the cytoplasmic inheritance is in which cytoplasm contain self replicating hereditary material of cytoplasm formed of DNA and this DNA govern many specific characters in plants and animals.

1. CYTOPLASMIC INHERITANCE
OR
EXTRACHROMOSOMAL
INHERITANCE

2. INTRODUCTION
• In 1950 Dr. Sangers and his colleagues suggested the possible role of cytoplasm in
certain cases of inheritance .
Example – in Chlamydomonas inheritance of certain characters is controlled by the
non-chromosomal genes.
• The cytoplasm in such cases contains self-perpetuating hereditary particles
formed of DNA. These may be mitochondria, plastids or foreign organisms etc.
• The total self-duplicating hereditary material of cytoplasm is called plasmon and
the cytoplasm units of inheritance are described as plasmagenes.
• Plasmagenes are located in DNA present in mitochondria and in chloroplast.

3. Total hereditary material
Plasmon( all hereditary
material in
cytoplasm)extra
chromosomal
Plastogenes ( in plastid)
Kinetogenes (in
kinetosome)
Chondriogene(in
mitochondria)
Centriogenes(centrioles)
Genome(all hereditary
material in nucleus)
genes
Types of hereditary material in living
organisms

4. The crosses exhibiting following types of results
may suggest extrachromosomal inheritance:-
Differences in
reciprocal cross
results
Maternal
influence
Infection like
transmission
Indifference to
nuclear
substitution
Inconsistent with
the Segregation
and non Mendelian
segregation

5. Criteria for cytoplasmic inheritance
The cases of cytoplasmic inheritance are found to exhibit maternal influence.
There is very little cytoplasm is contained in sperm and most of the
cytoplasm is contributed to the zygote by ovum or egg.
Hence, if there are hereditary units in the cytoplasm, these will be
transmitted to the offspring through the egg.
The offspring, therefore, will exhibit maternal influence.

6. Three types of cytoplasmic inheritance
Maternal inheritance
Organellar inheritance
Inheritance involving infectious
particles

7. Examples of Maternal inheritance
1. Maternal influence on Shell Coiling in Snail Limnaea:
• Snail exhibit two types of coiling of their shell:
Dextral coiling
• The shells coiled towards right.
Dominant (D)
Sinistral coiling
• Those coiled towards left.
RECESSIVE (d)

8. The experiment of Boycott, Diver and Gastric and explanation given by Sturtevant
indicate that the character of coiling is determined by the gene of the mother and
not by the individual's own gene.
If a dextral female is crossed with
sinistral male, all the F1 Snails possess
dextral shell. Surprisingly even in F2
also all the offspring possess dextral
shell irrespective of the fact that a
few of them possessed recessive
genes and were supposed to develop
sinistral coiling.
In a reciprocal cross between sinistral
female and dextral male, and the F1
offspring which according to their
genotype were supposed to be
dextral, were found to develop
sinistral shell coiling and in
F2 generation all the offspring
developed dextral coiling.

9. Abnormal observations of reciprocal crosses
• Some of the snails which are homozygous for sinistral coiling have
dextral coiling similar to the mother.
• Some of the snails which have gene for dextral character display
sinsitral coiling like the mother.
 It clearly indicates that maternal genotype through her egg
cytoplasm dictates the shell coiling of the offspring.

11. Inheritance involving infective
particles
 In some cases, cytoplasmic inheritance is associated
with infective particles, like parasite, symbiotic or
viruses which are present in the cytoplasmic of an
organism.
 There are cases, where cytoplasmic inheritance depends
on extrachromosomal particles which are not essential
for cell function and therefore may be present or absent.
 Such, dispensable particles are not only inherited but are
also infective, since they can be introduced into new
hosts without the need of actual process of reproduction.

12. Kappa particles in Paramecium
• Sonneborn(1943) described the inheritance of some cytoplasmic
particles known as kappa and their relation to nuclear gene in
Paramecium.
• There are two strains of Paramecium
• The killer secretes a toxic substance
Called paramecin which kills the sensitive.
• The paramecin of killer strain contain large number of kappa
particles in their cytoplasm.
• The product of kappa particles is dependent on a dominant allele K,
that killer strains are KK or Kk and sensitive strains are ordinarily
kk.
Killer sensitive

15. Breast tumour In Mice
• The mammary cancer in mice has been found to be
maternally transmitted.
• Studied by Bitiner
• When females mice crossed with normal males without
cancer susceptibility almost 90% of the
offspring developed breast cancer.
• When males from this tumour susceptible strain were
mated to normal females all the offspring were normal.
• These results are suggestive of cytoplasmic inheritance.

17. Organellar
inheritance
• The true cytoplasmic inheritance is one
which involves plastids (chloroplast) and
mitochindria.
• Thus cytoplasmic inheritance is again of two
types :
1. Plastid inheritance
2 Mitochondria inheritance
• The cytoplasmic inheritance is governed by
genes which are found in chloroplast and
mitochondria.
• The genes which govern cytoplasmic
inheritance are callled palsma genes or
cytoplasmic genes or cytogene or
extranuclear genes.

18. Leaf varigation in Mirabilis
jalapa
• The conclusive evidence for cytoplasmic inheritance was first
presented by Carl Correns in Mirabilis jalapa (four 'o' clock palnt) in
1909.
• He studied inheritance of leaf varigation in M. jalapa.
• Varigation refers to the presence of white or yellow spote of
variable size on the green background of leaves.
• In M. jalapa, leaves may be green, white or varigated. Some
branches mat have only green, only white and only varigated
leaves.
• Correns made crosses in all possible combinations among the
flowers produced on these three types of branches.

19. • Flowers on wholly green branches produce
seeds that grow into normal plants.
• Flowers on varigated branches yield offspring of three kinds
green, white and variegatedin variable proportions.
• Flowers from branches wholly white produces seeds
that grow into white plants that is without chlorophyll.

22. Cytoplasmic
male sterility
The inheritance of some characters is governed by
mitochondrial DNA. The examples of mitochondrial inheritance
include cytoplasmic male sterility in plants, pokyness in
Neurospora, petite in yeast etc.
The cytoplasmic male sterility is controlled by plasma genes
associated with mtDNA ir cpDNA.
In other words, in maize cytoplasmic sterility is governed by
mitochondrial DNA. Cytoplasmic sterility is found in several
other crop plants, pearl millet, Sorghum, cotton, etc.
In certain other cases, although male sterility is
wholly controlled by cytoplasm, but a restorer gene if present in
the nucleus will restore fertility.

23. • For instance , if female parent is male sterile,
then genotype (nucleus) of male parent will
determine the phenotype of F1 progeny.
• The male sterile female parent will have the
recessive genotype (rr) with respect to restore
gene. If male parent is RR, F1 progeny would be
fertile (Rr).
• On the other hand , if male parents is rr , the
progeny would be male sterile.
• If F1 individual (Rr) is testcrossed , 50% fertile
and 50% male sterile progeny would be
obtained.

24. Inheritance of genetic
Male sterility in plants
25% 50% 25%

25. Significance
• Cytoplasmic inheritance has been useful in explaining the role of various
cytoplasmic organelles in the transmission of characters in different organisms.
• Studies of cytoplasmic inheritance have played key role in mapping of
chloroplast and mitochondrial genome in several species example yeast,
Chlamydomonas, maize, human etc.
• The CMS cytoplasm can be easily transferred to various agronomic bases for
their use in the development of superior hybrids. Since CMS based hybrids
have danger of uniformity, it is describe to utilize various CMS sources.
• Role of mitochondria in the manifestation of heterosis is gaining
increasing importance these days.

26. THANKS