Consider the following techniques/phenomena: 1. Budding and grafting in fruit plants 2. Cytoplasmic male sterility 3. Gene silencing Which of the above is/are used to create transgenic crops?
Contents12
- A1 only
- B2 and 3 only
- C1 and 3 only
- DNone
Show answer
Answer: (B) 2 and 3 only
Transgenic crops = crops that have foreign genes inserted into them using genetic engineering.
(1) Budding and grafting — WRONG: These are traditional horticultural techniques that join two plant parts physically.
No gene transfer happens — the rootstock and scion keep their own DNA.
Not transgenic.
(2) Cytoplasmic male sterility (CMS) — CORRECT: CMS is used in transgenic crop development to prevent pollen formation, helping create hybrid seeds and acting as a biological containment tool for transgenic plants.
(3) Gene silencing (RNA interference) — CORRECT: This is a core genetic engineering technique used to 'switch off' specific genes in transgenic crops (e.g., silencing genes that cause browning in apples, or pest-susceptibility genes).
Both 2 and 3 are biotechnology tools used specifically in transgenic crop creation.
Transgenic crops contain foreign genes inserted through genetic engineering, unlike traditional breeding methods that work with existing plant genetics.
UPSC is testing whether students can distinguish between traditional agricultural techniques (grafting) and modern biotechnology tools (gene silencing and cytoplasmic male sterility).
Transgenic Crops & Genetic Engineering
Science And Technology transgenic crops gene silencing
Transgenic Crops: Definition, Methods & UPSC Testing Pattern
Transgenic crops contain foreign genes inserted through genetic engineering
Gene silencing (RNAi) switches off specific genes in transgenic plants
Traditional grafting does NOT create transgenic crops
CMS creates male-sterile plants for hybrid seed production
Transgenic crops are plants that have foreign DNA inserted into their genome using biotechnology techniques. This differs fundamentally from traditional breeding methods.
Transgenic vs Traditional Methods
Method | Gene Transfer | DNA Changes | Transgenic Status |
|---|---|---|---|
Gene Silencing (RNAi) | Yes - foreign genes inserted | Genome modified | Transgenic |
Cytoplasmic Male Sterility | Yes - engineered genes | Cytoplasm modified | Transgenic |
Budding & Grafting | No - physical joining only | No genome change | NOT Transgenic |
Traditional Breeding | No - sexual reproduction | Gene recombination only | NOT Transgenic |
Key Transgenic Techniques
Gene silencing (RNA interference) - Inserts genes that produce RNA molecules to 'switch off' target genes
Gene insertion - Adds completely new genes from other species (e.g., Bt toxin genes from bacteria)
Gene editing - Modifies existing genes using tools like CRISPR-Cas9
Marker genes - Added alongside desired genes to identify successfully transformed plants
Trap: Grafting sounds scientific but only joins plant parts physically - no DNA transfer occurs
Trap: CMS can be natural or engineered - only the engineered version creates transgenic crops
Confusion: Gene silencing doesn't delete genes - it prevents their expression using RNAi
Key distinction: Transgenic = foreign genes added; Traditional breeding = existing genes recombined
Cytoplasmic Male Sterility (CMS)
Science And Technology Cytoplasmic male sterility
Cytoplasmic Male Sterility: Mechanism & Applications in Crop Development
CMS prevents pollen formation in plants while keeping female parts functional
Used in hybrid seed production to avoid manual emasculation
Can be natural (not transgenic) or engineered (transgenic)
Cytoplasmic Male Sterility (CMS) is a condition where plants cannot produce functional pollen but remain female-fertile. This trait is controlled by genes in the cytoplasm, not the nucleus.
CMS in Hybrid Seed Production
%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
s1["`**CMS line created**
Plants engineered to be male-sterile`"]
s2["`**Cross-pollination**
CMS plants pollinated by fertile male parent`"]
s3["`**Hybrid seeds produced**
All seeds are hybrids (no self-pollination possible)`"]
s4["`**Containment achieved**
Transgenic plants cannot spread pollen`"]
s1 --> s2
s2 --> s3
s3 --> s4Applications in Biotechnology
Hybrid seed production - Eliminates need for manual removal of male parts (emasculation)
Biological containment - Prevents transgenic crops from spreading through pollen
Cost reduction - Automates hybrid seed production process
Research tool - Used in studying gene function and plant reproduction
Natural vs Engineered: Natural CMS exists but engineered CMS creates transgenic crops
Male sterile ≠ completely sterile: Plants can still produce seeds as female parent
Cytoplasm location: CMS genes are in cytoplasm, not nuclear DNA
Gene Silencing & RNA Interference
Science And Technology Gene silencing
Gene Silencing (RNAi): Mechanism & Applications in Transgenic Crops
Gene silencing uses RNA molecules to 'switch off' specific genes without deleting them
RNAi (RNA interference) is the main mechanism for gene silencing
Does NOT delete genes - only prevents their expression
Used to remove unwanted traits in transgenic crops
Gene silencing is a biotechnology technique that prevents specific genes from being expressed (turned on) without removing them from the genome. It works by introducing RNA molecules that interfere with gene expression.
RNA Interference Mechanism
%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
s1["`**Foreign gene inserted**
Transgenic plant contains RNAi construct`"]
s2["`**RNA molecules produced**
Small interfering RNAs (siRNAs) are made`"]
s3["`**Target mRNA blocked**
siRNAs bind to complementary mRNA sequences`"]
s4["`**Gene silenced**
Target gene cannot produce proteins`"]
s1 --> s2
s2 --> s3
s3 --> s4Gene Silencing Applications
Crop Example | Gene Silenced | Result Achieved |
|---|---|---|
Arctic Apples | Polyphenol oxidase (PPO) | Non-browning apples |
Bt Cotton | Pest susceptibility genes | Enhanced insect resistance |
Golden Rice | Genes blocking vitamin A | Higher vitamin A content |
Roundup Ready Crops | Herbicide sensitivity genes | Herbicide tolerance |
Silencing ≠ Deletion: Genes remain in DNA but cannot function
RNA, not DNA: Uses RNA molecules as the silencing agent
Always transgenic: Gene silencing requires inserting foreign RNAi constructs
Budding & Grafting Techniques
Science And Technology Budding and grafting
Budding & Grafting: Traditional Techniques vs Genetic Engineering
Budding & grafting are physical joining techniques, not genetic engineering
No gene transfer occurs - each part keeps its original DNA
NOT transgenic - no foreign genes involved
Used in fruit trees, roses, and ornamental plants
Budding and grafting are traditional horticultural techniques that physically join parts from two different plants. The rootstock (root system) and scion (upper part) remain genetically distinct.
Grafting vs Genetic Engineering
Aspect | Budding/Grafting | Genetic Engineering |
|---|---|---|
Method | Physical joining of plant parts | DNA manipulation in laboratory |
Gene Transfer | No - parts keep original DNA | Yes - foreign genes inserted |
Tools Required | Knife, tape, horticultural skills | Specialized lab equipment, enzymes |
Result | Two genotypes in one plant | Single modified genotype |
Transgenic Status | NOT transgenic | Transgenic |
Why Grafting is Used
Disease resistance - Combine resistant rootstock with desirable fruit variety
Soil adaptation - Use rootstock adapted to local soil conditions
Size control - Dwarf rootstocks create smaller fruit trees
Multiple varieties - Graft different cultivars onto single rootstock
UPSC trap: Grafting sounds like biotechnology but it's purely mechanical
No DNA mixing: Rootstock and scion maintain separate genetic identities
Ancient technique: Practiced for thousands of years, predates genetic engineering