Endoreplication is a process where DNA replicates without cell division, leading to increased DNA content and polyploidy. It can be thought of as a variant of the cell cycle where mitosis is aborted prior to cytokinesis. While limited to specific cell types in animals, endoreplication is more widespread in plants and can be detected in most tissues. It serves as a universal developmental mechanism for differentiating and developing cell types with various functions. Examples include cell differentiation in plants, oogenesis, embryonic development, buffering against DNA damage, and stress response.

1. Endoreplication (endoreduplication or polytenization) is replication of the nuclear
genome in the absence of cell division, which leads to elevated nuclear gene
content and polyploidy.
Endoreplication can be understood simply as a variant form of the mitotic cell
cycle (G1-S-G2-M) in which mitosis is aborted prior to cytokinesis
Endoreplication is often limited to specific cell types in animals, it is considerably
more widespread in plants, such that polyploidy can be detected in the majority
of plant tissues.
Examples of endoreplication characterized in arthropod, mammalian, and
plant species suggest that it is a universal developmental mechanism
responsible for the differentiation and morphogenesis of cell types that fulfill
an array of biological functions.

3. Cell Differentiation: In developing plant tissues the transition from mitosis to
endoreplication often coincides with cell differentiation and morphogenesis.
Oogenesis and Embryonic Development: Endoreplication is commonly observed
in cells responsible for the nourishment and protection of oocytes and
embryos.
Buffering the Genome: Another intriguing hypothesis is that endoreplication
buffers against DNA damage and mutation because it provides extra copies of
important genes.[
Stress Response: Research in plants suggests that endoreplication may also
play a role in modulating stress responses.
BIOLOGICAL Functions of endoduplication

4. A chimera is a single organism composed of genetically distinct
cells.
In plant chimeras, however, the distinct types of tissue may originate
from the same zygote, and the difference is often due to mutation during
ordinary cell division.
Graft chimera:
These are produced by grafting part from different parents, different
cultivars or different species (which may belong to different genera).
The tissues may be partially fused together following grafting to form a
single growing organism that preserves both types of tissue in a single
shoot.
Best-known example of a graft-chimera is Laburnocytisus 'Adamii',
caused by a fusion of a Laburnum and a broom.

5. +Laburnocytisus 'Adamii' (also known as Adam's laburnum or broom
laburnum) is a horticultural curiosity; a small tree which is a graft-chimaera
between two species, a laburnum, Laburnum anagyroides, and a broom,
Chamaecytisus purpureus (syn. Cytisus purpureus), which bears some shoots
typical of the one species, some of the other, and some which are a peculiar
mixture of both "parents"

6. Chromosomal chimeras
These are chimeras in which the layers differ in their chromosome constitution.
Occasionally chimeras arise from loss or gain of individual chromosomes or
chromosome fragments owing to misdivision. More commonly cytochimeras
have simple multiple of the normal chromosome complement in the changed
layer. There are various effects on cell size and growth characteristics.
Nuclear gene-differential chimeras
These chimeras arise by spontaneous or induced mutation of a nuclear gene to
a dominant or recessive allele. As a rule one character is affected at a time in
the leaf, flower, fruit, or other parts.

7. Plastid gene-differential chimeras
These chimeras arise by spontaneous or induced mutation of a plastid gene,
followed by the sorting-out of two kinds of plastid during vegetative growth.
The majority of variegated-leaf chimeras are of this kind.
All plastid gene- and some nuclear gene-differential chimeras affect the color
within the leaves, and these are grouped together as chlorophyll chimeras, or
preferably as variegated leaf chimeras