With reference to the recent developments in science, which one of the following statements is not correct?
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- AFunctional chromosomes can be created by joining segments of DNA taken from cells of different species.
- BPieces of artificial functional DNA can be created in laboratories.
- CA piece of DNA taken out from an animal cell can be made to replicate outside a living cell in a laboratory.
- DCells taken out from plants and animals can be made to undergo cell division in laboratory petri dishes.
Show answer
Answer: (A) Functional chromosomes can be created by joining segments of DNA taken from cells of different species.
The correct answer is (A) — this is the INCORRECT statement.
You CANNOT create functional chromosomes by joining DNA segments from different species.
Options B, C, and D are all scientifically correct:
- artificial DNA can be made in labs (B),
- DNA can replicate outside living cells using techniques like PCR (C),
- and plant/animal cells can divide in lab petri dishes through cell culture (D).
Tip: DNA from different species won't form a working chromosome — chromosomes need species-specific organization to function.
DNA can be artificially synthesized, amplified through PCR, and cultured in laboratories, but functional chromosomes cannot be created by simply joining DNA segments from different species.
CRISPR gene editing and synthetic biology developments in 2018-2019 made biotechnology techniques a current affairs focus, prompting questions on what is actually possible versus impossible in genetic engineering.
The question tests the boundary between what biotechnology can and cannot do - students must distinguish between basic DNA manipulation versus complex chromosome assembly.
Functional Chromosomes & DNA Segments
Science And Technology Functional chromosomes DNA taken from cells different species
Functional Chromosomes: Why Cross-Species DNA Won't Work
Functional chromosomes cannot be created by joining DNA from different species
Chromosomes need species-specific organization (centromeres, telomeres, histones) to function
Recombinant DNA can be made from different species, but not entire functional chromosomes
Why This Fails
A functional chromosome requires precise species-specific organization — centromeres for division, telomeres for protection, and compatible histone proteins. Simply joining DNA segments from different species creates a genetic construct, not a working chromosome that can replicate and segregate properly during cell division.
What Works vs What Doesn't
Technique | Cross-Species Possible? | Example | Why It Works/Fails |
|---|---|---|---|
Recombinant DNA | ✓ Yes | Human insulin gene in bacteria | Single genes can function across species |
Functional Chromosomes | ✗ No | Mixing human + plant DNA | Chromosome structure is species-specific |
Gene Cloning | ✓ Yes | GFP gene in multiple organisms | Individual genes are portable |
Chromosome Engineering | ✗ No | Hybrid chromosomes | Centromeres, telomeres won't be compatible |
Trap: Confusing recombinant DNA (which works across species) with functional chromosomes (which don't)
Trap: Thinking 'functional' just means 'containing genes' — it means the chromosome can actually replicate and divide
Key Word: 'Functional chromosomes' ≠ 'functional genes' — chromosomes need structural compatibility
Artificial DNA Synthesis
Science And Technology artificial functional DNA created in laboratories
Artificial DNA Synthesis: Laboratory Creation of Functional DNA
Artificial functional DNA can be created in laboratories using chemical synthesis
Oligonucleotides are chemically synthesized DNA pieces up to ~200 base pairs
Entire synthetic genomes have been created for simple organisms like bacteria
How It Works
DNA synthesis uses automated machines to chemically assemble nucleotides (A, T, G, C) in any desired sequence. This creates oligonucleotides — short DNA pieces that are fully functional for PCR primers, gene probes, or building blocks for larger constructs.
Applications & Examples
PCR primers — custom DNA sequences designed to amplify specific genes
Gene synthesis — creating genes that don't exist in nature for research
Synthetic biology — engineering organisms with entirely artificial genetic circuits
Mycoplasma mycoides — first organism with a completely synthetic genome (2010)
DNA data storage — encoding digital information in synthetic DNA sequences
Don't confuse: Artificial DNA synthesis (creating new sequences) vs DNA cloning (copying existing sequences)
Functional means the synthesized DNA actually works — it's not just random nucleotides
DNA Replication Outside Living Cells
Science And Technology DNA taken out from animal cell replicate outside a living cell
DNA Replication Outside Living Cells: PCR & In Vitro Methods
DNA can replicate outside living cells using PCR and other in vitro methods
PCR amplifies specific DNA sequences using repeated heating and cooling cycles
Taq polymerase is the heat-stable enzyme that makes PCR possible
The Breakthrough
Polymerase Chain Reaction (PCR) revolutionized molecular biology by allowing DNA replication in test tubes. Extracted DNA from any source — blood, hair, ancient specimens — can be amplified millions of times without living cells.
