AP BIOLOGY

THE MOLECULAR BASIS OF INHERITANCE

THE HUMAN GENOME

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
What genetic disorder results in 45 chromosomes in each of the body cells? (3.2.2)
A
Turner’s syndrome
B
Down syndrome
C
Klinefelter’s
D
Jacobs syndrome
Explanation: 

Detailed explanation-1: -Mosaic Turner syndrome: Also called 45, X mosaicism, this type makes up about 30% of Turner syndrome cases. Some of the baby’s cells have a pair of X chromosomes, while other cells only have one. It happens randomly during cell division early in pregnancy.

Detailed explanation-2: -There are 2 types of Turner syndrome: monosomy X TS and mosaic TS. About half of all girls with Turner syndrome have a monosomy disorder. Monosomy means that a person is missing one chromosome in the pair. Instead of 46 chromosomes, the person has only 45 chromosomes.

Detailed explanation-3: -Overview. Turner syndrome, a condition that affects only females, results when one of the X chromosomes (sex chromosomes) is missing or partially missing. Turner syndrome can cause a variety of medical and developmental problems, including short height, failure of the ovaries to develop and heart defects.

Detailed explanation-4: -While most people have 46 chromosomes, people with Turner syndrome usually have 45 in some or all cells. The chromosomal abnormality is often present in just some cells, in which case it is known as Turner syndrome with mosaicism. In these cases the symptoms are usually fewer, and possibly none occur at all.

Detailed explanation-5: -To diagnose Turner syndrome, doctors use a special blood test that looks at chromosomes, called a karyotype test (chromosomal analysis). Results that indicate TS show only one X chromosome instead of two X chromosomes, with a total of 45 chromosomes instead of the usual 46.

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