Université Echahid HAMMA LAKHDAR D’El-Oued

Faculté des Sciences de La Nature et de La Vie

Département de biologie cellulaire et moléculaire
Niveau : 2 éme master toxicologie Module : Génétique et pathologie humaines
Trisomy
Présenter par : DJABER Hana, KADDOURI Hadda, TAMMA Arwa, BOUAFIA Islam
Dirigé par : AZZI Manal
Abstract
Trisomy is a genetic condition that occurs when an individual has three copies of a particular chromosome instead of the usual two. This condition
is known by different names depending on the chromosome involved, such as trisomy 21, also known as Down syndrome, trisomy 13, and trisomy
18. Individuals with trisomy have unique physical and psychological characteristics, and their families may face multiple challenges in terms of care
and support. The aim of this article is to understand the causes of trisomy, its types, symptoms, how it is diagnosed and managed, and its impact on
the lives of individuals and their families. By understanding trisomy more deeply, society can provide the necessary support and improve the quality
of life for affected individuals.
Keywords; Trisomy, chromosome, Trisomy 21, Trisomy 13,Trisomy 18

Material and methode 2/Cause of Trisomy

◇International Journal Dental and Medical Sciences ◇A normal egg cell and normal sperm cell start with 46
Research chromosomes when a baby is conceived
Volume 3, Issue 1, Jan-Feb 2021 pp 805-810 ◇The egg and sperm cells divide in half, each possessing 23
www.ijdmsrjournal.com ISSN: 2582-6018 chromosomes.
◇Google scholar ◇After fertilization, the baby will have a complete set of 46
◇Science direct chromosomes.
Introduction ◇But sometimes, an error can occur when dividing 46
Trisomy is a genetic condition caused by an extra copy of a chromosomes in half. Either egg or sperm cell may keep both
particular chromosome in an individual’s cells. This disorder copies of a chromosome instead of just one copy.
can affect growth and development, and lead to a variety of ◇The baby will have three copies of chromosomes if this egg
physical and cognitive symptoms. or sperm is fertilized. The cause is unknown, and prevention
The most common type of trisomy is trisomy 21, also known is not possible.
as Down syndrome. Symptoms associated with this condition
◇Trisomy 13 occurs when the baby has three copies of
include delayed development, distinctive facial features, and
chromosome number 13.
chronic health problems. There are also other types of
◇Trisomy 18 occurs when the baby has three copies of
trisomy, such as trisomy 18 (Edwards syndrome) and trisomy
chromosome number 18.
13 (Patau syndrome), each of which is associated with
different health and developmental problems. ◇Trisomy 21 occurs when the baby has three copies of
Understanding trisomy requires studying the genes and chromosome number 21.
chromosomes, as well as the environmental factors that may ◇This extra copy of a chromosome is then present in every
contribute to these conditions. Psychosocial support for cell in the body.
affected individuals and their families is also an essential part ◇Sometimes the extra chromosome, or part of it, is attached
of managing these disorders. to another chromosome in the egg or sperm. ◇This is called
Results and discussions: translocation. This is the only form of trisomy that may be
1/Definition inherited from a parent. Some parents may have balanced
Trisomy is a genetic condition caused by an alteration in the translocation.
number of chromosomes where the affected person has three ◇This means the chromosome is attached to another
copies of one of the chromosomes instead of two. The chromosome. However, it has no impact on their health
affected person possesses 47 chromosomes instead of 46. The most important risk factor for trisomy conditions is
maternal age.
Women in their late 30s and 40s have a higher chance of
trisomy conditions occurring
Paternal age does not seem to be associated with the incidence
of trisomy
3/Types of Trisomy in Humans
The most common trisomy conditions include:
◇Trisomy 13 (Patau syndrome(
◇Trisomy 18 (Edward syndrome(
◇Trisomy 21 (Down syndrome)

