Molecular Biology differences pdf 4th semester

Molecular Biology differences pdf 4th semester

1. BSc. Botany Honours | Core 8
*Molecular Biology
Important differences ….
Lecture - 10

2. DNA (Deoxyribonucleic Acid)
1.Structure: DNA is a double-stranded
helix consisting of deoxyribose sugar,
phosphate backbone, and nitrogenous
bases (adenine, thymine, cytosine,
guanine).
2.Function: DNA stores genetic information
used for the development, functioning,
and reproduction of living organisms.
3.Location: Primarily found in the cell
nucleus and also in mitochondria.
4.Stability: DNA is more stable and less
reactive compared to RNA due to the
absence of a hydroxyl group on the 2'
carbon of its sugar.
RNA (Ribonucleic Acid)
1.Structure: RNA is typically single-
stranded and consists of ribose sugar,
phosphate backbone, and nitrogenous
bases (adenine, uracil, cytosine,
guanine).
2.Function: RNA plays multiple roles
including coding, decoding, regulation,
and expression of genes (mRNA, tRNA,
rRNA).
3.Location: Found in the nucleus and
cytoplasm of cells.
4.Stability: RNA is less stable and more
reactive due to the presence of a
hydroxyl group on the 2' carbon of its
sugar.

3. B-DNA
1.Structure: Right-handed helical
structure with 10 base pairs per turn.
2.Helix Diameter: Approximately 2.0 nm.
3.Biological Role: Most common form of
DNA in cells under physiological
conditions.
4.Conformation: Major and minor grooves
are well-defined and accessible for
protein binding.
Z-DNA
1.Structure: Left-handed helical
structure with 12 base pairs per turn.
2.Helix Diameter: Approximately 1.8
nm.
3.Biological Role: Less common, often
found in regions of DNA undergoing
active transcription or where there is
high salt concentration.
4.Conformation: Zigzag backbone gives
it a unique appearance compared to B-
DNA.

4. mRNA (Messenger RNA)
1.Function: Carries genetic information
from DNA to the ribosome for protein
synthesis.
2.Structure: Linear and single-stranded
with a 5' cap and a poly-A tail.
3.Lifespan: Generally short-lived, ranging
from minutes to hours.
4.Location: Synthesized in the nucleus and
functions in the cytoplasm.
tRNA (Transfer RNA)
1.Function: Delivers amino acids to the
ribosome during protein synthesis.
2.Structure: Cloverleaf structure with
anticodon arm and amino acid
attachment site.
3.Lifespan: More stable and longer-lived
than mRNA.
4.Location: Present in the cytoplasm.

5. 70S Ribosomes
1.Location: Found in prokaryotes (bacteria
and archaea), as well as in mitochondria
and chloroplasts of eukaryotes.
2.Subunits: Composed of a 50S large
subunit and a 30S small subunit.
3.Function: Involved in protein synthesis in
prokaryotic cells.
4.Sensitivity: Targeted by certain
antibiotics (e.g., tetracycline).
80S Ribosomes
1.Location: Found in the cytoplasm of
eukaryotic cells.
2.Subunits: Composed of a 60S large
subunit and a 40S small subunit.
3.Function: Involved in protein synthesis
in eukaryotic cells.
4.Sensitivity: Not targeted by antibiotics
that affect 70S ribosomes.

6. Prokaryotic Replication
1.Origin: Begins at a single origin of
replication.
2.Speed: Generally faster due to less
complex regulatory mechanisms.
3.Enzymes: Uses fewer and simpler DNA
polymerases.
4.Structure: Occurs in circular DNA.
Eukaryotic Replication
1.Origin: Begins at multiple origins of
replication.
2.Speed: Slower due to more complex
regulatory mechanisms.
3.Enzymes: Involves multiple,
specialized DNA polymerases.
4.Structure: Occurs in linear DNA with
telomeres.

