to the promoter the polymerase
causes unwinding of about two
turns of the DNA helix and
separation of the unwounded
portions of the two strands
STEP 02:

30. Then the polymerase
moves along the DNA
strand and, temporarily
a) First it causes hydrogen
bonds to form between the
ends of an RNA
nucleotides in the
nucleoplasm.
STEP 03

31. Then one at a time the RNA
polymerase breaks 2 of the 3
phosphate radicals away from each
of these RNA Nucleotides…………….
B)

32. When the RNA polymerase
reaches the end of the DNA gene
it encounters a new sequence of
DNA nucleotides called the chain
terminating
sequence…………………
c)

33. As the new RNA
strand is formed
its week hydrogen
breaks away thus
the RNA chain is
forced away from
the DNA and
released into
nucleoplasm.
d)

34. The code that is present in DNA strands
is transmitted in complementary form to
the RNA.
In short,

36. The ribose nucleotide bases always combine with
deoxyribose bases in the following combinations :
Combination of Bases:
DNA Base RNA Base
Guanine Cytosine
Cytosine Guanine
Adenine Uracil
Thymine Adenine

37. RNA:
• Ribonucleic acid, or RNA is one of the three major biological
macromolecules that are essential for all known forms of life (along
with DNA and proteins).
• DNA makes RNA, RNA makes Proteins.

38. Each type of RNA plays and independent and
entirely different role in protein formation.
There are four different types of RNA :
1- Messenger RNA
2- Ribosomal RNA
3- Transfer RNA
4- Micro RNA
Types of RNA :

39. Which carries the genetic code to the
cytoplasm for controlling the type of
protein formed.
Messenger
RNA:

40. Which transports activated amino
acids to the ribosomes to be used in
assembling the protein molecules.
Transfer RNA:

41. Which, along with about 75 different
proteins, forms ribosomes, the
physical and chemical structures on
which protein molecules are actually
assembled.
Ribosomal
RNA:

42. Micro RNA:
About 21 to 23 nucleotides that cannot be translated and
they regulate gene expression.

44. 44

45. TOPIC OUTLINE
 m-RNA
 Structure
 Function
 Codon
45

46. Biochemistry For Medics 46
Messenger RNA (m-RNA)
• Comprises only 5% of the RNA in the cell
• Most heterogeneous in size and base sequence
• All members of the class function as messengers
carrying the information in a gene to the protein
synthesizing machinery

47. mRNA STRUCTURE
AND FUNCTIONS

48.  The 5’ terminal end is capped by 7-
methyl guanosine triphosphate cap.
 The cap is involved in the recognition of
mRNA by the translating machinery
 It stabilizes m RNA by protecting it from
5’ exonuclease

49.  The 3’end of most m-RNAs have a polymer of
Adenylate residues( 20-250)
 The tail prevents the attack by 3’ exonucleases
 Histones and interferons do not contain poly A
tails
 On both 5’ and 3’ end there are non coding
sequences which are not translated (NCS)

50. 50

51. Structural Characteristics
of m-RNA
5’ cap and 3’ tail impart stability to m RNA by
protecting from specific exo nucleases.
51

52.  The m- RNA molecules are formed with the
help of DNA template during the process of
transcription.
 The sequence of nucleotides in m RNA is
complementary to the sequence of
nucleotides on template DNA.
 The sequence carried on m -RNA is read in the
form of codons.
 A codon is made up of 3 nucleotides
 The m-RNA is formed after processing of
heterogeneous nuclear RNA
52

54. What is rRNA:
In molecular biology, ribosomal ribonucleic acid (rRNA)
is the RNA component of the ribosome, and is essential
for protein synthesis in all living organisms. It constitutes
the predominant material within the ribosome, which is
approximately 60% rRNA and 40% protein by weight.
Ribosomes contain two major rRNA and 50 or
more proteins.
54

55. Structure:
The ribosomal RNAs form two subunits, the large
subunit (LSU) and small subunit (SSU). mRNA is
sandwiched between the small and large subunits.
 A ribosome also has three binding sites called A, P, and E.
 The A site in the ribosome binds to an aminoacyl-tRNA (a tRNA bound to
an amino acid).
 The amino (NH2) group of the aminoacyl-tRNA, which contains the new
amino acid, attacks the ester linkage of peptidyl-tRNA (contained within
the P site), which contains the last amino acid of the growing chain,
forming a new peptide bond. This reaction is catalyzed by peptidyl
transferees.
 The tRNA that was holding on the last amino acid is moved to the E site,
and what used to be the aminoacyl-tRNA is the peptidyl-tRNA.
55

56. 56

57. Formation of rRNA in
nucleolus:
 As the rRNA forms it collects in the nucleolus.
 In nucleolus it binds with ribosomal proteins to form
granular condensation products that are predominant
subunits of ribosomes
 Subunits release from nucleolus and transported through
nuclear pores to almost all parts of cytoplasm.
 In cytoplasm rRNA assembled to form mature, functional
ribosomes.
 Therefore, proteins are formed in the cytoplasm of cell not
in nucleolus as it doesn’t contain mature ribosomes.
 Size of nucleolus depends upon no. of rRNA present in it.
57

58. Synthesis of rRNA:
58

59. Location in cell:
The DNA genes for formation of rRNA are located in five
pairs of chromosomes in the nucleolus, each
chromosome contain many duplicates of these
particular genes because of large amount of rRNA
required for cellular functions.
59

