Cytoplasmic inheritance

Cytoplasmic Inheritance AGB121 Dept. Of AGB Veterinary College, Hebbal, Bangalore

Definition • Factors inherited from a source other than Nucleus Also called  Extra nuclear inheritance  Extra chromosomal inheritance  Maternal Inheritance

Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Types of Cytoplasmic Inheritance 1. Plastid Inheritance 2. Male sterility in plants 3. Streptomycin resistance 4. Enzyme controlled

6. CO2 sensitivity 7. Coiling in snails 8. Eye colour in beach hoppers 9. Cancer producing milk virus in mice

5. Killer particles

Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Plastid Inheritance (Carl Correns 1908)

Inheritance of Chloroplastids only through maternal egg

Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Plastid Inheritance

Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Male sterility in Plants Rhodes M M

Male sterility genes are inherited in cytoplasm of the female gametes.

Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Coiling in Snails

Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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CO2 sensitivity in Drosophila L'Heritier and Teisser(1958) True breeding strain of Drosophila which was sensitive to Co2

Sensitive flies become unconscious when exposed to CO2 and are paralysed

When reciprocal crosses were made between CO2 sensitive and normal strains, it could be shown that the trait was inherited only from female parent.

This sensitivity can be attributed to a virus like particle Dr R Jayashree, Asst. Prof(AGB), Veterinary 8 College, Bangalore called sigma found in cytoplasm of the cells of a sensitive fly

Killer Particle Paramaecium Certain Killer strains posses Kappa particles which synthesize paramecin

Dominant allele K is required for production of – Kappa Particles in cytoplasm KK or Kk are Killer strains if Kappa particles are present in the cytoplasm Without kappa particles they become sensitive strains Sensitive strains are kkDr Rnormally Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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No Cytoplasmic Exchange

Cytoplasmic Exchange

Killer strain is formed when Sensitive strain KK & kk there cytoplasmic exchange Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Milk factors in Mice 1936, by Dr. John Joseph Bittner

Cancerous agent, or "milk factor", could be transmitted by cancerous mothers to young mice from a virus in their mother's milk.

If the mice were fed milk from foster mother they did’nt get cancer.

Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Phenocopy A phenocopy is an individual whose phenotype (generally referring to a single trait), under a particular environmental condition, is identical to the one of another individual whose phenotype is determined by the genotype.

The environmental agents producing phenocopies includes temperature, shock, radiation, and various chemical compounds

Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Phenocopy In Drosophila melanogaster T.H. Morgan in 1910 The. normal body colour is brownish-gray with black margins Larva of normal flies were fed with silver salts, develop into yellow bodied flies irrespective of their genotype

The yellow bodied flies which are genetically brown is a variant of the original yellow bodied fly.

Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Phenocopy in Himalayan Rabbits Himalayan rabbits are white in colour with black tail, nose, and ears when raised in moderate temperatures.

However when raised in colder climates, they become phenotypically distinguishable.

They show black colouration of their coats, resembling the genetically black rabbits.

Hence this Himalayan rabbit is a phenocopy of the genetically black rabbit Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Freemartin

• Infertile female when born as a co-twin to a male calf • The calf will have masculanized behaviour and non functioning ovaries

Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Karyotype of freemartin It is Chimeric with the sample of cells showing XX/XY chromosomes. and pigs Externally, the animal appears female, but various aspects of female reproductive development are altered due to acquisition of anti-M端llerian hormone from the male twin.

It also occurs occasionally in other mammals including sheep, goats and pigs Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Freemartinism

The animal originates as a female (XX), but acquires the male (XY) component in utero by exchange of some cellular material from a male twin, via vascular connections between placentas Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Lethal Genes

Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Lethal Genes • Genes with regularly fatal effects are called lethal genes • Some lethal genes are completely recessive and produce no effect in heterozygous state • Some maybe semi lethal or sub-lethal in heterozygous state such genes modify the classical Mendelian Ratio • Some lethals may be dominant Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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LETHAL GENE • A lethal gene causes death of individual in the appropriate genotype before they reach adulthood.

• 1904 French geneticist Lucien Cuenot, discovered a recessive lethal affecting coat colour in mice.

Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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LETHAL GENE • Yellow colour is dominant • Crossing 2 yellow mice the ratio was 2:1 ratio • Crossing yellow with recessive wild type (grey) it was found that all were yellow.

• Concluded all yellow mice were heterozygotes.

Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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LETHAL GENE • Later it was suggested that homozygosity for yellow is lethal, and that these individuals died in utero, a fact observed by histological studies.

Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Lethal Alleles Example: Manx cat ML = tailless, lethal in homozygote m = tail

The allele interferes with normal spinal development, in heterozygous cats this results in lack of a tail.

Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Manx Cat

Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Lethal Genes – Creeper Chickens

Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Lethal Genes in Mexican hairless dogs

– Hh – Hh – HH

hairy hairless lethal

normal trait one mutation present two mutations = lethal

Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Dexter and Kerry

It is sub-lethal The heterozygous condition results in short legged Dexter Dr R Jayashree, Asst. Prof(AGB), Veterinary cattle College, Bangalore

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Bull dog calves

Caused by single recessive gene in homozygous condition Calves are aborted at 6-8 months Abnormal head with short face and short upper jaw, short legs and cleft palate Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Other conditions in Cattle • Parrot beak- In homzygous recessive state • Amputated- Condition where the head legs and lower jaw are missing • Short spine- Compacted vertebrae ,the calf dies at or before birth

Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Lethal conditions in Human • Sickel cell Anaemia • Cooley’s anaemia or Thalassemia major • Juvenile idiocy- deterioration of mental and physical powers caused by recessive lethal genes • Infantile- Death of the child at 2-3 years of age • Blindness- Colour and night blindness caused by recessive genes in homozygous recessive state • Epidermolysis- Blisters on the skin- Homozygous recessive genes Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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PLEIOTROPY

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- Impact of a single gene on more than one characteristic • - Sickle-cell disease – - Most common inherited illness among black people – - RBCs are sickle-shaped – Can cause many problems

RBCs: Sickle-cell disease

Normal RBCs

Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Sickle Cell Anemia Under conditions of low oxygen tension, hemoglobin S will precipitate, causing cells to sickle

Mutations in same amino acid

Some individuals die in childhood; Some individuals have mild symptoms HbA: V – H – L – T- P – G –G HbS: V – H – L – T- P – V–G Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Achondroplasia • The most common form of dwarfism, with a normal length body trunk but shortened limbs.

Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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