SNP Shot: Genomic Insights

Turner syndrome is a genetic disorder that affects individuals assigned female at birth. It's characterized by the absence of one X chromosome or an abnormality in one of the X chromosomes. Typically, females have two X chromosomes, but those with Turner syndrome have only one fully working copy.

A key feature of Turner syndrome is short height, often becoming apparent around the age of 5. Impaired ovarian function is also common. Although ovaries initially develop normally, egg cells usually die off early, resulting in significant ovarian tissue deterioration before birth.

Many individuals with Turner syndrome need hormone replacement therapy to induce puberty and frequently face infertility. However, a small minority maintain normal ovarian function into their early adult years.

Around 30% of individuals with Turner syndrome display additional characteristics, including a webbed neck, a low hairline at the back of the neck, swelling in the hands and feet due to lymphedema, skeletal problems, or kidney abnormalities. Between 30% and 50% are born with heart defects, such as coarctation of the aorta or abnormalities of the aortic valve. These heart problems can be life-threatening.

People with Turner syndrome generally have normal intelligence. However, some might experience developmental delays, nonverbal learning difficulties, or behavioral issues, although the presence and severity of these characteristics vary among individuals.

Inheritance:

Most instances of Turner syndrome are not passed down through families. Monosomy X, a frequent cause, results from a chance error during the formation of egg cells or sperm cells in the parent. This error, known as nondisjunction, leads to reproductive cells with an incorrect number of chromosomes. For example, an egg or sperm cell could lose a sex chromosome due to nondisjunction. If such a cell participates in the child's genetic makeup, the child will have only one X chromosome in each cell.

Mosaic Turner syndrome is also not hereditary. It's caused by a random error in cell division during early fetal development. As a result, some cells possess two sex chromosomes, while others possess only one. Other mosaic patterns involving sex chromosomes are also possible.

In rare cases, Turner syndrome resulting from a partial deletion of the X chromosome can be inherited.