Stem cell transplants may someday be used to treat Parkinson's disease. Researchers are hopeful that these cells would alleviate the symptoms of Parkinson's disease by

Researchers are hopeful that these cells would alleviate the symptoms of Parkinson's disease by secreting the neurotransmitter dopamine.

Explanation:

Dopamine is a neurotransmitter released by the brain that plays a role in pain processing at various levels of the central nervous system. This includes the spinal cord, periaduectal gray matter, the thalamus, the basal ganglia, the insular cortex, and the cingulate cortex. Low dopamine levels are associated with the painful symptoms that frequently occur in Parkinson's disease. Parkinson's is generated from a neurodegenerative disorder that mainly affects dopaminergic neurons, responsible for producing and secreting dopamine within the brain. When these neurons degenerate, dopamine levels decrease and the consequences are tremor, muscle stiffness and difficulty making voluntary movements, among others.  In Parkinson's disease, there is a loss of dopaminergic neurons and a potential treatment would be that the lost neurons could somehow be replaced. One possibility is to transplant stem cells that differentiate into dopamine-producing nerve cells.

an individual’s sex (i.e., whether they are a male or female) is determined by the sex chromosomes. most people have two sex chromosomes, one that is inherited from their mother and one that is inherited from their father. typically, females have two x chromosomes (xx) and males have one x chromosome and one y chromosome (xy). conditions caused by changes (“mutations”) in genes located on the x chromosome are considered x-linked.

x-linked recessive inheritance

most x-linked conditions are recessive. this means that in a person with two x chromosomes (most females), both copies of a gene (i.e., one on each x chromosome) must have a change or mutation whereas in a person with one x chromosome (most males), only one copy of a gene must have a mutation. a female with a mutation in one copy of a gene on the x chromosome is said to be a “carrier” for an x-linked condition. a male with a mutation in a gene on the x chromosome is typically affected with the condition. because females have two copies of the x chromosome and males have only one x chromosome, x-linked recessive diseases are more common among males than females. however, x-linked recessive diseases can occur in both males and females.

for x-linked recessive disorders, an unaffected carrier mother who has a mutation in a gene on the x chromosome can transmit either the x chromosome with this mutation or a “normal” x chromosome to her children. if the father is unaffected, none of her daughters will be affected and all of her daughters will be unaffected—since they will inherit at least one normal x chromosome from their father. however, each daughter will have a 50% chance of being an unaffected carrier like her mother and a 50% chance of both x chromosomes being normal.