Consider the following statements: 1. Genetic changes can be introduced in the cells that produce eggs or sperms of a prospective parent. 2. A person's genome can be edited before birth at the early embryonic stage. 3. Human induced pluripotent stem cells can be injected into the embryo of a pig. Which of the statements given above is/are correct?
Contents22
- A1 only
- B2 and 3 only
- C2 only
- D1, 2 and 3
Show answer
Answer: (D) 1, 2 and 3
This question is about three cutting-edge biotechnologies.
Let's break each one down simply:
Statement 1 (Genetic changes in egg/sperm cells) — CORRECT: This is called "germline gene therapy."
Scientists can modify the DNA in cells that produce eggs or sperm.
This means the changes would be passed on to future generations.
It's a real technology, though it raises ethical concerns.
Statement 2 (Editing genome before birth) — CORRECT: Using tools like CRISPR, scientists can edit an embryo's DNA at a very early stage.
This is different from germline therapy and can potentially eliminate inherited diseases before a baby is born.
Statement 3 (Human stem cells in pig embryo) — CORRECT: Scientists have actually injected human induced pluripotent stem cells (iPSCs) into pig embryos.
This creates what's called a "human-animal chimera."
The goal is to eventually grow human organs inside animals for transplant purposes.
Research showed that intermediate human pluripotent stem cells survived the longest in pig embryos.
All three statements are correct, so the answer is D.
Key Takeaway:
Statement 1 = editing reproductive cells,
Statement 2 = editing embryo DNA,
Statement 3 = human-pig chimera research.
All are real technologies.
Gene editing technologies like CRISPR became major scientific breakthroughs around 2018-2020, with the first gene-edited babies born in China and ongoing chimera research for organ transplants.
UPSC is testing whether students can distinguish between three different gene editing approaches: germline therapy (editing reproductive cells), embryonic gene editing (editing before birth), and chimera creation (mixing human-animal cells).
Germline Gene Therapy
Science And Technology Genetic changes eggs sperms prospective parent
Germline Gene Therapy: Editing Reproductive Cells
Germline therapy modifies DNA in egg or sperm cells — changes pass to offspring
Uses CRISPR-Cas9 and other gene editing tools to alter reproductive cell DNA
Different from somatic therapy which only affects the treated individual
Raises major ethical concerns about permanent genetic changes in human species
What It Means
Germline gene therapy targets the germ cells — cells that produce eggs and sperm. Unlike regular gene therapy that treats existing diseases in a person's body, germline editing creates permanent changes that pass to future generations.
Germline vs Somatic Therapy
Therapy Type | Target Cells | Inheritance | Current Status | Key Use |
|---|---|---|---|---|
Germline | Egg/sperm cells | Heritable — passes to children | Research stage, ethical barriers | Prevent genetic diseases in future generations |
Somatic | Body cells (non-reproductive) | Non-heritable — dies with patient | Clinical trials ongoing | Treat existing diseases in individuals |
Technical Process
Scientists extract gametes (egg/sperm precursor cells) from reproductive organs
CRISPR-Cas9 cuts specific DNA sequences and inserts corrected genetic material
Modified cells are used in IVF procedures to create embryos with edited genes
The embryo carries the genetic changes in every cell, including future reproductive cells
Don't confuse germline (reproductive cells) with somatic (body cells) — Statement 1 specifically mentions egg/sperm
Germline editing is technically possible but faces ethical restrictions — the statement asks if it CAN be done, not if it SHOULD be
Changes in germline therapy are permanent and heritable — this distinguishes it from regular gene therapy
Embryonic Gene Editing
Science And Technology genome edited before birth early embryonic stage
Embryonic Gene Editing: Modifying DNA Before Birth
Early embryo genome editing uses CRISPR-Cas9 to modify DNA in first few cell divisions
Done at blastocyst stage (5-6 days) when embryo has 50-100 cells
Can potentially eliminate inherited diseases like sickle cell anemia
He Jiankui case (2018) — first gene-edited babies born in China, caused global controversy
The Technology
Embryonic gene editing modifies DNA during the earliest stages of human development. Scientists use CRISPR-Cas9 to cut and replace faulty genes in embryos created through IVF, before implanting them in the mother's womb.
