Alzheimer's disease is an example of autosomal recessive disorder.

The following family tree traces the occurrence of a rare genetic disease. The filled symbols signify the individuals with the disease, whereas the open symbols signify healthy individuals.

Based on this information, the disease is most likely to be:

Pick out the correct statements:

(i) Colour blindness is a sex-linked recessive gene disorder.

(ii) Klinefelter's syndrome is 18^th chromosomal trisomy.

(iii) Phenylketonuria is an autosomal dominant genetic disorder.

(iv) Down’s syndrome is due to aneuploidy.

Fill in the blank with the correct word given in the bracket.

_____ (Klinefelter/Down) syndrome is a chromosomal variation in males in which one extra X chromosome is present.