Organelle Genetics

Organelle DNA heredity: Extranuclear, uniparental, female contributes bulk of cytoplasm to progeny, paternal and biparental exceptions, no segregation ratios.

Chloroplast DNA heredity: Strict maternal inheritance seen for zygotes where egg cell is from non-variegated branch, egg cells from variegated branch may have cpDNA with mutation, or WT cpDNA, or a mixture (cytohets).

Cytohets: a mixture of wt and mt cpDNA.

heteroplasmy: both WT and MT cpDNA containing cells and tissues.

Cytoplasmic segregation: following mitosis progeny with mixture of chloroplasts segregate by stochastic partitioning, random cpDNA segregation.

The severity of Mitochondrial disease: associated with the proportion of mutated mtDNA inherited.

Leber Hereditary optic neuropathy: LHON, sudden bilateral blindness.

Myoclonic epilepsy and ragged red fibre: MERRF disease, lack of muscle coordination, deafness, dementia.

Division Chloroplasts: Chloroplasts come from pre-existing chloroplasts.

ftsZ: filamentous temperature sensitive protein, bacterial cell division protein, forms a Z ring inside chloroplast lining inner membrane surface.

ARC5: dynamin-related protein, forms a ring outside the chloroplast, twists to pinch membrane.

Division mitochondria: dynamin like proteins on both inner and outer membranes, fission type proteins act at outer membrane, interact with cytoskeletal components during cytokinesis.

Mitochondrial replication: Heavy strand forms in displacement loop, loop expands light strand starts replication starts to look like a D instea of an O.

RNA editing in Mitochondria: changes the nucleotide sequence of transcripts, Creation of an ORF, creation of translation start and stop codons, changes the AA sequence relative to that predicted by the DNA.

cytoplasmic male sterility: CMS controlled by plant mitochondrial genomes, inability to produce functional pollen, plants phenotypically normal other than male reproductive properties.

CMS genes: 14 mt genes, mainly GOF, chimeric genes (recombination b/ mtGenomes) genes encoding ATP synthase and Cytochrome Oxidase.

CMS Phenotypes: altered floral morphology (absence of stamen, anthers, pollen grains), Homeotic CMS phenotypes, Degenerative CMS phenotypes (anther and pollen degradation).

Fertility restoration genes: repress or neutralize genes associated with CMS, nuclear-encoded, mostly members of the pentatricopeptide repeat (PPR) protein family.

Chloroplast advantages: high-level production of transgene product, high precise integration of transgenes due to HR, transgene stacking in operons, no epigenetic effects.

Chloroplast applications: herbicide and pathogen resistance, biopharmaceuticals, metabolic pathway modification.

Chloroplast transformation: reverse genetics, Gene replacement, biotechnology and test of expression elements.

Biolistic mediated transformation: introduction of foreign DNA across two membranes of the chloroplast envelope, selection on medium containing the antibiotic that corresponds to the resistance marker gene in transformation vector.

cp transformation Pathogen resistance: cry genes encode crystal toxin proteins active against different insect species.