Katie has a rare neurological disease in which her neurons can receive new information and process it, but some of them just cannot pass the information along. This disease most likely affects the axon of the neurons. Since axon is the signal transmitting end of the neuron, if the fusion of the vesicles containing the neurotransmitters with the cell membrane around the synaptic cleft is hampered, then the signal transmission gets disrupted.
Answer:
homo-zygous lethal dominant
Explanation:
A homo-zygous lethal pattern is a type of inheritance where an allele is lethal in homo-zygous individuals. In normal dominance, the expected genotype ratio when F1 heterozygous individuals are crossed is 1:2:1 (i.e. 1 homo-zygous dominant: 2 heterozygous individuals and 1 homo-zygous recessive), while the phenotypic ratio is 3:1 (3 individuals expressing the dominant allele: 1 individual only expressing the recessive allele). In this case, the homo-zygous lethal allele changes the expected F2 phenotypic ratio to 2:1 (i.e., 2 heterozygous singing Beetles : 1 homo-zygous recessive non-singing Beetles), where the partially dominant allele is lethal in homo-zygous individuals.
