Question

Karyotype of Turner's syndrome is

• A. 45, X [AA + XO]
• B. 47, XXY [AA + XXY]
• C. 47, XX + 13
• D. 47, XX + 18

Hint:

Turner's syndrome affects phenotypic females (sterile ovaries, webbed neck). It is the only viable monosomy in humans.

Answer 1

The Correct Option is A

Step 1: Understanding Turner's Syndrome:
Turner's syndrome is a chromosomal disorder in females caused by the absence of one of the X chromosomes. This is a case of monosomy $(2n - 1)$.
Step 2: Analyzing the Karyotype:

• Normal Human Karyotype: 46 chromosomes (44 autosomes + 2 sex chromosomes).
• Turner's Syndrome: Loss of one X chromosome.
• Total Chromosomes: $46 - 1 = 45$.
• Sex Chromosomes: Only one X is present (denoted as XO).
• Notation: 45, X or sometimes written with autosomes as AA + XO.

Step 3: Analyzing Other Options:
(B) 47, XXY represents Klinefelter's Syndrome.
(C) 47, XX + 13 represents Patau Syndrome (Trisomy 13).
(D) 47, XX + 18 represents Edwards Syndrome (Trisomy 18).
Step 4: Final Answer:
The correct karyotype is 45, X [AA + XO].