Vitamin D-resistant Rickets Is A Disorder Inherited As A Sex-linked, Dominant Trait. Which Of The Following Describes The Probability Of A Male Offspring Being Affected If His Mother Has A Heterozygous Genotype For The Disorder?A. 0%B. 25%C. 50%D. 100%

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Introduction

Vitamin D-resistant rickets is a rare genetic disorder that affects the development of bones in children. It is caused by a mutation in the gene that codes for the vitamin D receptor, leading to impaired bone mineralization. This disorder is inherited in an X-linked dominant pattern, meaning that a single copy of the mutated gene is enough to cause the condition. In this article, we will explore the genetic basis of vitamin D-resistant rickets and discuss the probability of a male offspring being affected if his mother has a heterozygous genotype for the disorder.

Genetics of Vitamin D-Resistant Rickets

Vitamin D-resistant rickets is caused by a mutation in the gene that codes for the vitamin D receptor (VDR). This gene is located on the X chromosome, which is one of the two sex chromosomes in humans. The X chromosome carries many genes that are essential for various bodily functions, including bone development. In the case of vitamin D-resistant rickets, the mutated VDR gene leads to impaired bone mineralization, resulting in the characteristic symptoms of the disorder.

Inheritance Pattern

The inheritance pattern of vitamin D-resistant rickets is X-linked dominant. This means that a single copy of the mutated VDR gene is enough to cause the condition. Females have two X chromosomes, one inherited from each parent, while males have one X and one Y chromosome. In females, the presence of one normal VDR gene can compensate for the presence of one mutated VDR gene, reducing the risk of developing the disorder. However, in males, who have only one X chromosome, the presence of the mutated VDR gene is enough to cause the condition.

Probability of Male Offspring Being Affected

Now, let's consider the scenario where a male offspring inherits the mutated VDR gene from his mother, who has a heterozygous genotype for the disorder. A heterozygous genotype means that the mother has one normal VDR gene and one mutated VDR gene. Since the mutated VDR gene is located on the X chromosome, the mother has a 50% chance of passing the mutated gene to each of her offspring.

Calculating the Probability

To calculate the probability of the male offspring being affected, we need to consider the following:

  • The mother has a heterozygous genotype (one normal VDR gene and one mutated VDR gene).
  • The mutated VDR gene is located on the X chromosome.
  • The male offspring inherits the X chromosome from his mother.

Since the mother has a 50% chance of passing the mutated VDR gene to each of her offspring, the male offspring has a 50% chance of inheriting the mutated gene. If the male offspring inherits the mutated gene, he will be affected by the disorder.

Conclusion

In conclusion, if a male offspring inherits the mutated VDR gene from his mother, who has a heterozygous genotype for the disorder, the probability of him being affected is 50%. This is because the mutated VDR gene is located on the X chromosome, and the mother has a 50% chance of passing the mutated gene to each of her offspring.

References

  • [1] "Vitamin D-Resistant Rickets." Genetics Home Reference, U.S. National Library of Medicine, 2022.
  • [2] "X-Linked Dominant Inheritance." Genetics Home Reference, U.S. National Library of Medicine, 2022.
  • [3] "Vitamin D Receptor." National Center for Biotechnology Information, U.S. National Library of Medicine, 2022.

Frequently Asked Questions

  • Q: What is vitamin D-resistant rickets? A: Vitamin D-resistant rickets is a rare genetic disorder that affects the development of bones in children.
  • Q: What is the inheritance pattern of vitamin D-resistant rickets? A: The inheritance pattern of vitamin D-resistant rickets is X-linked dominant.
  • Q: What is the probability of a male offspring being affected if his mother has a heterozygous genotype for the disorder? A: The probability of a male offspring being affected is 50%.

