Biology Project on
“CHROMOSOMAL DISORDER”
2024-2025
BY: K.Roobesh
GRADE: Xll-B
SCHOOL:THE NGP School,Coimbatore-641018
1. Wolf-Hirschhorn syndrome
Description: Wolf - Hirschhorn syndrome is caused by the deletion of
the distal short arm of chromosome 4. The disorder’s major features
include a characteristic facial appearance, delayed growth and
development, intellectual disability, and seizures.
Signs and symptoms
The most common characteristics include a distinct craniofacial phenotype
(microcephaly, micrognathia, short philtrum, prominent glabella,
ocular hypertelorism, dysplastic ears and periauricular tags), growth
restriction, intellectual disability, muscle hypotonia, seizures, and
congenital heart defects. Less common characteristics
include hypospadias, coloboma of the iris, renal anomalies, and
deafness. Antibody deficiencies are also common, including common
variable immunodeficiency and IgA deficiency. T-cell immunity is normal.
2. Jacobsen Syndrome
Description: Jacobsen syndrome, also known as 11q deletion disorder, results
from a loss of genetic material from the end of the long arm of chromosome .
Signs and symptoms of this condition vary, but most individuals experience
delayed development in motor skills and speech, cognitive impairments,
learning difficulties, and some behavioral problems.
Signs and symptoms
● · Large great toes/Hammer
● Low-platelets toes
(thrombocytopenia)
● Facial/skeletal (dysplasia)
● Wide-set eyes caused by
trigonocephaly
● Folding of the skin near the eye
(epicanthus)
● Short, upturned nose
(anteverted nostrils)
● Thin lips that curve inward
● Displaced receding chin
(retrognathia)
● Low-set, misshapen ears
● · Permanent upward curvature
of the pinkie and ring fingers
(camptodactyly)
3. Angelman syndrome
Description: Angelman syndrome (AS) is an example of genomic imprinting,
where the deletion or inactivation of genes on the maternally inherited
chromosome 15 causes the paternal copy, which may be of normal sequence, to
be imprinted and silenced. AS is characterized by intellectual and developmental
delays, sleep disturbances, seizures, and jerky movements, but also frequent
laughter or smiling and usually have a happy demeanor.
Signs and symptoms:
The following text lists signs and symptoms of Angelman syndrome and
their relative frequency in affected individuals.
Consistent (100%)
● Developmental delay, functionally severe
● Speech impairment, no or minimal use of words; receptive and non-
verbal communication skills higher than verbal ones
● Movement or balance disorder, usually ataxia of gait and/or
tremulous movement of limbs
● Behavioral uniqueness: any combination of frequent laughter/smiling;
apparent happy demeanor; easily excitable personality, often with hand
flapping movements; hypermotoric behavior; short attention span
Frequent (more than 80%)
● Delayed, disproportionate growth in head circumference, usually
resulting in microcephaly (absolute or relative) by age 2
● Seizures, onset usually less than 3 years of age
● Abnormal EEG, characteristic pattern with large amplitude slow-
spike waves
Associated (20–80%)
● Strabismus
● Hypopigmented skin and eyes
● Tongue thrusting; suck/swallowing disorders
● Hyperactive tendon reflexes
● Feeding problems during infancy
● Uplifted, flexed arms during walking
● Prominent mandible
● Increased sensitivity to heat
● Wide mouth, wide-spaced teeth
● Sleep disturbance
● Frequent drooling, protruding tongue
● Attraction to/fascination with water
● Excessive chewing/mouthing behaviors
● Flat back of head
● Smooth palms
4. Turner syndrome
Description: Turner syndrome (TS) occurs when one of the two X
chromosomes in females is either missing or incomplete. The most
common symptoms are short stature and gonadal dysgenesis, which can
cause incomplete sexual development and ovarian failure and infertility.
As of right now, there is no known cause of TS.
Signs and symptoms:
Of the following common symptoms of Turner syndrome, an individual may
have any combination of symptoms and is unlikely to have all symptoms.
