CYTOPLASMIC INHERITANCE

CYTOPLASMIC INHERITANCE
Presented by: Ankit Kumar Dubey
Title: Cytoplasmic Inheritance
School: School of Chemical and Biological Sciences
Supervisor/Teacher in charge: Mrs. Ramya M
Affiliation: REVA UNIVERSITY

Contents
Introduction
Mitochondrial or maternal inheritance
• Shell coiling in Snail(Limnaea pregra)
Plastidial or chloroplast inheritance
• Leaf variegation in Mirabilis Jalapa
Inheritance Involving Infective Particles
• Kappa particles in Paramecium
Signififcance
References
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Introduction
 Inheritance due to genes located in cytoplasm (plasmagenes).
The plasmagenes are located in DNA present in mitochondria and in
chloroplasts.
Together both the DNAs are called organelle DNA. therefore, this
type of inheritance is often referred to as organellar inheritance,
plastid inheritance or mitochondrial inheritance.
The cytoplasmic inheritance is of three types:
1) Maternal inheritance,
2) Organellar inheritance,and
3) Inheritance Involving Infectious Particles
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Maternal inheritance
In this, generally, the character of only one of the two parents
(usually female) is transmitted to the progeny.
Hence such inheritance is usually referred to as extra - nuclear or
extra-chromosomal or maternal or uniparental inheritance.
In most animals, paternal mitochondria enter the oocyte cytoplasm
after fertilization, their mtDNA is never transmitted to the offspring.
This pattern of mtDNA inheritance is well known as "maternal
inheritance."
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Shell Coiling In Snail (Limnaea pregra)
In snails (gastropods)the shell is spirally
coiled.
Snails exhibit two types of coiling of
their shell:
Shell coiled to right is dextral.
Shell coiled to left is sinistral.
The gene for dextral coiling is dominant
‘D’ and for sinistral coiling is recessive ‘d’.
Boycott and Driver(1923) showed that
the character of coiling is determined by
the gene of the mother and not by the
individual’s own gene.
5Pic.Source: www.molluscs.at/gastropoda/terrestrial/helix.html?/gastropoda/terrestrial/helix/crossing.html

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Shell coiling in the hermaphroditic snail Limnaea peregra may be right-handed
(dextral) or left-handed (sinistral).
The coiling depends on the genotype of egg donor parent, regardless of the
phenotype of that parent.
• If that parent is DD or Dd, the offspring will be dextral.
Pic.Source: www.yourarticlelibrary.com/biology/4-examples-of-extra-nuclear-inheritance-in-
eukaryotes-biology/6364/

Organellar inheritance
The true cytoplasmic inheritance is one
which involves plastids (chloroplasts) and
mitochondria.
Thus, cytoplasmic inheritance is again of
two types, viz.,
1. plastid inheritance and
2. mitochondrial inheritance.
The cytoplasmic inheritance is governed by
genes which are found in chloroplasts and
mitochondria.
The genes which govern cytoplasmic
inheritance are c alled plasma genes or
cytoplasmic genes or cytogenes or extra
nuclear genes.
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Pic.Source: Griffiths AJF, Miller JH, Suzuki DT, et al.New York” Inheritance of organelle genes and mutations”;
W. H. Freeman; 2000.

Leaf variegation in Mirabilis Jalapa
The conclusive evidence for cytoplasmic inheritance was first
presented by Carl Correns in Mirabilis jalapa (Four ‘O’ clock plant) in
1909.
He studied inheritance of leaf variegation in M. jalapa.
 Variegation refers to the presence of white or yellow spots of
variable size on the green background of leaves.
In M. jalapa, leaves may be green, white or variegated. Some
branches may have only green, only white or only variegated leaves.
Correns made crosses in all possible combinations among the flowers
produced on these three types of branches.
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Flowers on wholly green
branches produce seeds that
grow into normal plants.
Flowers on variegated branches
yield offspring of three kinds-
green, white and variegated in
variable proportions.
Flowers from branches wholly
white produce seeds that grow
into white plants that is without
chlorophyll.
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Pic Source: www.nature.com/scitable/topicpage/Non-nuclear-Genes-and-Their-Inheritance-589#

