extrachromosomal inheritance Flashcards
How was extranuclear influence on phenotype discovered
discovery of DNA in mitochondria and chloroplasts
Describe extranuclear inheritance
transmission of genetic info to offspring through cytoplasm not nucleus
What is organelle heredity
dna contained in mitochondria or chloroplasts determines certain phenotypic characteristics of offspring
What is infectious heredity
results from symbiotic or parasitic association with microorganism
inherited phenotype affected by microbe in host’s cytoplasm
What is the maternal effect on phenotype
Variation of extranuclear inheritance, nuclear gene products stored in egg, then transmitted through ooplasm to offspring
what is organelle heredity
involves DNA in chloroplast or mitochondria
Describe endosymbiotic theory
mitocondria and chloroplasts arose independently 2 billion years ago from free living bacteria
bacteria were engulfed by larger eukaryotic cells
eukaryotic cells gained oxidative respiration and photosynthesis
What is mtdna and cpdna
mtdna exists in eukaryotes as double stranded circular dna, smaller than dna in chloroplasts
cpdna - gene encodes products involved in photosynthesis and translation
Why is mtdna susceptible to mutation?
no structural protection from histones, dna repair mechanism limited, high concentration of toxic ROS
What is heteroplasmy
variation in genetic content of organelles causing adult cells to have variable mixture of normal and abnormal organelles
Mutated organelles diluted out by many mitochondria that lack mutation
What are the criteria for human disorders to be attributed to mtdna
inheritance must exhibit maternal inheritance pattern, disorder must reflect deficiency in bioenergetic function of organelle
Must have mutation in one or more mitochondrial gene
What is MERRF?
lack of muscular coordination, pattern of inheritance consistent with maternal coordination
what is mitochondrial replacement therapy
helps prevent mtdna disorders by using DNA from three people
