SEX CHROMATIN DETERMINATION

Every non-egg cell in a womans

body has two X chromosomes:

However, only one of those two X-

chromosomes is active during the life

cycle of that cell.

The other becomes inactivated.

There are two different forms of

inactivation

random

non-random.

Random X-inactivation means that

each X-chromosome has a 50% chance

of being the active chromosome or the

inactive chromosome in that cell.

The selection is completely random.

Therefore, there is a 50% chance that

one of the X will be turned on in the cell

and a 50% chance it will be turned off.

http://www.brooksidepress.org/Products/Military_OBGYN/Textbook/PregnancyProblems/46XX.jpg

Sometimes, a womans X-

inactivation pattern is not random

and the distribution of cells active vs

non-active is not evenly distributed

throughout their body

Barr Body

Barr Body

Barr Body

Normal 46XX female karyotype Trisomy 21 (extra #21 chromosome) in a male (one X

and one Y chromosome)

http://www.brooksidepress.org/Products/Military_OBGYN/Textbook/PregnancyProblems/46XX.jpg

Klinefelter syndrome (KS) is a disorder

that occurs in some men who have

more than one X chromosome (XXY).

Virtually every cell in the body

contains chromosomes, which carry

the genes that determine many of our

physical, intellectual, and emotional

characteristics.

Causes

Males usually inherit a single X chromosome from their

mother and a single Y chromosome from their father.

Males with KS get at least one extra X chromosome from

either their mother or their father.

In most cases there is only one extra chromosome.

The extra X chromosome is caused by a biological

accident.

Normally, an egg has one X chromosome and a sperm has

one X or one Y chromosome.

Occasionally, an egg may end up with two X chromosomes

or a sperm may have both an X and a Y chromosome.

When these abnormal eggs are fertilized by a normal

sperm, or the abnormal sperm fertilizes a normal egg, the

result is a male with two X chromosomes and one Y

chromosome (XXY).

Risk Factors for Klinefelter Syndrome

A risk factor is something that increases

your chances of getting a disease or

condition.

Women over age 35 have a slightly

increased chance of having a child with KS.

There are no other known risk factors for

this disorder.

Symptoms Although the chromosome variation XXY occurs in approximately 1 out

of 1,000 live male births, many men with it do not develop KS.

When KS does develop, it usually goes undetected until puberty and

sometimes much later.

It may present in childhood as learning problems, adolescence as

excessive breast development, in adult life as infertility concerns and as

an unexpected finding on an amniocentesis.

Characteristics may include:

Tallness with extra long arms and legs

Abnormal body proportions (long legs, short trunk)

Enlarged breasts

Lack of facial and body hair

Small firm testes

Small penis

Lack of ability to produce sperm

Diminished sex drive

Sexual dysfunction

Learning disabilities

Personality impairment

Treatment Testosterone

When boys with KS are 10 to 12 years old, their hormone levels are

checked yearly.

If their testosterone levels are low, then treatment with testosterone

may be very helpful.

Men diagnosed in adulthood may also benefit from taking

testosterone.

However, testosterone cannot reverse infertility.

Testosterone is most often given through regular shots in the form of

depotestosterone.

The benefits of this treatment include:

Increased strength

More muscular, male appearance

Growth of facial and body hair

Better self-esteem

Modulation of mood

Increased energy

Increased ability to concentrate

Greater sex drive

A patient with Turner syndrome is shown. This posterior

view shows a low hairline and a shield-shaped chest.

Note the narrow hip development.