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.
There are three types of male sterility in crop plants, viz., genetic
(controlled by nuclear genes), cytoplasmic (controlled by plasma
genes) and cytoplasmic genetic (controlled by both nuclear and
plasma genes). The cytoplasmic male sterility is controlled by plasma
genes associated with mtDNA or cpDNA.
In other words, in maize cytoplasmic sterility is governed by
mitochondrial DNA. Cytoplasmic sterility is found in several other
crop plants, viz., pearl millet, Sorghum, cotton, etc.
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In certain other cases, although male sterility
is wholly controlled by cytoplasm, but a
restorer gene if present in the nucleus will
restore fertility.
 For instance, if female parent is male sterile,
then genotype (nucleus) of male parent will
determine the phenotype of F1progeny.
The male sterile female parent will have the
recessive genotype (rr) with respect to
restorer gene. If male parent is RR, F1 progeny
would be fertile (Rr).
On the other hand, if male parent is rr, the
progeny would be male sterile.
 If F1 individual (Rr)is testcrossed, 50% fertile
and 50% male sterile progeny would be
obtained
Fig: Inheritance of genetic male sterility in
plants.
Picsource:www.eplantscience.com/index/genetics/maternal_effects_and_cytoplasmic_inheritance/male_sterility_
in_plants.php

Inheritance Involving Infective
Particles
In some cases, cytoplasmic inheritance is associated with infective
particles like parasite, symbiont or viruses which are present in the
cytoplasm of an organism.
There are cases, where cytoplasmic inheritance depends on extra-
chromosomal 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.
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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 one killer and the other
sensitive.
The killer secretes a toxic substance called paramecin which kills the
sensitive.
The paramecia of killer strain contain large number of kappa
particles in their cytoplasm.
The production of kappa particles is dependent on a dominant
allele K, so that killer strains are KK or Kk and sensitive strains are
ordinarily kk.
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Fig: Results of a cross between a killer (KK) and a
sensitive (kk) strain of Paramecium, when no
cytoplasmic exchange is allowed.
Fig: Results of a cross between a killer (KK)and a
sensitive (kk) strain of Paramecium, when cytoplasmic
exchange is allowed.
Pic.source:www.biocyclopedia.com/index/genetics/maternal_effects_and_cytoplasmic_inheritance/kapp
a_particles_in_paramecium.php

Significance
1.Cytoplasmic inheritance has been useful in explaining the role of various
cytoplasmic organelles in the transmission of characters in different
organisms.
2. Studies of cytoplasmic inheritance have played key role in mapping of
chloroplast and mitochondrial genome in several species, viz., yeasts,
clamydomonas, maize, human, etc.
3. 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 desirable to utilize various CMS sources.
4. Role of mitochondria in the manifestation of heterosis is gaining increasing
importance these days.
5. Mutation of chloroplast DNA and mitochondrial DNA leads to generation of new
variants. Some of such variants are of special significance especially in ornamental
plants.
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References
www.molluscs.at/gastropoda/terrestrial/helix.html?/gastropoda/terrestrial/helix/crossing.html
www.yourarticlelibrary.com/biology/4-examples-of-extra-nuclear-inheritance-in-
eukaryotes-biology/6364/
Griffiths AJF, Miller JH, Suzuki DT, et al.New York” Inheritance of organelle genes and
mutations”; W. H. Freeman; 2000.
www.nature.com/scitable/topicpage/Non-nuclear-Genes-and-Their-Inheritance-589#
www.biocyclopedia.com/index/genetics/maternal_effects_and_cytoplasmic_inheritance/ka
ppa_particles_in_paramecium.php
Verma P.S.; Agarwal. V.K.(2005); Cell Biology, Genetics,Molecular Biology, Evolution And
Ecology; Cytoplasmic or Extra-nuclear Inheritance;221-229
Klug,W.S...,et.al;(2012);Concepts of Genetics;Extranuclear inheritance;221-235
www.eplantscience.com/index/genetics/maternal_effects_and_cytoplasmic_inheritance/m
ale_sterility_in_plants.php
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