Chloroplast and Mitochondria Evolution

In each eukaryote, how many genomes does it have?
Multiple, nuclear DNA and organellar DNA (mitochondria have mt, chloroplast have cp)
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How are the genomes inherited?
Independently (with a different rate & way of evolving)
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Mitochondrial genome
Circular DNA molecule, each mitochondrion contains about 40-150 copies, each cell contains multiple mitochondria
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Plastid genome (cp)
Plastome is a circular DNA molecule, each plastid (chloroplast) contains up to 1000 copies and each cell has multiple plastids
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What is nuclear inheritance?
Mendelian inheritance- 1/2 genes from mother, 1/2 from father (bi-parental inheritance)
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What is extra-nuclear/ cytoplasmic inheritance?
Where something is inherited from just 1 parent (uniparental inheritance)
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How are Cp and Mt inherited?
Maternally inherited (not always though)
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What are the exceptions to the maternal inheritance?
Gymnosperm (Cp paternal), Conifer (Mt paternal), Sequoia sempervirens (Cp and Mt paternal)
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What is leaf variegation?
Where leaves have areas of white due to mutant chloroplasts that lack chlorophyll, the mutation is passed onto the germ cells in the female seed plant and the offspring then inherit that mutation
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What is hetroplasmy?
The presence of 2 or more genetically different types of the same organelle in a single organism
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What is the cause of hetroplasmy?
Random drift (intracellular random drift, random partitioning and random replication)
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What is the endosymbiosis theory?
Mitochondria and chloroplast were separate cells, engulfed by larger cells and symbiotic relationship established, the smaller cells evolved into organelles
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What evidence is there to support the endosymbiosis theory?
Mt same size as bacteria, own circular DNA, functionally related genes close together, RNA components of ribosomes similar in cp and cyanobacteria, gene DNA sequences with high similarity, double membranes
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What happened after symbiosis?
Nutritional exchange, transfer of genes to nucleus and genes eliminated
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What is the flow of genetic material in photosynthetic eukaryotes?
Plastome to endosymbiont nuclear genome, plastome to nuclear genome of host cell, plastid and endosymbiont nuclear genomes to host nuclear genome- So nuclear genome of host cell is a mosaic of cyanobacterial, nucleomorph and host's DNA)
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What are the 2 main theories on the origin of eukaryotes
1) Eukaryote host (nucleus derived before mitochondrial endosymbiosis) 2) Prokaryote host (mitochondria acquired before eukaryotic-specific features arose)
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What are the negatives of cytoplasmic DNA?
Limited number of genes in each (37-100) Many proteins active in mt or cp are encoded by nuclear genes (however many proteins consist of a mt/cp coded unit and a nuclear coded unit)
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Why are there differences in rate of evolution between mt and cp DNA?
Different origin, low consistency of DNA replication, absence of repair and inefficient repair, high conc of mutagens resulting from the metabolic functions performed by mt
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Card 2


How are the genomes inherited?


Independently (with a different rate & way of evolving)

Card 3


Mitochondrial genome


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Card 4


Plastid genome (cp)


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Card 5


What is nuclear inheritance?


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