● Short stature
● Lymphedema (swelling) of the hands and feet of a newborn
● Broad chest (shield chest) and widely spaced nipples
● Low posterior hairline
● Low-set ears
● Reproductive sterility
● Rudimentary ovaries gonadal streak (underdeveloped gonadal
structures that later become fibrotic)
● Amenorrhoea, the absence of a menstrual period
● Increased weight, obesity
● Shortened metacarpal IV
● Small fingernails
● Characteristic facial features
● Webbed neck from cystic hygroma in infancy
● Aortic valve stenosis
● Coarctation of the aorta
● Bicuspid aortic valve (most common cardiac problem)
● Horseshoe kidney
● Visual impairments – sclera, cornea, glaucoma, etc.
● Ear infections and hearing loss
● High waist-to-hip ratio (the hips are not much bigger than the waist)
● Attention deficit hyperactivity disorder (problems with
concentration, memory, attention with hyperactivity seen mostly in
childhood and adolescence)
Nonverbal learning disability (problems with maths, social skills, and
spatial relations)
5. 22q11.2 deletion syndrome
Description: 22q11.2 deletion syndrome is caused by the deletion of a small
piece of chromosome 22 near the middle of the chromosome. Because signs
and symptoms of 22q11.2 deletion syndrome are varied, different groupings
of symptoms were once described as completely separate conditions,
named DiGeorge syndrome, velocardiofacial syndrome, and conotruncal
anomaly face syndrome.
Signs and symptoms:
The features of this syndrome vary widely, even among members of the same
family, and affect many parts of the body. Characteristic signs and symptoms may
include birth defects such as congenital heart disease, defects in the palate, most
commonly related to neuromuscular problems with closure (velopharyngeal
insufficiency, or VPI), learning disabilities, mild differences in facial features, and
recurrent infections. Infections are common in children due to problems with the
immune system's T-cell-mediated response that in some patients is due to an
absent or hypoplastic thymus. 22q11.2 deletion syndrome (22q11.2DS) may be
first spotted when an affected newborn has heart defects or convulsions from
hypocalcemia due to malfunctioning parathyroid
glands and low levels of parathyroid hormone (parathormone).
Affected individuals may also have other kinds of birth defects including
kidney abnormalities and significant feeding difficulties as babies.
Gastrointestinal issues are also very common in this patient population.
Digestive motility issues may result in constipation.
Disorderssuchas hypothyroidism and hypoparathyroidism or
thrombocytopenia (low platelet levels), and psychiatric illnesses are
common late-occurring features.
Microdeletions in chromosomal region 22q11.2 are associated with a 20 to
30-fold increased risk of schizophrenia. Studies provide various rates of
22q11.2DS in schizophrenia, ranging from 0.5 to 2.0% and averaging about
1.0%, compared with the overall estimated 0.025% risk of the 22q11.2DS in
the general population.
Salient features can be summarized using the mnemonic CATCH-22 to
describe 22q11.2DS, with the 22 signifying the chromosomal
abnormality is found on the 22nd chromosome, as below:
● Cardiac abnormality (commonly interrupted aortic arch,
truncus arteriosus and tetralogy of Fallot)
● Abnormal facies
● Thymic aplasia
● Cleft palate
● Hypocalcemia/hypoparathyroidism
Some experts support changing the name of both DiGeorge and
velocardiofacial syndromes to CATCH-22. The International 22q11.2
Foundation, through its Same Name Campaign, advocates for the
consistent use of 22q11.2 deletion syndrome.
Individuals with a 22q11.2 deletion can have many possible features, ranging in
number of associated features and from the mild to the very serious.
Symptoms shown to be common include:
✔ Congenital heart disease (40% of individuals),
particularly conotruncal malformations (interrupted aortic
arch (50%), persistent truncus arteriosus(34%), tetralogy of
Fallot, and ventricular septal defect)
✔ Cyanosis (bluish skin due to poor circulation of oxygen-rich blood)
✔ Palatal abnormalities (50%), particularly velopharyngeal incompetence,
submucosal cleft palate, and cleft palate; characteristic facial features
(present in the majority of Caucasian individuals) including hypertelorism
✔ Learning difficulties (90%), including cognitive deficits, attention
deficit disorders.
