Principles Of Inheritance And Variation

Chromosomal disorders are genetic conditions caused by an abnormality in the number or structure of an individual's chromosomes. These abnormalities, known as chromosomal aberrations, arise from errors during gamete formation (meiosis), such as the failure of chromosomes to separate properly (non-disjunction). This results in a zygote with an abnormal number of chromosomes (aneuploidy) or structurally altered chromosomes, leading to a range of physical and developmental problems. Turner's Syndrome:

Cause: It is a chromosomal disorder caused by the absence of one of the X chromosomes in females. It is a monosomy of the sex chromosome, resulting in a karyotype of 45, XO instead of the normal 46, XX.
Symptoms: Individuals with Turner's syndrome are females with the following characteristics:

They are sterile because their ovaries are rudimentary and non-functional.
They have a short stature.
Physical features often include a broad, "shield-like" chest with widely spaced nipples, a webbed neck, and a low hairline at the back of the neck.
They lack secondary sexual characteristics at puberty.
Intelligence is generally normal, though some may have learning difficulties, particularly with spatial visualization.

Klinefelter's Syndrome:

Cause: This disorder is caused by the presence of an extra X chromosome in males. It is a trisomy of the sex chromosome, resulting in a karyotype of 47, XXY instead of the normal 46, XY.
Symptoms: Individuals with Klinefelter's syndrome are males who may exhibit the following characteristics:

They are sterile due to underdeveloped, small testes (testicular atrophy) and no sperm production (azoospermia).
They are often tall with disproportionately long arms and legs.
They have overall masculine development but also show some feminine characteristics, most notably the development of breast tissue (gynaecomastia).
They have sparse body and facial hair.
Testosterone levels are low, and they may have learning disabilities or delayed speech development.