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A_ Trisomy 13 (Patau syndrome) Pregnant women who previously had infectious hepatitis may
Trisomy 13 is also known as Patau syndrome. have a threefold increased risk of giving birth to children with
It was described in 1960 by Klaus Patau and coworkers. Down syndrome.
It occurs in about 1 in 8000 to 12000 newborns. ◇TYPES OF DOWN SYNDROME
◇Some of the characteristics of Trisomy 13 include: Three variants of DS are as follows:
•Low birth weight 1) Mosaic Down`s syndrome: Is the least common pattern of
•Small skull (microcephaly) transmission of DS, occurring in 1-2% of people with DS and
•An abnormal opening in the skull the error in cell division occurs after fertilization. Affected
•Structural problems of the brain, such as the front of the brain individuals have mixture of 47 or 46 chromosomes, an extra
not divided normally (holoprosencephaly) chromosome is present in 47 containing group.
•Eyes that are close together The greater number of normal cells in DS, the higher the
•Low-set ears that have unusual shape chances of higher cognitive functions ,with a possibility of
•Scalp abnormalities that resemble ulcers less intellectual impairment.[9]This type of DS is not
•Cleft lip or Cleft palate inherited.
•Additional toes or fingers (polydactyly) 2( Translocation Down syndrome
•Congenital heart disorders, such as ventricular septal defect This type accounts for a small percentage of people with
•Neural tube defect where the spinal cord, meninges and Down syndrome (about 3%) and is inheritable.
blood vessels protrude through a gap in the vertebrae This occurs when an extra part or a whole extra chromosome
(myelomeningocele) 21 is present, but it is attached or “trans-located” to a different
•In boy babies, testes do not descend into the scrotum chromosome rather than being a separate chromosome 21.
•In girl babies, uterus that forms in 2 branches (bicornuate 3 )Non disjunction Down`s syndrome: Trisomy 21 is most
uterus) is formed common type of DS. The error begin in either the sperm or
•It is rare for babies to survive past the neonatal stage with the egg , with the presence of the extra chromosome before
Patau syndrome. the egg and sperm unite. Trisomy 21 compromises about
◇Most babies born with trisomy 13 die by age 1. There are a 95% of all cases. Non disjunction causing Trisomy 21 is of
few reports of babies with trisomy 13 surviving to their teens maternal origin in about 88% of cases and occurs more
B/ Trisomy 18 (Edward syndrom) frequently in older cells ,which accounts for older women
Trisomy 18 is also known as Edward syndrome. giving birth to offspring with Trisomy 21.
It occurs in about one out of every 6000 to 8000 newborns.
◇Characteristics of Trisomy 18 include:
•Small skull (microcephaly)
•Physical irregularity of the kidneys, ureters, heart, lungs and
diaphragm
•Cleft lip or Cleft palate
•Malformations of the hands and feet such as missing thumbs,
club feet and webbing between the fingers and toes
(syndactyly(
•Neural tube defect where the spinal cord, meninges and ◇Some properties of Down syndrome
blood vessels protrude through a gap in the vertebrae Down syndrome can present a variety of physical and
(myelomeningocele( developmenta symptoms. Common signs and features
•In boy babies, testes do not descend into the scrotum include:
•It is rare for babies to survive past the neonatal stage with .1Physical Features:
Edward syndrome -A flat facial profile
.Trisomy 21 (Down syndrome) C. -Slanted eyes, often with an epicanthic fold
•Trisomy 21 is also known as Down syndrome. -A short neck
•Down syndrome is named after the physician J. Langdon -Small ears
•Down who first described this genetic defect in 1866. It was -A protruding tongue
formally called mongolism or mongolian idiocy. -Short stature
•It affects about 1 in 800 babies. -A single transverse palmar crease (simian line)
•The average lifespan of an adult with Down syndrome is 60 -Wider space between the first and second toes
years, though this can vary. .2Developmental Delays:
Trisomy 21 is found to be affected either by senescence of -Delayed physical development and growth
oocytes, virus infection, radiation damage, etc. -Language and speech delays
-Cognitive impairment, with varying degrees of intellectual
disability

