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In the context of recent advances in human reproductive technology, "Pronuclear Transfer" is used for
Explanation
The correct answer is Option 4: prevention of mitochondrial diseases in offspring.
Pronuclear Transfer (PT) is a form of Mitochondrial Replacement Therapy (MRT), colloquially known as "three-parent baby" technology. It is specifically designed to prevent the mother from passing on debilitating mitochondrial DNA (mtDNA) mutations to her child.
- Mechanism: In this process, the mother’s egg is fertilized with the father’s sperm in vitro. The resulting pronuclei (nuclear genetic material) are then removed and transferred into a donor egg that has had its own nucleus removed but retains healthy mitochondria.
- Outcome: The embryo contains the nuclear DNA of both parents (determining physical traits) but the healthy mitochondrial DNA of the donor.
- Distinction: Unlike Option 1, it is not a routine IVF procedure. Unlike Option 2, it does not involve germline modification of sperm. Unlike Option 3, it focuses on disease prevention in live births rather than stem cell research.
Thus, PT is a critical intervention for ensuring that offspring are born free of inherited mitochondrial disorders.
PROVENANCE & STUDY PATTERN
Guest previewThis is a classic 'Science in the Headlines' question. While technically complex, the term 'Pronuclear Transfer' was synonymous with the 'Three-Parent Baby' controversy that dominated science news from 2016 to 2019. If you relied only on static biology books, this was a bouncer; if you tracked major biotech breakthroughs, it was a sitter.
This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.
Web source
Presence: 5/5
"Mitochondrial donation by pronuclear transfer involves transplantation of nuclear genome from a fertilized egg from the affected woman to an enucleated fertilized egg donated by an unaffected woman."
Why this source?
- Defines pronuclear transfer as transplantation of the nuclear genome between fertilized eggs (one from the affected woman and one donated by an unaffected woman).
- Indicates the procedure operates on already-fertilized eggs, so it is not a technique that itself fertilizes an egg using donor sperm.
Web source
Presence: 4/5
"clinical pregnancies were confirmed in 8 of 22 patients (36%) ... who underwent an intracytoplasmic sperm injection procedure for pronuclear transfer or for PGT, respectively."
Why this source?
- States that intracytoplasmic sperm injection (ICSI) was performed in patients who underwent pronuclear transfer, showing fertilization (by ICSI) occurs prior to the pronuclear transfer step.
- Does not describe pronuclear transfer as a method that fertilizes eggs with donor sperm; instead fertilization is a separate step (ICSI) before nuclear transfer.
- Defines pronuclear transfer as transplantation of the nuclear genome between fertilized eggs (one from the affected woman and one donated by an unaffected woman).
- Indicates the procedure operates on already-fertilized eggs, so it is not a technique that itself fertilizes an egg using donor sperm.
- States that intracytoplasmic sperm injection (ICSI) was performed in patients who underwent pronuclear transfer, showing fertilization (by ICSI) occurs prior to the pronuclear transfer step.
- Does not describe pronuclear transfer as a method that fertilizes eggs with donor sperm; instead fertilization is a separate step (ICSI) before nuclear transfer.
Science , class X (NCERT 2025 ed.) > Chapter 7: How do Organisms Reproduce? > What you have learnt > p. 126
Strength: 4/5
“This is followed by fertilisation.• n Changes in the body at puberty, such as increase in breast size in girls and new facial hair growth in boys, are signs of sexual maturation.• n The male reproductive system in human beings consists of testes which produce sperms, vas deferens, seminal vesicles, prostate gland, urethra and penis.• n The female reproductive system in human beings consists of ovaries, fallopian tubes, uterus and vagina.• n Sexual reproduction in human beings involves the introduction of sperm in the vagina of the female. Fertilisation occurs in the fallopian tube.• n Contraception to avoid pregnancy can be achieved by the use of condoms, oral pills, copper-T and other methods.”
Why relevant
States where fertilisation normally occurs in humans (sperm introduced into vagina, fertilisation in fallopian tube), establishing the basic biological sites and agents (sperm + egg) involved in conception.
How to extend
A student could use this to contrast natural (in vivo) fertilisation locations with assisted techniques (in vitro) and ask whether pronuclear transfer relates to changing the location or source of gametes.
Science , class X (NCERT 2025 ed.) > Chapter 7: How do Organisms Reproduce? > 7.3.3 (b) Female Reproductive System > p. 124
Strength: 3/5
“When a girl is born, the ovaries already contain thousands of immature eggs. On reaching puberty, some of these start maturing. One egg is produced every month by one of the ovaries. The egg is carried from the ovary to the womb through a thin oviduct or fallopian tube. The two oviducts unite into an elastic bag-like structure known as the uterus. The uterus opens into the vagina through the cervix. The sperms enter through the vaginal passage during sexual intercourse. They travel upwards and reach the oviduct where they may encounter the egg. The fertilised egg (zygote) starts dividing and form a ball of cells or embryo.”