PCR Process
%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
s1["`****Denaturation** (95°C)**
Heat separates DNA double helix into single strands`"]
s2["`****Annealing** (50-60°C)**
Primers bind to target sequences on single strands`"]
s3["`****Extension** (72°C)**
Taq polymerase synthesizes new DNA strands`"]
s4["`****Repeat Cycle****
Each cycle doubles the DNA — 30 cycles = 1 billion copies`"]
s1 --> s2
s2 --> s3
s3 --> s4Applications
Forensic analysis — amplifying DNA from crime scene samples
Medical diagnosis — detecting genetic diseases and infections
Ancient DNA — studying extinct species from fossil samples
COVID-19 testing — RT-PCR amplifies viral RNA (converted to DNA first)
Cell Culture in Laboratory
Science And Technology Cells taken out from plants and animals cell division in laboratory petri dishes
Cell Culture: Growing Plant & Animal Cells in Laboratory
Plant and animal cells can divide in laboratory petri dishes through cell culture
Cells need sterile conditions and nutrient medium to survive and divide outside organisms
HeLa cells are famous human cancer cells cultured since 1951
Basic Principle
Cell culture involves growing isolated cells in controlled laboratory conditions. Cells are provided with nutrients, growth factors, and optimal temperature/pH to maintain their natural division cycles outside the parent organism.
Plant vs Animal Cell Culture
Aspect | Plant Cell Culture | Animal Cell Culture |
|---|---|---|
Growing Surface | Can grow in suspension | Need attachment surface (except blood cells) |
Nutrient Medium | MS medium with hormones (auxins, cytokinins) | DMEM/RPMI with serum and growth factors |
Contamination Risk | Lower (plant cells have cell walls) | Higher (animal cells more fragile) |
Applications | Tissue culture, micropropagation | Drug testing, vaccine production |
Famous Example | Carrot cells growing whole plants | HeLa cells for cancer research |
Major Applications
Vaccine production — growing viruses in cultured animal cells
Drug testing — testing toxicity on cultured human cells before clinical trials
Plant micropropagation — mass producing identical plants from single cells
Stem cell research — studying cell differentiation in controlled conditions
Cancer research — studying tumor cell behavior and testing treatments
Key point: Both plant AND animal cells can be cultured — not just one type
Petri dishes are specifically mentioned — this refers to standard laboratory cell culture, not just keeping cells alive temporarily
Recombinant DNA Technology
Science And Technology
Recombinant DNA Technology: Genetic Engineering Fundamentals
Recombinant DNA combines genetic material from different sources using restriction enzymes
Plasmids serve as vectors to carry foreign genes into host cells
Used to produce human insulin, growth hormone, and other medicines in bacteria
Core Concept
Recombinant DNA technology allows scientists to cut and paste genes between different organisms. Unlike creating functional chromosomes (which fails), individual genes can successfully function across species because the genetic code is universal.
Recombinant DNA Process
%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
s1["`****Isolation****
Extract target gene from donor organism`"]
s2["`****Cutting****
Use restriction enzymes to cut gene and plasmid vector`"]
s3["`****Joining****
DNA ligase joins gene to plasmid (recombinant DNA)`"]
s4["`****Transformation****
Insert recombinant plasmid into host cell (usually bacteria)`"]
s5["`****Expression****
Host cell produces the desired protein`"]
s1 --> s2
s2 --> s3
s3 --> s4
s4 --> s5Key Applications in India
Product | Gene Source | Host Organism | Indian Company/Research |
|---|---|---|---|
Human Insulin | Human pancreas cells | E. coli bacteria | Biocon, Wockhardt |
Bt Cotton | Bacillus thuringiensis | Cotton plants | Mahyco, approved by GEAC |
Hepatitis B Vaccine | HBV surface antigen gene | Yeast cells | Serum Institute of India |
Growth Hormone | Human pituitary gland | E. coli bacteria | Various pharma companies |