Question

Read the following statements and choose the correct option.
I. Failure of segregation of chromatids during cell division results in aneuploidy.
II. Chromosomal disorders are mainly determined by alternation or mutation in a single gene
III. Thalassemia and cystic fibrosis are Mendelian disorders
IV. Sickle cell anaemia is an X-linked trait
V. Haemophilia is an autosome linked recessive disease.

• A. I and III alone are correct
• B. I, III and IV alone are correct
• C. III and IV alone are correct
• D. II and IV alone are correct
• E. I, III and V alone are correct

Answer 1

The correct option is A I and III alone are correct

• An extra or missing chromosome is a common cause of genetic disorders, including some human birth defects. Aneuploidy originates during cell division when the chromosomes do not separate properly between the two cells.
• Chromosomal disorders may be due to mutations in multiple genes.
• Mendelian disorders result from a mutation at a single genetic locus. Thalassemia and cystic fibrosis are categorized as Mendelian disorders because these are determined by alternation or mutation in a single gene.
  
  • Sickle cell anemia is inherited as an autosomal (meaning that the gene is not linked to a sex chromosome) recessive condition. This means that the gene can be passed on from a parent carrying it to male and female children.
  • Hemophilia is a sex-linked recessive disorder. The gene with the instructions for making factor is found only on the sex chromosome labeled X. If the gene is faulty, the result is hemophilia unless there is a dominant, normal gene on a matching X chromosome.

So, the correct answer is 'I and III alone are correct'.