Why relevant
Describes the female reproductive tract and the normal journey of an egg to the oviduct where sperm encounter it and fertilisation occurs.
How to extend
One can extend this to note that assisted methods must replicate or replace this meeting of gametes (e.g., IVF) and then consider whether pronuclear transfer is a step that involves donor sperm or manipulation after fertilisation.
Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 13: Our Home: Earth, a Unique Life Sustaining Planet > Sexual reproduction in animals > p. 222
Strength: 3/5
“Fig. 13.14: Formation of zygote
222
In animals, gametes are called sperm (male) and eggs (female). Fertilisation may take place in water, for example, male and female fish or frogs eject sperm and eggs, respectively, into the water where they combine to form the zygote. In these animals, the development of the zygote into an embryo also takes place in water (Fig. 13.14).
In birds and mammals, including humans, sperm are deposited inside the female and fertilisation takes place when the sperm swim towards the egg produced by the female. After this step, birds and mammals follow different processes.”
Why relevant
Explains that in mammals sperm are deposited inside the female and fertilisation takes place when sperm swim towards the egg, highlighting that fertilisation is an encounter of two gametes.
How to extend
A student could compare this standard gamete encounter with technologies that perform fertilisation outside the body (in vitro) and then question whether pronuclear transfer is itself the act of fertilisation or a subsequent manipulation.
Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 29: Environment Issues and Health Effects > 29.3.4. Greeenwashing > p. 422
Strength: 4/5
“In animals, this is the freezing of sperm and eggs in zoological freezers until further need. • Biobank is a cryogenic storage facility used to archive biological samples for use in research and experiments. • Xero*ere is a plant succession which is limited by water availability. It includes the different stages in a research succession. All Rights Reserved. No part of this material may be reproduced in any form or by any means without permission in writing.”
Why relevant
Mentions freezing of sperm and eggs and biobanks for storage, showing that reproductive cells are handled and stored in assisted-reproduction contexts.
How to extend
Using this, a student might infer that assisted reproductive technologies manipulate gametes/zygotes and thus investigate whether pronuclear transfer is one such manipulation involving donor gametes.
Science , class X (NCERT 2025 ed.) > Chapter 7: How do Organisms Reproduce? > 7.3.3 (d) Reproductive Health > p. 125
Strength: 2/5
“These drugs commonly need to be taken orally as pills. However, since they change hormonal balances, they can cause side-effects too. Other contraceptive devices such as the loop or the copper-T are placed in the uterus to prevent pregnancy. Again, they can cause side effects due to irritation of the uterus. If the vas deferens in the male is blocked, sperm transfer will be prevented. If the fallopian tube in the female is blocked, the egg will not be able to reach the uterus. In both cases fertilisation will not take place. Surgical methods can be used to create such blocks.”
Why relevant
Notes that blocking the fallopian tube or vas deferens prevents sperm and egg meeting and thus fertilisation doesn't take place, reinforcing that fertilisation requires union of gametes and can be disrupted or bypassed.
How to extend
A student could extend this to consider that medical interventions can redirect fertilisation (e.g., IVF) and then ask whether pronuclear transfer is an alternative method that uses donor sperm or works after fertilisation.
States where fertilisation normally occurs in humans (sperm introduced into vagina, fertilisation in fallopian tube), establishing the basic biological sites and agents (sperm + egg) involved in conception.
A student could use this to contrast natural (in vivo) fertilisation locations with assisted techniques (in vitro) and ask whether pronuclear transfer relates to changing the location or source of gametes.
Describes the female reproductive tract and the normal journey of an egg to the oviduct where sperm encounter it and fertilisation occurs.
One can extend this to note that assisted methods must replicate or replace this meeting of gametes (e.g., IVF) and then consider whether pronuclear transfer is a step that involves donor sperm or manipulation after fertilisation.
Explains that in mammals sperm are deposited inside the female and fertilisation takes place when sperm swim towards the egg, highlighting that fertilisation is an encounter of two gametes.
A student could compare this standard gamete encounter with technologies that perform fertilisation outside the body (in vitro) and then question whether pronuclear transfer is itself the act of fertilisation or a subsequent manipulation.
Mentions freezing of sperm and eggs and biobanks for storage, showing that reproductive cells are handled and stored in assisted-reproduction contexts.
Using this, a student might infer that assisted reproductive technologies manipulate gametes/zygotes and thus investigate whether pronuclear transfer is one such manipulation involving donor gametes.
Notes that blocking the fallopian tube or vas deferens prevents sperm and egg meeting and thus fertilisation doesn't take place, reinforcing that fertilisation requires union of gametes and can be disrupted or bypassed.
A student could extend this to consider that medical interventions can redirect fertilisation (e.g., IVF) and then ask whether pronuclear transfer is an alternative method that uses donor sperm or works after fertilisation.
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