✔ Hypocalcemia (50%)(due to hypoparathyroidism)
✔ Significant feeding problems (30%)
✔ Renal anomalies (37%)
✔ Hearing loss (both conductive and sensorineural) (hearing loss
with craniofacial syndromes)
✔ Laryngotracheoesophageal anomalies
✔ Growth hormone deficiency
✔ Autoimmune disorders
✔ Immune disorders due to reduced T cell numbers
✔ Seizures (with or without hypocalcemia)
✔ Skeletal abnormalities
✔ Psychiatric disorders
This syndrome is characterized by incomplete penetrance. Therefore, there
is a marked variability in clinical expression between the different patients.
This often makes early diagnosis difficult.
6. Triple X Syndrome
Description: Triple X Syndrome is characterized by an extra X chromosome
in each of a female’s cells. It does not cause any unusual physical features
but is associated with the increased risk of learning disabilities and
delayed development of speech and language skills.
signs and symptoms:
Because the vast majority of triple X females are never diagnosed, it may be very
difficult to make generalizations about the effects of this syndrome. The samples
that were studied were small and may be nonrepresentative. Because of the
lionization, inactivation, and formation of Barr bodies in all female cells, only one
X chromosome is active at any time. Thus, triple X syndrome most often has only
mild effects or has no effects. The symptoms vary from person to person, with
some women being more affected than others.
7. Williams Syndrome
Description: Williams’s syndrome is caused by a deletion of genetic material from
portions of the long arm of chromosome 7, a region that consists of more than 25
genes. Researchers have identified a few of the specific genes related to Williams
syndrome, but the relationship between most of the genes in the deleted region
and the symptoms of Williams syndrome is still unknown.
Signs and symptoms:
The most common symptoms of Williams’s syndrome are heart defects
and unusual facial features. Other symptoms include failure to gain
weight appropriately in infancy (failure to thrive) and low muscle tone.
Individuals with Williams’s syndrome tend to have widely spaced teeth, a
long philtrum, and a flattened nasal bridge.
Most individuals with Williams’s syndrome are highly verbal relative to
their IQ, and are overly sociable, having what has been described as a
"cocktail party" type personality. Individuals with WS hyperfocus on the
eyes of others in social engagements
8. Cri du Chat Syndrome
Description: Cri du Chat syndrome results from missing a piece of chromosome
5. Symptoms include a high-pitched cry that sounds like a cat, downward
slant of the eyes, partial webbing or fusing of fingers or toes, and slow or
incomplete development of motor skills.
Signs and symptoms:
The syndrome gets its name from the characteristic cry of affected infants,
which is similar to that of a meowing kitten, due to problems with the larynx
and nervous system. About 1/3 of children lose the cry by age of 2 years.
Other symptoms of cri du chat syndrome may include:
● feeding problems because of difficulty in swallowing and sucking;
● low birth weight and poor growth;
● severe cognitive, speech, and motor delays;
● behavioral problems such as hyperactivity, aggression, outbursts,
and repetitive movements;
● unusual facial features which may change over time;
● excessive drooling;
● small head and jaw;
● wide eyes;
● skin tags in front of eyes.
Other common findings include hypotonia, microcephaly, growth retardation,
a round face with full cheeks, hypertelorism, epicanthal folds, down-
slanting palpebral fissures, strabismus, flat nasal bridge, down-turned
mouth, micrognathia, low-set ears, short fingers, single palmar creases,
and cardiac defects (e.g., ventricular septal defect[VSD], atrial septal
defect [ASD], patent ductus arteriosus [PDA], tetralogy of Fallot).
Infertility is not associated with Cri du chat.
It has also been observed that people with the condition have
difficulties communicating. While levels of proficiency can range from a
few words to short sentences, it is often recommended by medical
professionals for the child to undergo some sort of speech therapy/aid
with the help of a professional.
Less frequently encountered findings include cleft lip and palate, preauricular
tags and fistulas, thymic dysplasia, intestinal malrotation, megacolon, inguinal
hernia, dislocated hips, cryptorchidism, hypospadias, rare renal malformations
(e.g., horseshoe kidneys, renal ectopia or
agenesis, hydronephrosis), clinodactyly of the fifth fingers, talipes
equinovarus, pes planus, syndactyly of the second and third fingers and
toes, oligosyndactyly, and hyperextensible joints. The syndrome may
also include various dermatoglyphics, including transverse flexion
creases, distal axial triradius, increased whorls and arches on digits, and
a single palmar crease.
