Molecular markers & genomics
Molecular Marker: A DNA sequence associated with a specific gene or trait, used to identify individuals with that trait.
Types of Markers:
- Morphological markers – Color, shape
- Biochemical markers – Isozymes
- Molecular markers – RFLP, RAPD, SSR, SNP
|
Marker |
Full form |
Key Point |
|
RFLP |
Restriction Fragment Length Polymorphism |
First DNA marker used |
|
RAPD |
Random Amplified Polymorphic DNA |
Fast, less reliable |
|
SSR |
Simple Sequence Repeat (Microsatellite) |
Highly reproducible |
|
SNP |
Single Nucleotide Polymorphism |
Single base change marker |
Applications:
- Genetic diversity analysis
- Marker-Assisted Selection (MAS)
- Gene mapping
- Identification of hybrids
Fact:
- Human Genome Project completed in 2003.
- Rice genome sequencing completed in 2005 (IRGSP).
Biofertilizers & biopesticides
Biofertilizers: Microorganisms that enhance nutrient availability to plants.
|
Type |
Microorganism |
Function |
|
Nitrogen fixers |
Rhizobium, Azospirillum |
N fixation |
|
Phosphate solubilizers |
Pseudomonas, Bacillus |
P solubilization |
|
Potassium solubilizers |
Bacillus mucilaginosus |
K availability |
|
Mycorrhizae |
Glomus spp. |
P absorption |
|
Cyanobacteria |
Anabaena, Nostoc |
N fixation in rice fields |
Biopesticides: Biological agents used to control pests/diseases.
|
Type |
Example |
Target |
|
Bacterial |
Bacillus thuringiensis |
Lepidopteran insects |
|
Viral |
NPV, GV |
Caterpillars |
|
Fungal |
Beauveria bassiana, Metarhizium |
Soil insects |
|
Botanical |
Neem (Azadirachtin) |
Broad-spectrum repellent |
Molecular diagnostics
Used for:
- Pathogen detection
- Genetic purity testing
- Disease resistance screening
Techniques:
- PCR (Polymerase Chain Reaction) – Amplifies DNA.
- ELISA (Enzyme Linked Immunosorbent Assay) – Detects proteins/antigens.
- Southern/Northern/Western Blotting – Detect DNA/RNA/proteins respectively.
Fact: PCR discovered by Kary Mullis (1983).
Genome editing technologies
CRISPR-Cas9 Technology: A genome editing tool for precise modification of DNA sequences.
- Discovered from bacterial immune system.
- Components:
- Cas9 enzyme – acts as molecular scissors.
- Guide RNA (gRNA) – directs Cas9 to target DNA.
- Advantages: High accuracy, cheap, easy to use.
Other Genome Editing Tools:
- ZFN (Zinc Finger Nuclease)
- TALEN (Transcription Activator-like Effector Nuclease)
Biosafety and regulatory bodies (india)
|
Agency |
Full Name |
Function |
|
DBT |
Department of Biotechnology |
Policy & funding |
|
GEAC |
Genetic Engineering Appraisal Committee |
Approval of GM crops |
|
RCGM |
Review Committee on Genetic Manipulation |
Monitors lab-level trials |
|
IBSC |
Institutional Biosafety Committee |
Safety at institutional level |
|
NBA |
National Biodiversity Authority |
Regulates genetic resources |
Fact: Biosafety Guidelines released by DBT in 1990, 1998, 2017.
Important scientists & discoveries
|
Discovery |
Scientist |
|
Term “Biotechnology” |
Karl Ereky (1919) |
|
Restriction enzyme |
Hamilton Smith |
|
Recombinant DNA |
Stanley Cohen & Herbert Boyer |
|
Agrobacterium-mediated transformation |
Jeff Schell & Marc Van Montagu |
|
Ti plasmid |
Agrobacterium tumefaciens |
|
PCR |
Kary Mullis (1983) |
|
Golden Rice |
Ingo Potrykus & Peter Beyer |
|
Bt toxin gene |
Bacillus thuringiensis |
|
CRISPR |
Jennifer Doudna & Emmanuelle Charpentier |
Key facts for exam
- First transgenic plant: Tobacco (1983).
- First GM crop approved in India: Bt Cotton (2002).
- Ti plasmid is a natural vector used in plant genetic engineering.
- Selectable markers: nptII, hpt, bar genes.
- Gene gun (biolistics) used for direct gene transfer into plants.
- Agrobacterium-mediated transformation – indirect gene transfer method.
- Cry genes in Bt – provide insecticidal properties.
- Golden Rice – Biofortified with β-carotene (Pro-vitamin A).
- Bt Brinjal – First GM food crop approved in India (not commercially released).
- Somaclonal variation – Genetic variation among tissue culture plants.