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 -Challenges with motor skills (fine and gross) •Tremors
.3Health Issues: Osteoporosis (weakened bones)
-Increased risk of heart defects •Autoimmune diseases (Thyroid disease, Lupus and
-Gastrointestinal issues (e.g., duodenal atresia) Rheumatoid arthritis)
-Hearing problems 3•Jacob’s syndrome:
-Vision problems, including cataracts and refractive errors It is a genetic condition characterized by an extra copy of the
-Thyroid problems Y chromosome in each of an individual’s cells.
.4Behavioral Characteristics: It affects about 1 in 1,000 newborns.
-Friendly and social temperament It is not inherited.
-May exhibit stubbornness or strong-willed behavior During the formation of sperm cells, a random chromosomal
-Increased likelihood of developing certain behavioral issues, change may occur. An error in cell division called
like attention-deficit/hyperactivity disorder (ADHD) nondisjunction can result in sperm cells with an extra copy of
It's important to remember that individuals with Down the Y chromosome.
syndrome vary widely in their abilities and health conditions. ◇Some of the characteristics of Jacob’s syndrome
Regular medical checks and early intervention programs can include:
help improve development and health outcomes. •Hypotonia (weak muscle tone)
3:Types of sex cell Trisomy in humans •Delayed motor skill development, such as with walking or
It includes crawling
•Trisomy X (XXX) •Delayed or difficult speech
•Klinefelter syndrome (XXY) •Autism diagnosis
•Jacob’s syndrome (XYY) •Attention difficulties
1 .Trisomy X Hand trembling or involuntary muscle movements
It is a genetic condition where a female is born with an extra •Learning disabilities
X chromosome. •Taller-than-average height
This condition occurs only in females. )4Signs of Trisomy
It occurs in about 1 in 1,000 female newborns. 1)During Pregnancy
It is not usually inherited from an affected parent. •Too much amniotic fluid surrounding the baby
The majority of cases are entirely random occurrences that are (polyhydramnios)
caused by errors in chromosome replication and division •Only one umbilical cord artery
during the formation of egg or sperm cells. •Smaller than expected placenta
•Some of the characteristics of Trisomy X include: •The baby is small for its gestational date.
◇Taller than girls of the same age and/or taller than predicted •Baby is less active than expected
by their parents’ heights •Congenital defects, including cleft palate or heart
◇Wide-spaced eyes known as hypertelorism irregularities, are picked up during ultrasound scans.
◇Vertical skin folds that cover the inner corners of the eyes 2)postpartum
(known as epicanthal folds) •Small stature.
◇Curved or bent little fingers (known as clinodactyly) •Round face with a flat profile.
•Slanted eyes.
◇Poor muscle tone (known as hypotonia)
•Cleft palate.
◇Premature ovarian aging or failure
•Organs forming or working abnormally (heart, lungs or
◇Genito-urinary deformities kidney).
◇Attention deficit disorder •Developmental delays and intellectual disabilities
2_Klinefelter syndrome 5_ Diagnosis of Trisomy condition:
It is a genetic condition where a male is born with an extra X Prenatal tests that can help detect trisomy disorders include:
chromosome. ◇Ultrasound scans: Sound waves are used to create a picture.
It affects about 1 in 650 newborn boys.
◇Maternal Serum Screening: A specialized blood test. Two
Klinefelter syndrome is not inherited; the addition of an extra
serum screening tests are available to all women.
X chromosome occurs during the formation of reproductive
Combined First Trimester Screening (CFTS)
cells (eggs or sperm) in one of an affected person’s parents.
Second Trimester
◇Some of the characteristics of Klinefelter syndrome
◇Maternal Serum Screening (2TMSS)
include:
◇Amniocentesis: Between 15 and 20 weeks of pregnancy, a
•Hypertension (high blood pressure)
sample of the amniotic fluid is taken and examined.
•Type 2 diabetes
•High cholesterol and fats in the blood ◇Chorionic villus sampling (CVS): Between 10 and 13
•Gynecomastia (breast growth in a male) weeks of pregnancy, a sample of cells from the chorion, the
•Breast cancer

