This document discusses bacterial genetics. It begins by explaining that bacterial properties are controlled by genes in their chromosomal DNA, which is replicated to maintain traits across generations. While bacteria have no nucleus or nucleolus, their DNA forms the classic double helix structure described by Watson and Crick. Genetic information is stored in codons that code for amino acids. Bacteria can experience phenotypic variation from environment or genotypic variation through mutation or gene transfer via transformation, transduction, conjugation, or cell fusion. Mutation may occur spontaneously or be induced, and can involve changes like base substitutions or frameshifts. Gene transfer allows uptake of external DNA and transmission of genes between bacteria.

1. BACTERIAL GENETICS

2. INTRODUCTION
 All properties of bacteria-
structure, morphology,
metabolism, multiplication
and hereditary characters are
encoded in and controlled by
genes present in
chromosomal DNA
 Bacteria like other organisms
breed true and their
characters are constant from
generation to generation
 Accomplished by replication
of bacterial chromosomal
DNA

3. BACTERIAL NUCLEUS
 Not seen by routine stains
 Demonstrated by acid/ ribonuclease hydrolysis stained
with fulgens stain
 Seen by electron microscopy
 Length- 1mm
 No nucleolus, nuclear membrane
 Haploid
 Replication- simple fission

4. BACTERIAL DNA
 Watson and crick model- 2
strands of nucleotides wound
together to form a double
helix
 Purines- adenine (A), guanine
(G)
 Pyrimidines- cytosine (c),
thiamine (t)
 A binds with T and C with G
 Binds with hydrogen bonds

5. RNA………….
 Structurally similar to DNA
except
 Contains RIBOSE sugar
 Contains base “uracil”
 Three types of RNA
I. M- RNA
II. T-RNA
III. R-RNA

6.  Genetic information is stored as code
 Code consist of three bases called as CODON
 Each codon codes for 1 amino acid
 Total 64 codons present of which 61 code for 20 amino acids
 3 codons – UAA, UAG, UGA are nonsense codon terminate protein
synthesis

7.  Segment of DNA coding a single polypeptide is called a gene
 DNA has many genes
 Large no of genes are present in chromosome
 In higher forms of life stretches of DNA do not function as codons-
INTRONS
 Stretches with coded genes- EXONS

8.  Length of DNA expressed as kilo bases
 1kb- 1000 base pairs
 Bacterial dna- 4000 kb
 Human genome- 3 million kb

9. FUNCTIONS
 Synthesis of protein which finally are expressed as
morphology and biological particulars of bacterium-
metabolism, pathogenicity, enzymes
 Genotype- genetic potential of cell
 Phenotype- physical expression of genotype

10. Bacterial variation
 Phenotypic variation
 Genotypic variation a) mutation
b) gene transfer
i)transformation
ii)transduction
iii) conjugation
iv) cell to cell fusion

11. Phenotypic variation
 Morphological,
biochemical, and
metabolic characters
shown by particular
bacterium
 Non heritable
 Reversible
 Depends on
environment
 Eg- pleomorphism,
beta galctosidase in
e.coli
Genotypic variation
 Collection of genes
encoding characters is
called genotype
 Heritable
 Irreversible
 Involves changes in
genetic material

12. MUTATION
 “Random undirected
heritable variation due to any
change in nucleotide
sequence of a gene which
may or may not be physically
expressed”
 Mutation can involve any
gene of bacterial
chromosome.
 Form of gene when first
isolated from nature- wild
type allele of gene
 Arising out of mutation-
mutant allele

13. Molecular basis
 Triplet code is altered, due to change in nucleotide
sequence
 Therefore a new amino acid is produced
 This change is transferred during transcription and
translation process
 Most mutations are undetected

14. TYPES OF MUTATION
 POINT MUTATION : change in nucleotide sequence
A) Base pair substitution :
i) TRANSITION : AT replaced by CG
purine replaced by purine or pyrimidine by
pyrimidine

15. ii) TRANSVESION : purine replaced with pyrimidine and vice versa
AT- CG becomes AC-TG
2) FRAME SHIFT MUTATION : one or few adjacent base pair are inserted
or deleted from DNA. This shifts the normal reading frame of coded
message to new set of triplet codons.

17.  MULTISITE MUTATION:
alteration involving large no of base pairs, 4 types
1)Loss
2)Gain
3)Duplication
4)Inversions
 SPONTANEOUS : occur in the presence of known
mutagen
 INDUCED : physical / chemical agent induce
mutation

18. Physical agents
 U.v light
 Ionising radiations
 Visible light
 heat
Chemical agents
 Directly acting
o Anti cancer drugs
o Alkylating agents
o Nitroso compounds
o Nitropurines
 Acting indirectly
o Benzpyrine
o Alfa toxin

19. EFFECTS OF MUTATION
 Non sense : partial polypeptide is formed
 Mis sense mutation : produces different a.a
 Suppression mutation : second mutation
restores the function of the gene

20. LAB OBSERVATION OF
MUTATION
A) GENE SEQUENCING
B) STUDY OF OBSERVABLE PHENOTYPE CHANGE. LOSS
OR GAIN OF SPECIFIC ENZYME

21. DEMO OF DRUG RESISTANT
MUTANT
 Fluctuation analysis method : not precise
 Replica plating method :
i)bacterial colonies are grown on normal media
ii) charge the cylindrical block with sterile velvet press it
on the plate containing the colonies and then press it
on agar with drug
iii) colonies growing on the plate with drug are mutants

23. TRANSFORMATION
 Direct uptake and absorption of exogenous bacterial
DNA by recipient cell
 GRIFFITH EXPERIMENT
 Non capsulted rough strain- no effect
 Capsulated smooth strain heat killed- no effect
 Mixture of strain- kills the mice, and smooth strain is
recovered from mice.

25.  Fragment of DNA determining capsule formation was transferred
from smooth strain to rough strain, which became virulent
 Transformation occurs in species of bacillus, neisseria, H.influenzae
etc
 Can occur naturally or forced by t/t with high salt and temp. shock
 Occurs in realted spp except for-pseudomonas and pneumococci

26. TRANSDUCTION
 Transmission of a piece of DNA/ plasmid/ episomes
from one bacterial cell to another by bacteriophage
 A number of B phages can transduce bacterial DNA.
 It is seen in escherichia, salmonella, shigella, kleibseilla,
proteus, pseudomonas, bacillus and streptococci
 Bacteriophages are viruses that grow in bacterial cells

27. Types of transduction
 Generalised : any segment of donar DNA at random
 Restricted : only a particular segment ( genetic trait)
transduced. E.g lamda phage
 Penicillin resistance in staphylococci due to plasmids
 Uses
 Treatment of inborn errors of metabolism
 Genetic engineering

29. LYSOGENIC CONVERSION
 TEMPERATE CYCLE :
 Phage DNA intergrated- new genetic element
Multiplies synchronously with bacterial DNA
 Transferred to daughter cells- net generation
 Imparts new characters to host cells.
 Lysogenic convesion/ lysogenic bacteria
 E.g : diptheria bacilli can produce toxin when beta
phage is present

31. CONJUGATION
 Transfer of genetic material from one bacterium to
another bacterial cell, by cell to cell contact
 Only bacteria possessing F plasmid can act as donars,
while cells lacking F act as recpient.
 Capacity to donate genetic material depends o fertility
factor in the cell. This F factor has been identified as
conjugate plasmid, determining the formation of sex
pilus