I. Retinitis pigmentosa
II. Colour blindness
III. Cystic fibrosis
IV. Duchenne muscular dystrophy
Select the correct answer using the code given below:
Understanding Recessive Sex-Linked Traits
This question asks us to identify which of the listed conditions are transmitted as recessive, sex-linked traits. A recessive, sex-linked trait is a characteristic caused by a gene located on the X chromosome, which requires two copies of the mutated allele (one on each X chromosome) to be expressed in females, and only one copy in males (since they possess only one X chromosome).
Analysis of Conditions
Let's examine each condition mentioned:
- I. Retinitis pigmentosa: While Retinitis pigmentosa encompasses various genetic forms, several types are known to be inherited in an X-linked recessive pattern. This means they fit the criteria of being recessive and sex-linked.
- II. Colour blindness: The most common forms of colour blindness, particularly red-green colour blindness, are classic examples of X-linked recessive traits.
- III. Cystic fibrosis: Cystic fibrosis is a well-known genetic disorder, but it is inherited in an autosomal recessive manner. This means the gene responsible is located on an autosome (a non-sex chromosome), not the X chromosome. Therefore, it is not a sex-linked trait.
- IV. Duchenne muscular dystrophy: Duchenne muscular dystrophy (DMD) is another prominent example of an X-linked recessive disorder. It primarily affects males.
Identifying Correct Combinations
Based on the analysis:
- Retinitis pigmentosa (some forms) is X-linked recessive.
- Colour blindness (common forms) is X-linked recessive.
- Cystic fibrosis is autosomal recessive.
- Duchenne muscular dystrophy is X-linked recessive.
Therefore, the conditions that are transmitted as recessive, sex-linked traits from the given list are Retinitis pigmentosa (I), Colour blindness (II), and Duchenne muscular dystrophy (IV).
Conclusion
The correct combination representing recessive, sex-linked traits is I, II, and IV.
Important Questions from Miscellaneous
A 42-year old man with history of alcohol dependency presents with progressive abdominal distension. Abdominal examination reveals a
shifting dullness. Which one of the following is the most appropriate drug to relieve this abdominal distension?Which one of the following is the investigation of choice for diagnosing the presence of stones in the gall-bladder?
Which one of the following biologic agents used in the treatment of inflammatory Bowel Disease acts by inhibiting the enzyme 'Janus Kinase'?
Melanosis coli, which occurs due to long term consumption of stimulant laxatives, presents as brown dis-colouration of colonic mucosa due to
deposition of which one of the following pigments?Consider the following with regard to Gilbert Syndrome:
I. Autosomal recessive trait of a mutation in gene for UDP- glucuronyl transferase enzyme
II. Elevation of unconjugated bilirubin
III. No stigmata of chronic liver disease other than jaundice
IV. Early Liver biopsy recommended in patients with possible Gilbert Syndrome
Which of the above are correct?
