Case Study: Parents of a 3-year-old boy noticed that their son had a waddling gait, fell frequently and had difficulty getting up again, and was not able to run. By age five, there was progressive muscular weakness and muscle wasting, and weakness of the trunk muscles led to abnormal posture. By age 9 he was confined to a wheelchair. Contractures appeared, first in the feet, as the gastrocnemius muscles tightened.1. This hereditary X-linked recessive disease characterized by progressive muscular weakness is .2. What does dystrophy mean? Why is this term used to describe this case?

Muscular dystrophy

Explanation:

Muscular dystrophy is an inheritable genetic condition that involves mutations in genes that encodes the production of muscle proteins to build and to preserve healthy proteins. The disease is characterised by progressive weakness and loss of muscle mass.

Dystrophy is referred to as a disorder in which the a tissue or an orgasm progressively wastes away. Thé dystrophy term is used because the disease involves the gradual and progressive wasting away of the muscle which is a type of tissue causing muscular weakness allowing the child to experience these symptoms.

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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.