Chapter 7- Extranuclear Inheritance

[NOTE: You are only responsible for the material covered below
which appears on pages 187-194]

I. Mutations that violate Mendel's 1st rule
	A. due to extranuclear inheritance
		1. phenotype not controlled by genes on chromosomes in 
		 nucleus
II. Maternal effects
	A. individual's phenotype controlled by mother's genotype
		1. eggs contain gene products needed for proper
		 development of zygote
			a. these cytoplasmic components are made by the 
			 female when she produces the eggs
				i. before fertilization
				ii. mutation in the mother's cytoplasmic genes 
				 will affect phenotype in the zygote
	B. Example: coiling in freshwater snail shells Limnaea peregra
		1. see Figure 7.1
		2. coils can be right-handed (dextral) or 
		 left-handed (sinistral)
		3. controlled by single gene;  two alleles
			a. D- = dextral
			b. dd = sinistral
		4. DD mothers produce only right-coiled snails
		5. dd mothers produce only left-coiled snails
	C. maternal effects last for only one generation
	D. maternal effect genes control early stages of embryonic 
	 development
		1. studying mutants in these genes helps us understand 
		 the genetics of development
III. Cytoplasmic organellar genes
	A. some cytoplasmic organelles have chromosomes
		1. mitochondrial & chloroplasts	
			a. single circular chromosome
				i. present in several copies per organelle
		2. believed to have once been independent bacteria
		3. both involved in energy production and storage
	B. reproductive cycles are coordinated with cells
	C. mutations in cpDNA & mtDNA show maternal inheritance
		1. paternal contribution is eliminated
		2. similar to the way family names are inherited from 
		 father to child in northern european countries

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