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tissue that will ultimately become the placenta, is taken and future lies in scientific progress and community collaboration
examined. to achieve a better life for people living with trisomy.
◇Non-invasive prenatal testing (NIPT): After ten weeks of Références
pregnancy, a screening test that measures fetal DNA 1. 9500 Euclid Avenue, Cleveland, Ohio 44195 |
800.223.2273 | © 2024 Cleveland Clinic. All Rights
circulating in the mother’s blood.
Reserved.
◇Percutaneous umbilical blood sampling (PUBS): A small 2. https://my.clevelandclinic.org/health/diseases/22912-
blood sample from a baby’s umbilical cord to test for health trisomy
conditions 3. August 3, 2023 by Dibyak Kapali
6:Treatment of Trisomy 4. Edited By: Sagar Aryal
1)Medical Care 5. 2024 Microbe Notes. Made with by Sagar Aryal.
6. https://microbenotes.com/trisomy-types-characteristics/
Drug therapy is not a component of the standard of care for
7. WELLNESS HUB
trisomy. 8. Last Updated: October 21, 2023
Nasogastric and gastrostomy supplementation for feeding 9. https://www.mywellnesshub.in/blog/down-syndrome/
problems. 10. https://wecapable.com/down-syndrome-types-causes-
Orthopedic management of scoliosis may be needed. symptoms-treatment/
Cardiac management is primarily medical. Most of the 11. A Current Knowledge of “Down Syndrome: A Review
children require a diuretic and digoxin for congestive heart 12. Dr. Shilpa karkeraInternational Journal Dental and
Medical Sciences Research
failure.
13. Volume 3, Issue 1, Jan-Feb 2021 pp 805-810
Neonatal intensive care (NICU) management www.ijdmsrjournal.com ISSN: 2582-6018
2)Periodic screenings 14. A Current Knowledge of “Down Syndrome: A Review”
Periodic screenings throughout childhood and into adulthood 15. Dr. Shilpa karkera
may be advised by the healthcare professional. 16. Assistant professor Department of Anatomy &
Treatment can be given immediately for any health issues, Neuroscience Trinity School of Medicine Ratho mill,
learning difficulties, or developmental delays. Kingstown St
17. Vincent & Grenadines
3)Early intervention services 18. International Journal Dental and Medical Sciences
These services may start in the first few months of life or as Research
soon as requirements are recognized and may include speech, 19. Volume 3, Issue 1, Jan-Feb 2021 pp 805-810
occupational, physical, or developmental therapy. www.ijdmsrjournal.com ISSN: 2582-6018
4)Educational assistance
If the child has a learning disability, educational help to learn
techniques and strategies to be successful in school and daily
life can be provided.
5)Psychosocial management
About issues of diagnosis and survival.
Parents should be informed properly about the syndrome,
including its cause, implications, and possible outcomes.
6)Assistance and support in daily functioning
If a child’s difficulties interfere with everyday functioning,
this support and assistance may include help with social
interactions, work, and daily living activities
Conclusion
In conclusion, trisomy is a complex genetic condition that
requires a deep understanding from the medical community
and families. We have reviewed the various causes and
symptoms of this condition, as well as the currently available
diagnostic and management methods. The psychological and
social impacts of trisomy emphasize the need for ongoing
support and awareness in the community. Through ongoing
research and innovations in treatment and support, the quality
of life for individuals affected by trisomy can be improved,
and they can be given better opportunities to achieve their
potential. Promoting understanding and acceptance in the
community is an essential step towards removing stigma and
providing a supportive environment for everyone, regardless
of the genetic challenges they may face. The hope for the