This document discusses genetic chimerism, which occurs when an individual possesses two or more genetically distinct cell populations. It describes several types of chimerism including congenital chimerism from the fusion of fertilized eggs, dispermic chimerism from fertilization by two sperm, and microchimerism involving cells from a fetus. Examples of chimerism in animals like symbiotic chimerism in anglerfish and germline chimerism in marmosets are provided. The document also briefly discusses applications of chimerism and mentions the potential dangers of a hypothetical "Chimera virus" developed as a bioweapon.
1. Aniruddha Banerjee
Roll No.: 1110412200260002
Registration No.: 111171220035 of 2017-2018
5th Semester
Dept. Of Microbiology
Michael Madhusudan Memorial College
3. CHIMERISM
• It is a condition in which presence of two or more chromosomal complements
found in the same tissue of an individual.
• The divergent genotypes are usually found in all across the genome.
• It occurs in single organism composed of cells with distinct genotypes.
• Chimeras can happen with organ transplantation.
• It include possessing blood cells of different blood types, subtle variations in
form.
• If the zygotes were of differing sexes, then even the possession of both female
and male sex organs can occur.
6. CONGENITAL CHIMERISM
• Natural chimerism.
• Organism with mixed sexual
characteristics.
• May occur when two fertilized eggs
fuse together.
• Chromosome number- 46+XX/46+XY
• SRY gene gets transferred to the X
chromosome during meiosis.
• Organism developed are known as
Hermaphrodite.
7. DISPERMIC CHIMERISM
• Occurs due to fertilization of an oocyte and its second polar body by two
sperms.
• Also occur when a zygote fuses with a fertilized polar body.
• The organism developed from the zygote consist both type of genetic materials.
8. MICROCHIMERISM
• It is the presence of two genetically
distinct and separately derived
populations of cells.
• One population being at a low
concentration than other.
• The cells genetically distinct from
those of the host individual.
• Usually occurs to foetus from mother
• Results in the formation of various
autoimmune diseases.
9. TETRAGAMETIC CHIMERISM
• A type of congenital chimerism.
• Occurs due to fertilisation of two
separate ova by two sperm, followed
by aggregation of the two at
the blastocyst or zygote stages.
• Organism with intermingled cell
lines.
• Organism developed
possess organs that have different
sets of chromosomes.
11. SYMBIOTIC CHIMERISM
• Usually found in Angler fish
(Haplophryne mollis).
• The male releases an enzyme that
digests the skin of his mouth and the
body of the female.
• Results in the fusion of then down to
the blood-vessel level.
• Formation of single hermaphroditic
individual takes place.
• The male develops large testicles and
atrophy of other organs take place.
• Becomes able to have a greater number
of offspring.
12. GERMLINE CHIMERISM
• Occurs when the germ cells of an
organism are not genetically identical
to its own.
• Mainly found in marmosets.
• They carry the reproductive cells of
their fraternal twin siblings.
• Occurs because of placental fusion
during development.
14. Graft Chimerism
• Can be done by grafting genetically
different parents,
different cultivars or different species.
• Tissues gets partially fused together
following grafting.
• Example :- Laburnocytisus sp.
Chromosomal Chimerism
• These are chimeras in which the layers
differ in their chromosome constitution.
• Occasionally occurs due to loss or gain
of individual chromosomes or
chromosome fragments owing to miss-
division.
• It has various effects on cell size and
growth characteristics.
15. Nuclear Gene-differential
Chimerism
• These chimeras arise by spontaneous
or induced mutation of a nuclear gene
to a dominant or recessive allele.
• One character is affected at a time in
the leaf, flower, fruit, or other parts.
Plastid Gene-differential
Chimerism
• These arise by spontaneous or induced
mutation of a plastid gene.
• Plastids may sort-out from a mixed
egg or mixed zygote respectively.
• It affect the colour of the plasmids
within the leaves.
16. THE CHIMERA VIRUS
• It is the most lethal virus till date.
• Developed by Soviet Union in 1980 as “Project Chimera”.
• Virus was developed by combining DNA of Venezuelan Equine Encephalitis
Virus, Smallpox Virus and Ebola Virus.
• Developed as a bio-weapon.
• But the project was abandoned due to its significant risks.
17. APPLICATIONS
• Organ or stem cell transplantation.
• Tolerance to grafts and Graft versus Host Disease (GvHD).
• Prevention from Passenger Lymphocyte Syndrome(PLS) after transplantation.
• Tetragametic Chimerism applied in in-vitro fertilization.
• Can be useful for intrauterine diagnosis or prognosis.
• Can induce immunologic tolerance and possibly promote autoimmunity.
• Many fruits can be cultivated by grafting the body of a sapling onto
a rootstock.
• Has a huge potential to be used in bio-weapons development.
