Genome organisation

Genome Organisation of Prokaryotes and Eukaryotes

1. The Genome Organization of
Prokaryotes and Eukaryotes

2. Genomes
The word “genome,” coined by German botanist Hans Winkler in
1920, was derived simply by combining gene and the final
syllable of chromosome.
The genome includes both the genes and non-coding sequences of
DNA.
An organism’s genome is defined as the entire collection of
genes and all other functional and non-functional DNA sequence
in a haploid set of chromosomes.
It includes structural genes, regulatory genes and non-functional
nucleotide sequence.
The genome is the ultimate source of information about an
organism.

3. "Genes" are units of genetic information present on
the DNA in the chromosomes and chromatin.
"Genome" is the entirety of an organism’s hereditary
organization. It is encoded either in DNA, or for
many types of viruses, in RNA.

4. Continue…
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.

5. Prokaryotes and Eukaryotes genome
Prokaryotes Eukaryotes
Single cell Single or multi cell
No nucleus Nucleus
One piece of circular DNAChromosomes
No mRNA post transcriptional
modification
Exons/Introns splicing

6. Prokaryotic and Eukaryotic Cells
Chromosomal differences
Prokaryotes
The genome of E.coli contains amount of
4X10
6
base pairs
> 90% of DNA encode protein
Lacks a membrane-bound nucleus.
Circular DNA and supercoiled domain
Histones not present

7. oProkaryotic genomes generally contain one
large circular piece of DNA referred to as a
"chromosome" (not a true chromosome in
the eukaryotic sense).
oSome bacteria have linear "chromosomes".
oMany bacteria have small circular DNA
structures called plasmids which can be
swapped between neighbors and across
bacterial species.
Continue…

8. oThe term plasmid was first introduced by the
American molecular biologist Joshua
Lederberg in 1952.
oA plasmid is separate from, and can
replicate independently of, the chromosomal
DNA.
oPlasmid size varies from 1 to over 1,000
(kbp).
Plasmid

9. Eukaryotes
The genome of yeast cells contains
1.35x10
7
base pairs
A small fraction of the total DNA encodes
protein.
•Many repeats of non-coding sequences
All chromosomes are contained in a membrane
bound nucleus
•DNA is divided between two or more
chromosomes
A set of five histones
•DNA packaging and gene expression
regulation

10. Prokaryotic and Eukaryotic Chromosomes

11. Eukaryotic Genome
Nuclear
Mitochondrial
Plasmids (in yeast)
Chloroplasts (in Plants)

12. Human Genome-General Information
Genetic material in humans is stored
in two organelles: nucleus (about
3200 Mbp) and mitochondria (16.6
kb).
Human chromosomes are not of
equal sizes; the smallest,
chromosome 21, and the largest,
chromosome 1.
 Only a very small amount of human
DNA is responsible for the
differences among humans, indeed
among all organisms.

13. Number of genes in the human
genome
Number of genes at least 100,000.
However, the number of protein encoding genes is only
‐
~20,000 to 25,000.

15. Mitochondrial DNA
Mitochondrial DNA is a DNA located in Mitochondria, that convert
chemical energy from food into the form that cells can use, ATP.
Each mitochondrion is estimated to contain 2-10 mt DNA and there
are many mitochondria in each of the cells.
Mitochondrial DNA is similar to prokaryotic DNA. There are no
histones or any other protein associated with mitochondrial DNA.
The genes contain no introns. Maternal inheritance.
The genes in mitochondrial DNA code for mitochondrial ribosomes
and transfer RNAs.
Some genes code for polypeptide subunits of the electron transport
chain common to all mitochondria.

17. Nuclear DNA
Nuclear DNA is a DNA contained within the nucleus of the
Eukaryotic organisms .
Nuclear DNA is Double-stranded and linear.
Nuclear DNA is made up of 3.3 billion DNA base pairs and only two
copies of nuclear genome per somatic cells.
Nuclear genome has 20,000-25,000 genes including mitochondrial
genes.
Nuclear genes codes for all proteins required for its function.
Nuclear genome has introns or non-coding DNA and accounts for
93% of total DNA.
The nuclear genome is inherited equally from both parents.

18. Nuclear Genome
3.2 Gb
Genes and gene related DNAExtragenic DNA
Coding and Regulatory DNANon-Coding DNA
Pseudogenes Gene Fragments Introns, etc..

19. Mitochondrial DNA Vs Nuclear DNA

20. Chloroplasts DNA
Chloroplasts DNAs are circular, double-stranded DNA molecule
located in Stroma of chloroplasts.
The chloroplast DNA are typically 120,000-170,000 base pairs long.
There is more than one copy of genome in each chloroplast.
Chloroplast DNA is not associated with true histone, but a histone-
like chloroplast protein (HC) coded by the chloroplast DNA that
tightly packs chloroplast DNA ring into a nucleoid.
Chloroplasts genomes typically contain 100-200 genes and encode
proteins essential for photosynthesis.
Post-transcriptional RNA processing plays an important role in
chloroplast gene expression.
The chloroplast can also influence the expression of nuclear genes.

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