Glossary

  • Heterozygous genotype: A genotype that has two different alleles (forms) of a gene.
  • X-linked dominant: A pattern of inheritance where a single copy of the mutated gene is enough to cause the condition.
  • Vitamin D receptor: A protein that plays a crucial role in bone mineralization.
  • X chromosome: One of the two sex chromosomes in humans, which carries many genes that are essential for various bodily functions.
    Vitamin D-Resistant Rickets: A Q&A Guide =============================================

Introduction

Vitamin D-resistant rickets is a rare genetic disorder that affects the development of bones in children. It is caused by a mutation in the gene that codes for the vitamin D receptor, leading to impaired bone mineralization. In this article, we will answer some frequently asked questions about vitamin D-resistant rickets, its inheritance pattern, and the probability of a male offspring being affected.

Q&A

Q: What is vitamin D-resistant rickets?

A: Vitamin D-resistant rickets is a rare genetic disorder that affects the development of bones in children. It is caused by a mutation in the gene that codes for the vitamin D receptor, leading to impaired bone mineralization.

Q: What are the symptoms of vitamin D-resistant rickets?

A: The symptoms of vitamin D-resistant rickets include:

  • Softening of the bones (osteomalacia)
  • Deformities of the bones (bowlegs, knock knees)
  • Delayed growth and development
  • Muscle weakness
  • Bone pain

Q: What is the inheritance pattern of vitamin D-resistant rickets?

A: The inheritance pattern of vitamin D-resistant rickets is X-linked dominant. This means that a single copy of the mutated gene is enough to cause the condition.

Q: What is the probability of a male offspring being affected if his mother has a heterozygous genotype for the disorder?

A: The probability of a male offspring being affected is 50%. This is because the mutated gene is located on the X chromosome, and the mother has a 50% chance of passing the mutated gene to each of her offspring.

Q: Can females be affected by vitamin D-resistant rickets?

A: Yes, females can be affected by vitamin D-resistant rickets. However, the presence of one normal VDR gene can compensate for the presence of one mutated VDR gene, reducing the risk of developing the disorder.

Q: What is the treatment for vitamin D-resistant rickets?

A: The treatment for vitamin D-resistant rickets typically involves a combination of medications, including:

  • Vitamin D analogs
  • Calcitriol
  • Phosphate supplements
  • Calcium supplements

Q: Can vitamin D-resistant rickets be prevented?

A: While there is no guaranteed way to prevent vitamin D-resistant rickets, genetic counseling can help families understand the risk of passing the disorder to their offspring.

Q: What is the prognosis for children with vitamin D-resistant rickets?

A: The prognosis for children with vitamin D-resistant rickets varies depending on the severity of the disorder and the effectiveness of treatment. With proper treatment, many children with vitamin D-resistant rickets can lead normal lives.

Glossary

  • Heterozygous genotype: A genotype that has two different alleles (forms) of a gene.
  • X-linked dominant: A pattern of inheritance where a single copy of the mutated gene is enough to cause the condition.
  • Vitamin D receptor: A protein that plays a crucial role in bone mineralization.
  • X chromosome: One of the two sex chromosomes in humans, which carries many genes that are essential for various bodily functions.

References

  • [1] "Vitamin D-Resistant Rickets." Genetics Home Reference, U.S. National Library of Medicine, 2022.
  • [2] "X-Linked Dominant Inheritance." Genetics Home Reference, U.S. National Library of Medicine, 2022.
  • [3] "Vitamin D Receptor." National Center for Biotechnology Information, U.S. National Library of Medicine, 2022.

Frequently Asked Questions

  • Q: What is vitamin D-resistant rickets? A: Vitamin D-resistant rickets is a rare genetic disorder that affects the development of bones in children.
  • Q: What is the inheritance pattern of vitamin D-resistant rickets? A: The inheritance pattern of vitamin D-resistant rickets is X-linked dominant.
  • Q: What is the probability of a male offspring being affected if his mother has a heterozygous genotype for the disorder? A: The probability of a male offspring being affected is 50%.

Related Articles

  • "Understanding Vitamin D-Resistant Rickets: A Genetic Perspective"
  • "Genetics of Vitamin D-Resistant Rickets"
  • "Inheritance Pattern of Vitamin D-Resistant Rickets"

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