A neuron that has only one axon but several dendrites is classified as:
a. multipolar neuron.
Explanation:
The neurons are the fundamental unit of the nervous system.
The nervous system consist of only two types of cell; neurons and neuroglia.
Neurons are specialized to respond to physical and chemical stimuli, conduct nerve impulse and release neurotransmitter , while the neuroglia supports , nourish and protect the neuron.
Most neurons have three parts: a cell body, dendrites and axon.
Neurons show a great diversity in size and shape, and are classified on the basis of structure and function.
On the Basis of structure the neurons are classified as: unipolar, bipolar and multipolar. (Multidendritic neurons are studied in <em>Drosophilla </em>and are reported to be a result of misexpressed<em> gene</em>)..
Multipolar neurons are the most common type of neurons in the brain and spinal cord and have several dendritic processes and one axon.
Bipolar neurons are found in retina of the eye, in the inner ear and in the olfactory area of the brain and are characterized by one dendrite and one axon.
Uni-polar neurons have single processes extending from the cell body which divide into two branches.
On the basis of function neurons are classified as; sensory, motor and association neurons.
Eccentricity is the ratio of the distance from the center of an ellipse to one of its foci to the distance from the center of the ellipse to one of its vertices.
a. The maternal copy of UBE3A is expressed and the paternal copy is silenced.
Explanation:
When UBE3A chromosome is in neurons, paternal allele is silent and maternal allele is expressed in process of genomic imprinting. In some cases UBE3A is expressed from both paternal and maternal chromosomes. The paternal chromosome is blue whereas maternal chromosome is magenta.