A detail comparison between the genomic organization between prokaryotic genome and eukaryotic genome.

1. Bacterial Genomic Organization

2. Bacterial Genomic Organization
Presented by Negash Alamin (BSC)
Medical labscientist
Feb,22,2019

3. Introduction
• Prokaryotic genomes are somewhat different in
organization but not in function from eukaryotic
cells.
• Most of their genetic material of bacteria is located
in the nucleoid and some genetic material might be
present as plasmid in the cytoplasm.

4. Introduction cont'...
• The nuceoid is an irregularly shaped region within
the cell.
• The genome of bacteria is generally circular and
double stranded piece of DNA. The size of the DNA
is measured in bits just like binary computer data
calculations and varies in length from bacteria to
bacteria.

5. Introduction cont'...
• The nucleoid consists of DNA, RNA and nucleoid
proteins which are associated with the supercoiled
structure of the DNA; which are distinct from
histones in eukaryotic cells.
•

6. Further Details on Prokaryotic cell
organization
• The circular structure of DNA in bacteria replicates
differently from the eukaryotic cells.
• There is a supercoiling which makes the packaging of
data in the tiny cell easier; this coiling puts a strain on
the DNA itself.
• This coiling of DNA can cause disruption to
transcription and even to cell death. The double helix
twists around its axis approximately every 10 bases.

7. Details....cont'
• The DNA is a molecule composed of nucleotides
guanine and adenine (purines) and cytosine and
thymine (pyramidines). In addition, there are
deoxyribose sugars and phosphate groups.
•

8. Details...Continued
• In general, there are two terms to remember one
is twist: which is the number of turns the ladder of
DNA rotates on itself.
• writhe: the number of times the DNA crosses over
on itself (supercoils) like a circle for example
crossing over to give the figure number eight.

9. The DNA twisting Positions
• It can twist or writhe to the left or to the right

10. Types of twists & writhe fig.1

11. Twists & writhe continued....

12. Twists & writhe continued

13. The Nuceloid Inside Prokaryotic
bacteria

14. More illustrations to compare &
contrast genomic organization

15. Organization in Eukaryotes cont'...

16. More illustrations cont'....

17. Important points to Remember
1-Positive supercoils: loosening the DNA strand
2-Negative supercoils: tightening the DNA strand
3-Codons: a set of rules by which information
encoded within a gene is translated.
4-Open reading frames (ORF): is a part of the DNA that
contains no stop codons. It is the protein coding region
of the helix.

18. Important points.....
5-Semiconservative replication: A type of replication
where the daughter strand is made of one parental
strand and one new daughter strand.
6- Nucleotide: The important four molecules ATGC
without the sugar backbone.
7- Base: nucleotide plus the sugar back bone.
8- Replication fork: The point where the DNA is separated
into single strands, and where new DNA will be
synthesized.

19. DNA replication steps
1-Initiation: finding origin site in the nucleoid, slicing
the strand and adding primers.
2- Elongation: Dna polymerase III along with other
enzymes drives transcription.
3-Termination: The replication process senses a stop
codon and ends the replication process.

20. Materials Needed for Replication
1- DNA template
2.dNTPs:dATP,dTTP,dGTP,dCTP (deoxyribonucleoside
5’-triphosphates)
3. DNA polymerase III and I
4. RNA primer

21. Materials needed cont'...
5-DnaB protein: also called Helicase (it unwinds DNA)
6-DnaA protein: recognizes the origin of replication in
the circular bacteria genophore; where the Origin site
is a A/T rich site 245 base pairs long where replication
is initiated.
8- DNA gyrase: relives strain on the DNA strand and
supercoiling.

22. Materials needed cont'...
9- Primase (DnaG protein): synthesizes RNA primers.
10-DnaC: Binds DnaB (helicase) at origin site.
11- Dna ligase: connects Okazaki fragments.

23. The Replication Process

25. Conclusions
Even though prokaryotic bacteria are the first to
evolve in evolutionary history; their mechanism of
storing the DNA is not that different from the
advanced and specialized cells called eukaryotes.

26. Conclusions cont'...
In this short note we have tried to elaborate the
mechanisms of genomic organization (how DNA is
stored in primitive cells i.e. bacteria) and also we
have added how the replication process moves
ahead so that the reader gets a full picture of the
process.

27. www.kahnacademy.com
www.lumenlearning.com
www.asm.org
NIH Human Microbiome project
www.hmpdacc.org
Lecture notes from 2nd yr 3rd semester: Molecular
biology
References

28. End of Presentation
Questions?