Embryo Editing Process
%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
s1["`****IVF Creation****
Egg and sperm combined in laboratory to form embryo`"]
s2["`****Early Stage Targeting****
CRISPR injected when embryo has just 2-8 cells`"]
s3["`****DNA Modification****
Faulty genes cut out and replaced with healthy sequences`"]
s4["`****Cell Division****
All subsequent cells carry the edited genetic code`"]
s5["`****Implantation****
Modified embryo transferred to mother's uterus for development`"]
s1 --> s2
s2 --> s3
s3 --> s4
s4 --> s5Key Applications
Eliminate single-gene disorders like Huntington's disease, cystic fibrosis, beta-thalassemia
Reduce risk of hereditary cancers by removing cancer-predisposing gene variants
Potential to enhance disease resistance — HIV resistance through CCR5 gene modification
Research into preventing mitochondrial diseases through three-parent IVF techniques
Before birth editing is technically feasible — Statement 2 asks about capability, not ethics
Don't confuse with gene therapy after birth — this specifically targets embryonic stage
Early embryonic stage means first few days/weeks, not late pregnancy
Human-Animal Chimeras
Science And Technology Human induced pluripotent stem cells injected embryo pig
Human-Animal Chimeras: Cross-Species Cell Integration
Human iPSCs can be injected into pig embryos to create human-pig chimeras
Goal is to grow human organs inside animals for transplantation
Chimera = organism containing cells from two different species
Research led by Juan Carlos Izpisua Belmonte at Salk Institute
The Science
Human-animal chimeras are created by injecting human induced pluripotent stem cells (iPSCs) into early-stage animal embryos. The human cells integrate with animal cells and can potentially develop into human organs within the animal host.
Chimera Research Models
Animal Host | Success Rate | Key Finding | Research Goal |
|---|---|---|---|
Pig | Low but detectable | Human cells survive longest in intermediate pluripotent state | Grow human hearts, kidneys for transplant |
Monkey | Higher integration | Better developmental compatibility with human cells | Study human brain development |
Mouse | Moderate success | Proof of concept established first | Test gene editing techniques |
Sheep | Limited success | Size compatibility with human organs | Alternative to pig models |
Technical Challenges
Species barrier — human and pig cells have different developmental timelines
Immune rejection — pig immune system may attack human cells
Ethical concerns — risk of human cells contributing to animal brain or reproductive organs
Low efficiency — most injected human cells fail to integrate successfully
Chimera Creation Process
%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
s1["`****iPSC Preparation****
Human skin cells reprogrammed into pluripotent stem cells`"]
s2["`****Embryo Collection****
Early-stage pig embryos (blastocysts) obtained`"]
s3["`****Cell Injection****
10-15 human iPSCs injected into pig embryo`"]
s4["`****Implantation****
Modified embryo transferred to surrogate pig mother`"]
s5["`****Development Monitoring****
Track human cell survival and organ formation`"]
s1 --> s2
s2 --> s3
s3 --> s4
s4 --> s5Statement 3 is factually correct — this research has actually been conducted and published
Don't assume impossible because it sounds like science fiction — human-pig chimeras are real
iPSCs (induced pluripotent stem cells) are different from embryonic stem cells — they're reprogrammed adult cells
CRISPR & Gene Editing Tools
Science And Technology
CRISPR-Cas9: The Molecular Scissors Revolutionizing Genetics
CRISPR-Cas9 = programmable molecular scissors that cut and edit DNA precisely
Developed from bacterial immune system — bacteria use it to fight viruses
Can edit genes in any cell type — embryos, adults, plants, animals
Jennifer Doudna and Emmanuelle Charpentier won 2020 Nobel Prize for CRISPR
How It Works
CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats. It uses a guide RNA to locate specific DNA sequences and the Cas9 enzyme to cut them. Scientists can then insert, delete, or replace genetic material at that exact location.