Late childhood and adolescence findings include significant intellectual
disability, microcephaly, coarsening of facial features, prominent
supraorbital ridges, deep-set eyes, hypoplastic nasal bridge, severe
malocclusion, and scoliosis.
Affected females reach puberty, develop secondary sex characteristics, and
menstruate at the usual time. The genital tract is usually normal in females
except for a report of a bicornuate uterus. In males, testes are often small,
but spermatogenesis is thought to be normal.
9. Trisomy 13
Description: Trisomy 13, also called Patau syndrome, is a disorder in which
an individual has three copies of genetic material from chromosome 13,
rather than two. It can occur in three forms: Trisomy 13, which has a third
chromosome 13 in all cells; Trisomy 13 mosaicism, which has a third
chromosome 13 in some cells; and partial Trisomy, which has the presence
of part of an extra chromosome 13 in the cells.
Signs and symptoms:
Of those fetuses that do survive to gestation and subsequent birth,
common abnormalities may include:
⮚ Nervous system
● Intellectual disability and motor disorder
● Microcephaly
● Holoprosencephaly (failure of the forebrain to divide properly).
● Structural eye defects, including microphthalmia, Peters'
anomaly, cataract, iris or fundus (coloboma), retinal dysplasia or
retinal detachment, sensory nystagmus, cortical visual loss, and optic
nerve hypoplasia
● Meningomyelocele (a spinal defect)
⮚ Musculoskeletal and cutaneous
● Polydactyly (extra digits)
● Cyclopia
● Proboscis
● Congenital trigger digits
● Low-set ears
● Prominent heel
● Deformed feet known as rocker-bottom feet
● Omphalocele (abdominal defect)
● Abnormal palm pattern
● Overlapping of fingers over thumb
● Cutis aplasia (missing portion of the skin/hair)
⮚ Urogenita
Abnormal genitalia
Kidney defects
⮚ Other
∙
Heart defects (ventricular
∙
septal defect) (Patent Ductus
∙ Arteriosus) Dextrocardia
Single umbilical artery
10. Cat eye syndrome
Description: For individuals with cat eye syndrome, the short arm (known
as 22p) and a small region of the long arm (22q) of chromosome 22 are
present three or four times, rather than twice. Characteristic features of
the disorder include mild growth delays before birth, mild mental
deficiency, and malformations of the skill and facial region, the heart, the
kidneys, and/or the anal region.
Signs and symptoms:
● Unilateral or bilateral iris coloboma (absence of tissue from the
colored part of the eyes)
● Downward-slanting Palpebral fissures (openings between the upper
and lower eyelids)
● Preauricular pits/tags (small depressions/growths of skin on the outer ears)
● Cardiac defects (such as TAPVR)
● Kidney problems (missing, extra, or underdeveloped kidneys)
● Short stature
● Scoliosis/Skeletal problems
● Intellectual disability – although most are intellectually normal,
CES patients occasionally exhibit moderate to severe disability.
● Micrognathia (smaller jaw)
● Hernias
● Cleft palate
● Rarer malformations can affect almost any organ
Bibliography
Websites:
♦ Wikipedia
http://en.m.wikipedia.org/
♦ National Human Genome Research Institute
http://www.genome.gov/
♦ Genetic and Rare Diseases Information Center
http://rarediseases.info.nih.gov/
♦ Genetic Home Reference
http://ghr.nlm.nih.gov/
♦ The University of Chicago – Pediatrics Clerkship
http://pedclerk.bsd.uchicago.edu/
♦ National Health Service, England.
http://www.nhs.uk/
♦ Mayo Clinic
http://www.mayoclinic.org/
Books:
♦ Class 12 – Biology NCERT
♦ Chromosomal Aberrations, A.T.Natarajan.
♦ Abnormal Karyotypes.
♦ Chromosomal Abnormalities and Genetic Counselling,
R.J.M.Gardner and G.R.Sutherland.
