This document provides an overview of split genes and ribozymes. It discusses how split genes have interrupted sequences called introns between exons, and how this was discovered in 1977. It also defines ribozymes as RNA molecules with catalytic activity, describes several natural ribozymes including group I and II introns and hammerhead ribozymes. Applications of engineered ribozymes in gene therapy and inhibiting gene expression are also mentioned.

1. Topic :
SPLIT GENES AND CONCEPT OF RIBOZYME
Assignment : Molecular Biology
Submitted To : Dr. Fouzia Tanvir
Submitted By : Ali Rizwan
Roll No : 1033
Class : Bs Zoology Morning
Submitted Date : 07-01-2024

2. Table of Contents
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Split Genes
History
Types of Sequences
Significance of split genes
Introduction of ribozyme
History
Catalytic Actiivity
Types of Riboymea
Group l intron splicing
Group ll intron splicing
RNase P
HammerHead Ribozyme
Spliceosome
Hairpin Ribozyme
Application of Ribozymes
References

3. Split Genes
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Genes with interrupted sequence of nucleotides are
referred to as split genes.
Usually a gene has a continuous sequence of
nucleotides.
In other words, there is no interruption in the
nucleotides sequence of a gene.such nucleotide
sequence codes for a particular single polypeptide
chain.

5. History
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However, it was were observed that the sequence of
nucleotides was not contains in case of some genes,the
sequences of nucleotides were interrupted by intervening
sequences.
Split genes were independently discovered by Richard J.
Roberts and Philip A. Sharp in 1977,for which they
shared the 1993 Nobel prize in Physiology or Medicine.
The first observations of interrupted genes, i.e, genes in
which there are noncoding intron sequences between the
coding exon sequences ,were made in animal viruses in
1977.

6. Types of Sequences
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Split Genes have two types of sequences:
Normal sequences. ( exons)
Interrupted sequence ( introns)
1) Normal sequence:
This represents the sequence of nucleotides
which are included in the mRNA is translated
from DNA of split gene.these sequences code
for a particular polypeptides chain and are
known as exons.

7. The intervening or interrupted sequences of split gene are
known as introns. These sequences do not code for any
peptide chain. Moreover, interrupted sequences are not
included into mRNA which is transcribed from DNA of split
genes.
2) Interrupted sequence ( introns) :

8. Significance of Split Genes
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The significance of split organisation of eukaryotic genes
is not clear.
In some cases, different exons of a gene code for
different active regions of the protein molecule e.g.in the
case of antibodies. Thus, it has been suggested that
introns are relics of evolutionary processes that brought
together different ancestral genes to form new larger
genes. It is also possible that some introns have been
introduced within certain exons during evolution.

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Ribozyme technology deals with the
use of ribozymes for different purposes
including therapeutic and research
purposes.
RNA are the molecule which show
catalytic activity.

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The first ribozyme was discovered in 1980.
Reseachers demonstrating that RNA function
both as a genetic material or as a biological
catalyst.
This contribute to the worldwide hypothesis
that RNA may played a crucial role in the
evolution of self-replicating systems.
This reffered as RNA World Hypothesis.

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A ribozyme (ribonucleic acid enzyme) is an
RNA molecule that is capable of performing
specific biochemical reactions, similar to
the action of protein enzymes.
Ribozyme means ribonucleic acid enzyme.
It also called an RNA enzyme or catalytic
RNA
It contains an active site that consists
entirely of RNA

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Ribozymes are RNA molecules endowed with catalytic
activity and capable of cleaving mRNA molecules in a
sequence specific, catalytic manner.
They contain sequences for selective ligation with target
mRNAs which confers upon them high specificity.
They also contain sequences that perform cleavage
reactions with the target mRNA.
By modifying the substrate recognizing sequences,
ribozymes can be specifically tailored for the
suppression of particular genes.

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Natural ribozymes can be classified into
two
different groups:
1) the self-cleaving RNAs which include
the hammerhead, hairpin, hepatitis delta
virus, Varkud ,satellite .
2) the self-splicing ribozymes that are
the group I and II introns, RNase P.

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Group I intron ribozymes constitute one of
the main classes of ribozymes.
Found in bacteria, lower eukaryotes and
higher plants.
Group I introns are also found inserted into
genes of a wide variety of bacteriophages of
Gram-positive bacteria.
However, their distribution in the phage of
Gram- negative bacteria is mainly limited
to the T4, T-even and T7-like like
bacteriophages.

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Group II introns have been found in bacteria and
in the mitochondrial and chloroplast genomes of
fungi, plants, protists, and an annelid worm.
Mechanism:
The 2’OH of a specific adenosine acts as a
nucleophile and attacks the 5’ splice site creating a
branched intron structure. The 3’ OH of the 5’ exon
attacks the 3’ splice site,
ligating the exons and releasing the intron as a lariat
structure.

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Ribonuclease P (RNaseP), a
ribonucleoprotein, is an essential tRNA
processing enzyme found in all living
organisms.
Since its discovery almost 40 years ago,
research on RNase P has led to the
discovery of the catalytic properties of
RNA, and of the only known, naturally
occurring RNA enzymes.

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Hammerhead ribozymes (HHRZs) are tiny
autocatalytic RNAs that cleave single-stranded
RNA.
They are found in nature as a part of certain
virus- like elements called virusoids, which use
a "rolling- circle replication" mechanism to
reproduce their small, circular RNA genomes.
The HHRZ is so named because its secondary
structure is similarly to that of a hammer head,
but actually its tertiary structure is more like ‘Y’
shaped.

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Spliceosome is a large and complex
molecular machine.
Which is found in the nucleus of
eukaryotic cells.
The spliceosome removes introns
from a transcribed pre – mRNA.
This process known as SPLICING.

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motif that catalyzes RNA
processing reactions essential for
replication of the satellite RNA
molecules in which it is
embedded.
These reactions are
selfprocessing,
i.e. a molecule rearranging its own
structure. Both cleavage and end
joining reactions are mediated by
the ribozyme motif.

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Ribozymes are capable of specially
cleaving RNA molecules.
Ribozymes are used for to inhibit gene
expression.
Phase 1 trials using ribozyme gene
therapy. Synthetic ribozyme directed
against HIV RNA called gene shears.

24. References
Fundamentals of Biochemistry,
By :- Dr. J.l. Jain
Dr. Sunjay Jain
Nitin jain
Genetics
By: P. K. Gupta
WWW. Google.com
https://www.genescript.com>secondary gene...
Www.slidesshare .com