genetic disease

4. Mosaicism is a condition in which cells within the
same person have a different genetic makeup. This
condition can affect any type of cell, including:
• Blood cells
• Egg and sperm cells (gametes)
• Skin cells
Causes
Mosaicism is caused by an error in cell division very
early in the development of the unborn baby.
Examples of mosaicism include:
• Mosaic Down Syndrome
• Mosaic Klinefelter Syndrome
• Mosaic Turner Syndrome

7. Klinefelter syndrome, also known as the XXY condition, is a term used to describe
males who have an extra X chromosome in most of their cells. Instead of having the
usual XY chromosome pattern that most males have, these men have an XXY pattern.
Taller than average stature.
Longer legs, shorter torso and
broader hips compared with other boys.
Absent, delayed or incomplete puberty.
After puberty, less muscle and
less facial and body hair compared with
other teens.
Enlarged breast tissue (gynecomastia)

8. Triple X syndrome, also known as trisomy X and 47,XXX, is
characterized by the presence of an extra X chromosome in each
cell of a female. Those affected are often taller than average.
taller than average
Complications Learning
difficulties, decreased muscle
tone, seizures, kidney
problems

10. • In humans, a sex-chromosome monosomic complement
of 44 autosomes + 1 X produces a phenotype known
as Turner syndrome.
• Turner syndrome is related to the X chromosome, which
is one of the two sex chromosome.
• About half of individuals with Turner
syndrome have monosomy X, which means each cell in
the individual's body has only one copy of the X
chromosome instead of the usual two sex
chromosomes.
• Turner syndrome can also occur if one of the sex
chromosomes is partially missing or rearranged rather
than completely absent.
• Some Women with Turner syndrome caused by X
chromosome mosaicism are said to have mosaic Turner
syndrome.

12. • Trisomy (‘three bodies’) means the affected person has
47 chromosomes instead of 46. Down syndrome,
Edward syndrome and Patau syndrome are the most
common forms of trisomy. Children affected by trisomy
usually have a range of birth defects, including delayed
development and intellectual disabilities.
Risk factors for birth defects
• The addition of an extra chromosome usually occurs
spontaneously during conception. The cause of this is
unknown and prevention is not possible. The most
important risk factor for trisomy disorders is maternal
age. Women in their late 30s and 40s are more likely to
have babies with trisomy than younger women.

14. Edwards syndrome

15. Trisomy-18 (2n=46,18+) (Edward Syndrome) is the second most common trisomy after Down
Syndrome, and occurs in 1 / 4 ~ 8000 live births. It is three times as prevalent in newborn girls as
in boys. Trisomy 18 is characterized by microcephaly, a high forehead, profound psycho-motor
retardation, and serious heart malformations. Life expectancy is typically very short: 90% of
children die in the first year. Katrina (upper left) lived only a few months. In contrast, Joseph
(middle & right) lived to two months short of 22 years.

17. • Individuals with trisomy 13 often have heart defects,
brain or spinal cord abnormalities, very small or poorly
developed eyes (microphthalmia), extra fingers or toes,
an opening in the lip (a cleft lip) with or without an
opening in the roof of the mouth (a cleft palate), and
weak muscle tone (hypotonia). Due to the presence of
several life-threatening medical problems, many infants
with trisomy 13 die within their first days or weeks of
life. Only five percent to 10 percent of children with this
condition live past their first year.
• Most cases of trisomy 13 result from having three copies
of chromosome 13 in each cell in the body instead of the
usual two copies. The extra genetic material disrupts the
normal course of development, causing the
characteristic features of trisomy 13.

19. Down syndrome

20. What is Down syndrome?
• Down syndrome is a set of physical and mental
traits caused by a gene problem that happens
before birth. Children who have Down
syndrome tend to have certain features, such as
a flat face and a short neck. They also have
some degree of intellectual disability. This varies
from person to person. But in most case it is
mild to moderate.
• Down syndrome is a lifelong condition. But with
care and support, children who have Down
syndrome can grow up to have healthy, happy,
productive lives.

22. How is Down syndrome diagnosed?
• Your doctor may suggest that you have tests during
pregnancy to find out if your baby has Down syndrome. You
may decide to have:
• Screening tests, such as an ultrasound or a blood test during
your first or second trimester. These can help show if
the developing baby(fetus) is at risk for Down syndrome.
But these tests sometimes give false-positive or false-
negative results.
• Diagnostic tests, such as chorionic villus
sampling or amniocentesis. These can show if a baby has
Down syndrome.
• Sometimes a baby is diagnosed after birth. A doctor may
have a good idea that a baby has Down syndrome based on
the way the baby looks and the results of a physical exam.
To make sure, the baby's blood will be tested. It may take 2
to 3 weeks to get the test results.

24. Down syndrome

25. Polyploidy

29. Prader-Willi syndrome
Prader-Willi syndrome
• Symptoms include learning difficulties, short stature, and compulsive eating.
• Individuals are missing gene activity that normally comes from dad.
• Happens when dad's copy is missing, or when there are two maternal copies.

30. Angelman syndrome
• Symptoms include learning difficulties, speech problems, seizures, jerky
movements, and an unusually happy disposition.
• Individuals are missing gene activity that normally comes from mom.
• Happens when mom's copy is defective or missing, or when there are two
paternal copies.

31. Summary
• In females, one X chromosome, maternal or paternal, is randomly
inactivated during development.
• In Klinefelter syndrome, there are two or more X chromosomes with one Y
chromosome as a result of nondisjunction of sex chromosomes.
• Patients have testicular atrophy, sterility, reduced body hair,
gynecomastia, and eunuchoid body habitus. It is the most common cause
of male sterility.
• In Turner syndrome, there is partial or complete monosomy of genes on
the short arm of the X chromosome, most commonly due to absence of
one X chromosome (45,X) and less commonly from mosaicism, or from
deletions involving the short arm of the X chromosome.
• Short stature, webbing of the neck, cubitus valgus, cardiovascular
malformations, amenorrhea, lack of secondary sex characteristics, and
fibrotic ovaries are typical clinical features.

32. References
• Robbins Pathology 10th edition
• Thompson and Thompson Genetics 7th edition
• Google Images
• https://www.genome.gov/For-Patients-and-
Families/Genetic-Disorders
• https://www.msdmanuals.com/home/childre
n-s-health-issues/chromosome-and-gene-
abnormalities/overview-of-chromosome-and-
gene-disorders