Sujetos
Página inicial
/
Biologia
/
b) duchenne muscular dystrophy is caused by a recessive allele located on the x chromosor people experience progressive weakening and

Question

B) Duchenne Muscular Dystrophy is caused by a recessive allele located on the X chromosor people experience progressive weakening and loss of skeletal muscle . How can,two unaffected (dominant) people have a child with Duchenne MD (recessive)? Show how in the Punnett square and explain below, square show Squar

Solution

Verificación de expertos
4.3 (320 Votos)
Eduardo Mestre · Tutor por 5 anos

Resposta

To understand how two unaffected (dominant) individuals can have a child with Duchenne Muscular Dystrophy (DMD), we need to consider the inheritance pattern of the recessive allele responsible for DMD. Since DMD is caused by a recessive allele located on the X chromosome, it primarily affects males, as they have only one X chromosome. Females, having two X chromosomes, are typically carriers (heterozygous) and may not show symptoms.Let's denote the normal allele as "X^N" and the DMD allele as "X^d".### Step-by-Step Explanation:1. **Genotypes of the Parents:** - Both parents are unaffected but carriers: X^N X^d (female) and X^N Y (male).2. **Punnett Square:** - Female (X^N X^d) can produce two types of eggs: X^N and X^d. - Male (X^N Y) can produce two types of sperm: X^N and Y. | | X^N (sperm) | Y (sperm) | |-------|-------------|-----------| | **X^N (egg)** | X^N X^N | X^N Y | | **X^d (egg)** | X^N X^d | X^d Y |3. **Possible Offspring:** - X^N X^N: Female, unaffected carrier. - X^N X^d: Female, unaffected carrier. - X^N Y: Male, unaffected. - X^d Y: Male, affected with Duchenne Muscular Dystrophy.### Explanation:- In this scenario, there is a 25% chance (1 out of 4) that the offspring will be a male (X^d Y) and thus affected by Duchenne Muscular Dystrophy.- The other possibilities are: - 75% chance of having an unaffected child (either X^N X^N or X^N Y for females or males). - 25% chance of having a carrier female (X^N X^d).### Conclusion:Two unaffected carriers can have a child with Duchenne Muscular Dystrophy because each parent carries one copy of the recessive allele. When both parents are carriers, there is a 25% probability that a son will inherit the X chromosome carrying the DMD allele from both parents, resulting in the condition.