60. Process of Translation:
 It is the whole process by which the base sequence of
an mRNA is used to order and to join the amino acids
into a protein.
60

61. Role of rRNA in translation:
 All types of RNA takes part in process of
translation.
 rRNA associate with a set of proteins to form
ribosomes.
 These complex structures, which physically move
along an mRNA molecule, catalyzed the assembly
of amino acids into protein chains.
 They also binds tRNAs and various accessory
molecules necessary for protein synthesis.
61

62. In protein synthesis:
62

65.  Small RNA molecule
 Clover leaf appearance
 Transfers amino acids to protein molecules
 Contains 80 nucleotides
 Each tRNA is specific for each amino acid
 Each tRNA recognizes specific codon on mRNA
 45 different types of tRNA are present in humans
Transfer RNA-The Anticodon:

66. Anticodon:
The specific code in the tRNA
that allows it to recognize a
specific codon is a triplet of
nucleotides bases and is called
an anticodon.
Anticodon bases
combine loosely by
hydrogen bonding
with the codon bases of
mRNA.

67.  Works as carrier of amino acids
 Participates in protein synthesis
(Translation)
Functions:

68. Also known as adenosine mono
phosphate AMP
CONSISTS of ribose, adenine, 1
phosphate
One end of tRNA is always
adenylic acid
A.A attaches at -OH group of
ribose in adinylic acid of tRNA
Adenylic acid:

71. A microRNA (abbreviated miRNA) is a small non-coding RNA
molecule (containing about 22 nucleotides) found in plants,
animals, and some viruses, which functions in RNA silencing
and post-transcriptional regulation of gene expression.

72. Discovery…
For the first time in Caenorhabditis elegans-a free
living nematode by Victor Ambros’ Laboratory in 1993.

73. Peculiarities…
 Encoded from transcribed DNA but not translated into
protein and hence called non-coding RNA.
 Regulate many functions of cells playing key role in:
> cell development, differentiation, death, proliferation,
apoptosis, neurodevelopment and indirectly in
Translation.
> siRNA(discussed later) may become useful therapeutic
tools to silence genes that contribute to the pathophysiology of
diseases.

75. Formation…

77. Functions… It performs RNA Silencing by introducing anti-
sense RNA molecules in mRNA.
 It regulates gene expression by controlling process
of Translation.
 it reduces efficiency of mRNA in protein synthesis.
 this is done by another type of miRNA-a silencing
RNA(siRNA) or short RNA 20-25 nucleotides.
 The siRNA are short double stranded RNA
molecules, 20-25 nucleotides in length.
 as siRNA enters cytoplasm, it activates RISC that
was generated along with miRNA.

78. References…
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regulates the proapoptotic gene hid in Drosophila. Cell 113: 25-36.
 Colin GA, Sevignani C, Dumitru CD, Hyslop T, Noch E, Yendamuri S, Shimizu M, Rattan S, Bullrich F, Negrini M, Croce CM (2004) Human miRNA genes are
frequently located at fragile sites and genomic regions involved in cancers. Proc. Natl. Acad. Sci. USA. 101: 2999-3004.
 Dostie J, Mourelatos Z, Yang M, Sharma A, Dreyfuss G. (2003) Numerous microRNPs in neuronal cells containing novel microRNAs. RNA 9(2): 180-6. Erratum
in: RNA 9(5): 631-2.
 Chen X. (2003) A MicroRNA as a Translational Repressor of APETALA2 in Arabidopsis Flower Development. Science E-Pub.
 Krichevsky AM, King KS, Donahue CP, Khrapko K, Kosik KS (2003) A miRNA array reveals extensive regulation of miRNAs during brain development. RNA 9:
1274-1281.
 Lee RC, Feinbaum RL, Ambros V (1993) The C. elegans heterochronic gene lin-4 encodes small RNAs with antisense complementarity to lin-14. Cell 75: 843-
854.
 Lim LP, Glasner ME, Yekta S, Burge CB, Bartel DP (2003b) Vertebrate microRNA genes. Science 299: 1540.
 Metzler M, Wilda M, Busch K, Viehmann S, Borkhardt A. (2004) High expression of precursor miRNA-155/BIC RNA in children with Burkitt lymphoma.
Genes Chromosomes Cancer 2: 167-169.
 Michael MZ, O’Connor SM, van Holst Pellekaan NG, Young GP, James RJ (2003) Reduced accumulation of specific microRNAs in colorectal neoplasia.
Molecular Cancer Research 1: 882-91.
 Pfeffer S, Zavolan M, Grasser FA, Chien M, Russo JJ, Ju J, John B, Enright AJ, Marks D, Sander C, Tuschl T. (2004) Identification of virus-encoded microRNAs.
Science 304(5671): 734-6.
 Reinhart BJ, Slack FA, Basson M, Pasquinelli AE, Bettinger JC, Rougvie AC, Horvitz HR, and G Ruvkun. (2000) The 21 nucleotide let-7 RNA regulates C.
elegans developmental timing. Nature 403: 901–906.
 Xu P, Vernooy SY, Guo M, Hay BA. (2003) The Drosophila microRNA Mir-14 suppresses cell death and is required for normal fat metabolism. Curr Biol 13(9):
790-5.
 Guyton and Hall Medical Physiology; ed 12 Genetic Control of Protein Synthesis, Cell Function, and Cell Reproduction_Unit-1_ The process of Transcription.