7. Prokaryotic Transcription &
Translation
1.Location: Both processes occur in the
cytoplasm.
2.Timing: Transcription and translation are
coupled (occur simultaneously).
3.RNA Processing: Minimal RNA processing;
mRNA is often used immediately after
synthesis.
4.Ribosomes: 70S ribosomes.
Eukaryotic Transcription &
Translation
1.Location: Transcription occurs in the
nucleus, and translation occurs in the
cytoplasm.
2.Timing: Processes are not coupled;
mRNA must be processed and
transported to the cytoplasm.
3.RNA Processing: Extensive RNA
processing including splicing, 5'
capping, and polyadenylation.
4.Ribosomes: 80S ribosomes.

8. Inducible Operon
1.Activation: Activated in the presence of
an inducer molecule.
2.Example: lac operon in E. coli.
3.Function: Typically involved in catabolic
pathways.
4.Regulation: Default state is off; turned
on by the presence of a substrate.
Repressible Operon
1.Activation: Deactivated in the
presence of a corepressor.
2.Example: trp operon in E. coli.
3.Function: Typically involved in
anabolic pathways.
4.Regulation: Default state is on; turned
off by the presence of the end product.

9. Inducer
1.Function: Molecule that initiates gene
expression by disabling a repressor.
2.Example: Allolactose in the lac operon.
3.Mechanism: Binds to the repressor,
preventing it from binding to the
operator.
4.Role: Activates transcription of specific
genes.
Repressor
1.Function: Protein that inhibits gene
expression by binding to the operator.
2.Example: Lac repressor in the lac
operon.
3.Mechanism: Binds to the operator to
block RNA polymerase.
4.Role: Deactivates transcription of
specific genes.

10. Euchromatin
1.Structure: Less condensed, more
accessible.
2.Activity: Actively transcribed regions of
DNA.
3.Staining: Lightly stained in microscopy.
4.Function: Associated with gene
expression.
Heterochromatin
1.Structure: Highly condensed, less
accessible.
2.Activity: Transcriptionally inactive
regions of DNA.
3.Staining: Darkly stained in microscopy.
4.Function: Associated with gene
repression and structural functions.

11. Constitutive Heterochromatin
1.Presence: Always present and usually
contains repetitive sequences.
2.Function: Structural roles, such as
maintaining chromosome integrity.
3.Example: Centromeres and telomeres.
4.Expression: Generally not transcribed.
Facultative Heterochromatin
1.Presence: Can form or de-condense
depending on the cell's needs.
2.Function: Regulates gene expression.
3.Example: X-chromosome inactivation
in females.
4.Expression: Can be transcriptionally
active under certain conditions.

12. Promoter Gene
1.Function: Site where RNA polymerase
binds to initiate transcription.
2.Location: Upstream of the gene to be
transcribed.
3.Sequence: Contains specific DNA
sequences like TATA box.
4.Role: Essential for starting gene
transcription.
Operator Gene
1.Function: Site where regulatory
proteins (repressors or activators)
bind.
2.Location: Usually found between the
promoter and the genes of an operon.
3.Sequence: Specific DNA sequence
recognized by repressor or activator.
4.Role: Regulates the transcription of
adjacent genes.

13. MtDNA (Mitochondrial DNA)
1.Location: Found in mitochondria.
2.Structure: Circular DNA molecule.
3.Inheritance: Maternally inherited.
4.Function: Encodes proteins involved in
mitochondrial function and energy
production.
CpDNA (Chloroplast DNA)
1.Location: Found in chloroplasts.
2.Structure: Circular DNA molecule.
3.Inheritance: Typically maternally
inherited (in plants).
4.Function: Encodes proteins involved in
photosynthesis and other chloroplast
functions.

14. Exon
1.Function: Coding regions of a gene that
are expressed.
2.Location: Remain in the mRNA after
splicing.
3.Role: Translate into proteins.
4.Presence: Found in both prokaryotic and
eukaryotic genes.
Intron
1.Function: Non-coding regions of a gene
that are spliced out.
2.Location: Removed from the pre-mRNA
during processing.
3.Role: Regulatory roles and alternative
splicing.
4.Presence: Predominantly found in
eukaryotic genes.

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