CRISPR Mechanism
%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
s1["`****Guide RNA Design****
Scientists create RNA sequence matching target DNA`"]
s2["`****Target Recognition****
Guide RNA finds and binds to specific DNA sequence`"]
s3["`****Cas9 Cutting****
Cas9 enzyme cuts both strands of DNA at target site`"]
s4["`****DNA Repair****
Cell's repair system fixes the cut — scientists can insert new genes here`"]
s5["`****Gene Expression****
Modified DNA produces new proteins according to edits`"]
s1 --> s2
s2 --> s3
s3 --> s4
s4 --> s5Gene Editing Applications
Application Area | Current Status | Key Examples | Timeline |
|---|---|---|---|
Medical Therapy | Clinical trials | Sickle cell treatment, cancer immunotherapy | 2-5 years |
Agricultural Crops | Commercial use | Drought-resistant crops, enhanced nutrition | Already available |
Research Models | Widespread use | Disease modeling in mice, drug testing | Currently used |
Conservation | Experimental | Mosquito population control, coral restoration | 10+ years |
CRISPR is the system, Cas9 is the cutting enzyme — they work together but are different components
Not just for humans — CRISPR works on all organisms including plants, bacteria, animals
Guide RNA is programmable — scientists can target any DNA sequence by changing the RNA design
Induced Pluripotent Stem Cells
Science And Technology induced pluripotent stem cells
Induced Pluripotent Stem Cells: Reprogramming Adult Cells
iPSCs are adult cells reprogrammed to behave like embryonic stem cells
Created using Yamanaka factors — four key proteins that reset cell identity
Can become any cell type in the body — neurons, heart cells, liver cells
Shinya Yamanaka won 2012 Nobel Prize for discovering iPSC reprogramming
Revolutionary Concept
Induced pluripotent stem cells (iPSCs) solve the ethical problems of embryonic stem cell research. Scientists take ordinary adult cells like skin cells and use genetic reprogramming to make them pluripotent — capable of becoming any cell type in the body.
Stem Cell Types Comparison
Cell Type | Source | Pluripotency | Ethical Issues | Clinical Use |
|---|---|---|---|---|
Embryonic Stem Cells | Early embryos | Fully pluripotent | High — destroys embryos | Limited due to ethics |
Adult Stem Cells | Bone marrow, fat | Limited — only certain cell types | None | Currently used |
iPSCs | Any adult cell | Fully pluripotent | None — no embryos needed | Clinical trials |
Fetal Stem Cells | Fetal tissue | Moderately pluripotent | Moderate | Research only |
iPSC Creation Process
%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
s1["`****Cell Collection****
Take skin cells or blood cells from patient`"]
s2["`****Yamanaka Factors****
Insert 4 reprogramming genes (Oct4, Sox2, Klf4, c-Myc)`"]
s3["`****Reprogramming****
Cells gradually lose adult identity over 2-3 weeks`"]
s4["`****iPSC Formation****
Cells become pluripotent — can make any cell type`"]
s5["`****Differentiation****
Direct iPSCs to become desired cell type for therapy`"]
s1 --> s2
s2 --> s3
s3 --> s4
s4 --> s5Medical Applications
Personalized medicine — create patient-specific cells that won't be rejected
Disease modeling — study genetic diseases in lab-grown patient cells
Drug testing — test medicines on human cells before clinical trials
Organ regeneration — potentially grow replacement organs from patient's own cells
iPSCs are NOT embryonic stem cells — they're reprogrammed adult cells with embryonic-like properties
Statement 3 uses iPSCs specifically — this distinguishes from other stem cell types
iPSCs can be made from any adult cell — skin, blood, hair follicles all work