DNA is a double helix structure located in the nucleus that carries genetic information and consists of nucleotides, which include bases adenine, thymine, cytosine, and guanine. Gene expression involves the activation of genes to produce proteins, with processes differing between prokaryotes and eukaryotes, and is characterized by transcription and translation events. Eukaryotic DNA contains coding (exons) and noncoding (introns) regions, while prokaryotic processes occur in the cytoplasm.

1. DNA and Gene
DNA and Gene
Expression
Expression

2. DNA
DNA
 Deoxyribonucleic Acid
Deoxyribonucleic Acid
 Double helix
Double helix
 Carries genetic information
Carries genetic information
 Located in the nucleus
Located in the nucleus
 The monomer is a
The monomer is a
nucleotide
nucleotide
– A phosphate
A phosphate
– A ribose sugar
A ribose sugar
– A nitrogenous base
A nitrogenous base

3. What are the bases in DNA
What are the bases in DNA
 A – adenine
A – adenine
 T – thymine
T – thymine
 C – cytosine
C – cytosine
 G – guanine
G – guanine
 Base pair rules
Base pair rules

4. Where is DNA located in the Cell?
Where is DNA located in the Cell?

5. Where are the genes located?
Where are the genes located?
 Genes are located on
Genes are located on
the chromosomes.
the chromosomes.
 Every species has a
Every species has a
different number of
different number of
chromosomes.
chromosomes.
 There are two types
There are two types
of chromosomes:
of chromosomes:
autosomes and sex
autosomes and sex
chromosomes
chromosomes

6.  Genes are located on the chromosomes
Genes are located on the chromosomes
which are found in the nucleus of a cell.
which are found in the nucleus of a cell.
 When a cell is undergoing cell
When a cell is undergoing cell
reproduction, the chromosomes are
reproduction, the chromosomes are
visible. Chromosomes appear when the
visible. Chromosomes appear when the
chromatin condenses and become visible.
chromatin condenses and become visible.
 Most of the time (90%) the genetic
Most of the time (90%) the genetic
material in the form of chromatin.
material in the form of chromatin.
 A genome is the complete genetic
A genome is the complete genetic
information contained in an individual.
information contained in an individual.
– (gene + chromosome)
(gene + chromosome)

7. What is gene expression?
What is gene expression?
Gene expression is the
Gene expression is the
activation of a gene
activation of a gene
that results in a
that results in a
protein.
protein.

8. Gene expression takes place
Gene expression takes place
differently in prokaryotes and
differently in prokaryotes and
eukaryotes.
eukaryotes. What is a
What is a
prokaryotes? Eukaryotes?
prokaryotes? Eukaryotes?
 Prokaryotes
Prokaryotes
– No membrane bound
No membrane bound
organelles (nucleus)
organelles (nucleus)
– More primitive
More primitive
organisms
organisms
– Only one circular
Only one circular
chromosome
chromosome
– Bacteria are the only
Bacteria are the only
organisms that are
organisms that are
prokaryotes.
prokaryotes.
 Eukaryotes
Eukaryotes
– Membrane bound
Membrane bound
organelles ( specialize in
organelles ( specialize in
function –nucleus,
function –nucleus,
mitochondria,
mitochondria,
chloroplast)
chloroplast)
– Chromosomes are in
Chromosomes are in
pairs and not circular
pairs and not circular
– All organisms that are
All organisms that are
not bacteria: protist,
not bacteria: protist,
fungi, plants and animals
fungi, plants and animals

9.  In Eukaryotes, following mitosis or meiosis,
In Eukaryotes, following mitosis or meiosis,
DNA recoils but certain regions remain
DNA recoils but certain regions remain
relaxed for transcription. The areas of
relaxed for transcription. The areas of
relaxed DNA are called
relaxed DNA are called euchromatin
euchromatin.
.
 Transcription is the
Transcription is the
Reading of the DNA and
Reading of the DNA and
Changing the code to
Changing the code to
mRNA.
mRNA.
 Translation is changing
Translation is changing
The mRNA into a trait by
The mRNA into a trait by
Using tRNA to interpret the
Using tRNA to interpret the
mRNA.
mRNA.

10.  DNA in eukaryotes has regions of coding and
DNA in eukaryotes has regions of coding and
noncoding DNA. The regions of DNA that
noncoding DNA. The regions of DNA that
code for proteins or traits are called
code for proteins or traits are called EXONS
EXONS,
,
while the regions that do not code for
while the regions that do not code for
proteins are called
proteins are called INTRONS.
INTRONS.
cytoplasm
cytoplasm

11.  In prokayotes, transcription and
In prokayotes, transcription and
translation occur in the cytoplasm.
translation occur in the cytoplasm.
 In eukaryotes, transcription occurs
In eukaryotes, transcription occurs
inside the nucleus in a two step
inside the nucleus in a two step
sequence of events.
sequence of events.
– Pre-mRNA includes both introns and exons
Pre-mRNA includes both introns and exons
for the gene.
for the gene.
– mRNA is only the coding portion (exons).
mRNA is only the coding portion (exons).
 Translation occurs in the cytoplasm at
Translation occurs in the cytoplasm at
the ribosomes.
the ribosomes.
– Reminder: The are three (3) types of RNA
Reminder: The are three (3) types of RNA
 Messenager (mRNA)
Messenager (mRNA)
 Transfer (tRNA)
Transfer (tRNA)
 Ribsomal (rRNA)
Ribsomal (rRNA)

12. Translation
Translation
 RNA
RNA
– Single stranded
Single stranded
– Does not contain thymine
Does not contain thymine
but has uracil instead.
but has uracil instead.
 tRNA carries 3 base pair
tRNA carries 3 base pair
code for specific amino
code for specific amino
acid.
acid.
 Amino acids compose
Amino acids compose
polypeptid chains.
polypeptid chains.
 One or more polypeptide
One or more polypeptide
chains compose a protein
chains compose a protein
 proteins provide the
proteins provide the
“blueprints” for our
“blueprints” for our
characteristics and
characteristics and
functions.
functions.