Organism that is able to utilize carbon dioxide as a carbon source autozygosity homozygosity in which the two alleles are identical by descent(ie they are copies of an ancestral gene) auxotroph An organism with specific nutritional requirements auxotrophic mutant A mutant strain of microorganism that will proliferate only when the medium is supplemented with some specific substance not required by wild-tvpe organisms axoneme a bundle of microtubules and other proteins forming the core of each cilium or flagellum B form dnA A right-handed double-helical conformation of DNA normally seen in solution described by Watson and Crick. A second DNA conformation(A form) is seen in unhydrated DNA fibres or crystals of oligonucleotide bacillus A rod-shaped bacterium back mutation The process that causes reversion. A change in a nucleotide pair in a mutant gene that restores the original sequence and hence the original phenotype backcross The cross of an individual with one of its parents or an organism with the same genotype as a parent. bacterial lawn A continuous cover of bacteria on the surface of a growth medium bacteriophage(phage) a virus that infects bacteria balanced lethal system An arrangement of recessive lethal alleles that maintains a heterozygous chromosome combination. homozygotes for any lethal-bearing chromosome perish balanced polymorphism Stable genetic polymorphism maintained by natural selectionOrganism that is able to utilize carbon dioxide as a carbon source. autozygosity homozygosity in which the two alleles are identical by descent (ie they are copies of an ancestral gene) . auxotroph An organism with specific nutritional requirements. auxotrophic mutant A mutant strain of microorganism that will proliferate only when the medium is supplemented with some specific substance not required by wild-type organisms. axoneme A bundle of microtubules and other proteins forming the core of each cilium or flagellum. B form DNA A right-handed double-helical conformation of DNA normally seen in solution described by Watson and Crick. A second DNA conformation (A form) is seen in unhydrated DNA (fibres or crystals of oligonucleotides). bacillus A rod-shaped bacterium. back mutation The process that causes reversion. A change in a nucleotide pair in a mutant gene that restores the original sequence and hence the original phenotype. backcross The cross of an individual with one of its parents or an organism with the same genotype as a parent. bacterial lawn A continuous cover of bacteria on the surface of a growth medium. bacteriophage(phage) A virusthat infects bacteria. balanced lethal system An arrangement of recessive lethal alleles that maintains a heterozygous chromosome combination. homozygotes for any lethal-bearing chromosome perish. balanced polymorphism Stable genetic polymorphism maintained by natural selection