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Duchenne/Becker Muscular Dystrophy (DBMD)    

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Duchenne/Becker Muscular Dystrophy (DBMD)

Photos of boys  

 

About Genes and Mutations

What Are Genes?
Genes contain the instructions that tell the cells of people’s bodies how to grow and work. For example, the instructions in genes control what color a person’s eyes are and how tall a person will be. Each person gets half of his or her genes from each parent, and that is why a person tends to look like his or her parent.

Genes are stored in a chemical called deoxyribonucleic acid (DNA). DNA is a chemical chain made up of “bases”. There are four bases: A, C, T, and G. The specific order, or sequence, of these bases determines the exact information carried in each gene, like the way that a specific pattern of letters makes up the words in a sentence. For more details, click here.

 

What Are Mutations?
A mutation is any change in a gene that makes it different from the usual copy (the copy that most people have). If the change causes a difference in the way that the gene works, the person with the mutation could have a particular condition (such as muscular dystrophy) that runs in the family. Different changes run in families in different ways. For more details on mutations, click here.

 

X-Linked Conditions

X-linked conditions usually affect only males. A mutation causing a condition can be passed in the family through female carriers who do not have the condition. However, each son of a female carrier has a 50% chance of inheriting the mutation and, therefore, of having the condition.

“X-linked” genes are genes that are found on the X chromosome. “Recessive” means that a person can have the condition only if he or she does not have at least one usual copy of the gene.

A female has two X chromosomes and, therefore, two copies of each X-linked gene. A woman who has one usual copy and one copy with a recessive mutation is called a carrier. She does not have the condition, but can pass the copy with the recessive mutation on to her children.

A male has only one copy of the X chromosome, which he has gotten from his mother. If the copy that he gets is the copy with the recessive mutation, he will have the condition because he does not have a usual copy of the gene. If he gets his mother’s X chromosome that has the usual copy of the gene, he will not have the condition. Therefore, a son of a carrier mother has a 50% chance of having the condition. A male who has the condition passes his X chromosome to each of his daughters, so each daughter will be a carrier. A male with the condition passes his Y chromosome to each of his sons, so none of his sons will have the condition or be carriers (unless the mother is also a carrier).

X-link diagram

Topic Contents

DBMD Home Page

Causes of DBMD

About Genes & Mutations

EG's Story

References

Resources

What is CDC doing about DBMD?
 


August 2004 Project Updates [PDF]


Newborn Screening for DMD Workgroup Report [PDF]

Contact Information
 

Duchenne/Becker Muscular Dystrophy Program
Division of Human Development and Disability
National Center on Birth Defects and Developmental Disabilities
Centers for Disease Control and Prevention
Mailstop E-88
1600 Clifton Road NE
Atlanta, Georgia 30333
Email:  dmd@cdc.gov
 

 

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National Center on Birth Defects and Developmental Disabilities

The National Center on Birth Defects and Developmental Disabilities (NCBDDD) promotes the health of babies, children, and adults, and enhances the potential for full, productive living.  Our work includes identifying the causes of birth defects and developmental disabilities, helping children to develop and reach their full potential, and promoting health and well-being among people of all ages with disabilities.