WELFREDO LUBRICO YU,JR. BSEd -BIO.SCI. 3 COLLEGE OF TEACHER EDUCATION SDSSU,Tandag CITY

1. MICROBIAL
GENETICS
PREPARED BY
WELFREDO YU,JR.

2. STRUCTURE AND FUNCTION
OF GENETIC MATERIAL
DNA & RNA
DNA=deoxyribonucleic acid
RNA=ribonucleic acid
Basic building blocks:
Nucleotides
Phosphate group
Pentose sugar
Nitrogenous base

3. STRUCTURE OF DNA
Double stranded (double helix)
Chains of nucleotides
5’ to 3’ (strands are anti-parallel)
Complimentary base pairing
• A-T
• G-C

4. DNA STRUCTURE
Phosphate-P
Sugar-blue
Bases-ATGC

5. DNA REPLICATION
Bacteria have closed, circular DNA
Genome: genetic material in an organism
E. coli
• 4 million base pairs
• 1 mm long (over 1000 times larger that actual bacterial cell)
• DNA takes up around 10% of cell volume

6. DNA REPLICATION-OCCURS AT
THE REPLICATION FORK
5’ to 3 ‘
DNA helicase-unzips + parental DNA strand
that is used as a template
• Leading stand (5’ to 3’-continuous)
*DNA polymerase-joins growing DNA strand after
nucleotides are aligned (complimentary)
• Lagging strand (5’ to 3’-not continuous)
*RNA polymerase (makes short RNA primer)
*DNA polymerase (extends RNA primer then digests RNA
primer and replaces it with DNA)
*DNA ligase (seals Okazaki fragments-the newly formed
DNA fragments)

7. REPLICATION FORK

8. PROTEIN SYNTHESIS
DNA------- mRNA------ protein
transcription translation
Central Dogma
of Molecular Genetics

9. TRANSCRIPTION
One strand of DNA used as a template to
make a complimentary strand of mRNA
Promoter/RNA polymerase/termination
site/5’ to 3’
Ways in which RNA & DNA differ:
• RNA is ss
• RNA sugar is ribose
• Base pairing-A-U

10. TRANSCRIPTION

11. TYPES OF RNA
Three types:
• mRNA: messenger RNA
• Contains 3 bases ( codon)
• rRNA: ribosomal RNA
• Comprises the 70 S ribosome
• tRNA: transfer RNA
• Transfers amino acids to ribosomes for protein
synthesis
• Contains the anticodon (3 base sequence that is
complimentary to codon on mRNA)

12. GENETIC CODE
DNA: triplet code
mRNA: codon (complimentary to triplet code of DNA)
tRNA: anticodon (complimentary to codon)

13. GENETIC CODE
Codons: code for the production of a specific amino acid
20 amino acids
3 base code
Degenerative: more than 1 codon codes for an amino acid
Universal: in all living organisms

14. GENETIC CODE

15. TRANSLATION
Three parts:
• Initiation-start codon (AUG)
• Elongation-ribosome moves along mRNA
• Termination: stop codon reached/polypeptide
released and new protein forms
rRNA=subunits that form the 70 S
ribosomes (protein synthesis occurs here)
tRNA=transfers amino acids to ribosomes
for protein synthesis)

20. MUTATIONS
Changes in base sequence of DNA/lethal and inheritable
Can be:
• Harmful
• Lethal
• Helpful
• Silent

21. NORMAL DNA/MISSENSE
MUTATION

22. NONSENSE
MUTATION/FRAMESHIFT
MUTATION

23. GENETIC TRANSFER
IN BACTERIA
Genetic transfer-results in genetic variation
Genetic variation-needed for evolution
Three ways:
• Transformation: genes transferred from one
bacterium to another as “naked” DNA
• Conjugation: plasmids transferred 1 bacteria to
another via a pilus
• Transduction: DNA transferred from 1 bacteria to
another by a virus

24. TRANSDUCTION BY A
BACTERIOPHAGE

25. TRANSFORMATION

26. CONJUGATION IN E.
COLI

27. CONJUGATION
CONTINUED…

28. CONJUGATION
CONTINUED…