This document discusses gene organization in microbes. It begins by defining the term "genome" and explaining that a genome contains an organism's complete set of DNA. Prokaryotes like bacteria have simpler genomes than eukaryotes, with a single circular chromosome and sometimes additional plasmids. Plasmids are small circular DNA structures that can be transferred between bacteria. The document then compares prokaryotic and eukaryotic chromosomes, noting that eukaryotes have membrane-bound nuclei while prokaryotes do not. It also discusses viral genomes, karyotypes, and different hypotheses about the relationship between genes and proteins.

1. BABA SAHEB BHIM RAO AMBEDKAR
UNIVERSITY
GENE ORGANISATION IN MICROBE
BY :- PRASHANT TRIPATHI
M.SC[INDUSTRIAL MICROBIOLOGY]
BBAU

2. GENE ORGANISATION
• The word “genome,” coined by German botanist
Hans Winkler in 1920, was derived simply by
combining gene and the final syllable of
chromosome.
• An organism’s genome is defined as the complete
haploid genetic complement of a typical cell.
• In diploid organisms, sequence variations exist
between the two copies of each chromosome
present in a cell.
• The genome is the ultimate source of information

3. IN CONTINUATION :-
• The number of genomes sequenced in their entirety
is now in the thousands and includes organisms
ranging from bacteria to mammals.
• The first complete genome to be sequenced was that
of the bacterium Haemophilus influenzae, in 1995.
• The first eukaryotic genome sequence, that of the
yeast Saccharomyces cerevisiae, followed in 1996.
• The genome sequence for the bacterium Escherichia
coli became available in 1997 .
• The much larger effort directed at the human genome
was also accelerating.

4. PROKARYOTES AND EUKARYOTES
GENOME
Prokaryotes Eukaryotes
Single cell Single or multi cell
No nucleus Nucleus
One piece of circular DNA Chromosomes
No mRNA post transcriptional
modification
Exons/Introns splicing

5. CHROMOSOME DIFFERENCE
[PROKARYOTIC AND EUKARYOTIC CELL]
 PROKARYOTIC CELL
 Lacks a membrane bound nucleus.
 Circular DNA and supercoiled domain.
 Histones not present.
 Prokaryotic genomes generally contains one large circular
piece of DNA refered to as a CHROMOSOME.
 Some bacteria have linear chromosome.
 Many bacteria have small circular DNA str. Called PLASMIDS
which can be swapped between neighbours and across
bacterial species.

6. PLASMID
o The term plasmid was first
introduced by the American
molecular biologist Joshua
Lederberg in 1952.
o A plasmid is separate form,
and can replicate
independently of, the
chromosomal DNA.
o Plasmid size varies from 1 to
over 1,000 (kbp).

7. Classification and types of
PLASMID
• Plasmids can be broadly classified into
conjugative plasmids and non-conjugative
plasmids.
•In the complex process of conjugation, plasmid
may be transferred from one bacterium to
another via sex pili encoded by some of
the tra genes.
• Non-conjugative plasmids are incapable of
initiating conjugation, hence they can be
transferred only with the assistance of conjugative
plasmids.

8. Another way to classify plasmids is by
function. There are five main classes:
• Fertility F-plasmids, which contain tra genes. They are capable
of conjugation and result in the expression of sex pili.
• Resistance (R) plasmids, which contain genes that provide
resistance against antibiotics or poisons.
• Col plasmids, which contain genes that code
for bacteriocins, proteins that can kill other bacteria.
• Degradative plasmids, which enable the digestion of unusual
substances, e.g. toluene and salicylic acid.
• Virulence plasmids, which turn the bacterium into a pathogen.

9. VIRAL GENOME
A virus has either a DNA or an
RNA genome and is called a DNA virus or an
RNA virus, respectively. The vast majority
of viruses have RNA genomes. Plant
viruses tend to have single-stranded
RNA genomes and bacteriophages tend to
have double-stranded DNA genomes.

10. IN EUKARYOTES :-
 The genome of different
eukaroytic cells contains
different base pairs.
 A small fraction of the total
DNA encodes protein.
• Many repeats of coding &
non-coding sequences.
 All chromosomes are
contained in a membrane
bound nucleus.
 Histone protein is present.

13. KARYOTYPE
o The study of chromosomes, their structure and
their inheritance is known as Cytogenetics.
o Each species has a characteristic number of
chromosomes and this is known as karyotype.

16. GENES – GENETIC INFORMATION
• One gene : one enzyme
hypothesis: summarizes
that a gene is a stretch of
DNA coding for one or
more isoforms of a single
enzyme.
• One gene : one
polypeptide hypothesis: a
gene is responsible for the
production of a single
polypeptide.
• Many genes: one protein:
• e.g. Hemoglobin requires
different globin genes.

17. THANK YOU