CARMEL ENGLISH MEDIUM SCHOOL , JATNI

BIOLOGY INVESTIGATORY PROJECT 2024_2025

STUDY ABOUT CHROMOSOMAL DISORDER

Submitted By : Submitted To
Sangram pani
 ACKNOWLEDGEMENT
I take this opportunity to express my gratitude to all those
who have helped me in completing the project entitled
“CHROMOSOMAL DISORDERS” for the partial
fulfillment of “AISSCE 2024-2025”.
I am extremely thankful to my principal Mrs. Arupama
Routray for her willing help and valuable guidance.
I thank my Biology teacher Mrs. Banadurga Saha for her
guidance and constant encouragement and critical
analysis.
At last, but not the least, I would like to thank CBSE for
giving this opportunity to undertake this project.

Submitted By:
AISSCE Roll No. :
 CERTIFICATe

This is to certify that Master/ Miss Sangram pani of class-XII

Science, bearing the AISSCE Roll No. has
prepared and submitted this Biology Investigatory project
entitled topic
“Study Of Chromosomal Disorders” in partial fulfillment of
AISSCE; 2024-25 of CBSE, under my personal guidance and
supervision.

I wish him all success in life.

DATE:

Counter signature:

Signature of Internal Signature of External:

 CONTENT
INTRODUCTION

DOWN’S SYNDROME
(Description, signs and symptoms, cause, complication)

TURNER’S SYNDROME
(Description, signs and symptoms, cause, complication)

KLINFELTER’S SYNDROME
(Description, signs and symptoms, cause, complication)

OTHER CHROMOSOMAL DISORDERS

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 INTRODUCTION

Genetics deals with the inheritance, as well as the variation of characters from
parents to offspring. Inheritance is the process by which characters are passed from
the parent to progeny. It is the basis of heredity; variation is the degree by which
progeny differ from their parents.

→What is a disorder?

When any of the organs of an organism is malfunctioning, then he/she is having

some disorder. But whenever some changes in gene structure due to alterations in
nucleotide number, type, or sequence cause gene mutation, which is a cause of
genetic disorder.

→How to identify a genetic disorder ?

It can be identified by pedigree Analysis.

Pedigree is a chart showing a record of inheritance & certain traits for two or more
ancestral generations of human being or domesticated animal in the form of a
diagram & family- tree.

The analysis of traits in several generations of a human family in the form of a

family diagram is called Pedigree Analysis. It serves as a strong tool which is
utilized to trace the inheritance of a specific trait, abnormality or disease.

Inheritance pattern of traits in human beings cannot be studied by crosses as in

case of other organisms due to following reasons.

(i)The produced progeny is very small (usually one) and takes long time in
development.

(ii) Controlled crosses cannot be performed. The standard symbols used in

pedigree analysis are given in figure 1
.

Figure 1: symbol used in the human pedigree analysis

(a)
 (b)

Figure 2: representative pedigree analysis of (a) autosomal dominant trait (for

example: myotonic dystrophy) (b) autosomal recessive trait (for example: sickle-
cell anemia)

Genetic Disorder:

These are disorders or illness caused by one or more abnormalities in the

autosomes or sex chromosomes of the person. Thus, these are referred to as
autosomal disorders or sex-linked disorders, respectively
figure 3: meiosis
mistakes which
cause several
disorders.
(I)Mendelian Disorder:

These are mainly determined by alternation or mutation in a gene. The

chromosome number remains constant. These are transmitted to next generation
according to the principle of inheritance and can be studied with the help of
pedigree analysis. These can be dominant or recessive, as follows:-

(i)Autosomal Dominant: e.g.: Huntington disease, myotonic dystrophy, etc.

(ii)Autosomal Recessive: e.g.: Cystic fibrosis, thalassemia.

(iii)Sex-linked Dominant: e.g.: defective tooth enamel.

(iv)Sex-linked Recessive: e.g.: colour blindness, haemophilia, etc.

The pattern of inheritance of autosomal recessive trait is shown in the given figure
4.

(II) Chromosomal Disorders:

These are caused due to absence or excess or abnormal arrangement of one or
more chromosomes.

Failure of segregation of chromatids during cell divisions cycle results in the gain
or loss of chromosomes called aneuploidy. For e.g. Down’s syndrome and
Turner’s syndrome.

Failure of cytokinesis after TELOPHASE stage of cell division results in an

increase in a whole set of chromosomes in an organism, and this phenomenon is
called as polyploidy. This condition is often seen in plants.

The total number of chromosomes in a normal human cell is 46 (23 pairs). Out of
these 22 pairs are autosomes and one pair of chromosomes are sex chromosomes.
Sometimes, though rarely, either an additional copy of a chromosome may be
individual or an individual may lacks of any one pair of chromosomes. These
situations are known as trisomy or monosomy of a chromosome respectively. Such
a situation leads to very serious consequences in the individual. Down’s syndrome,
Turner’s syndrome, Klinefelter’s syndrome are common examples of chromosomal
disorders.

WHAT IS DOWN’S SYNDROME?

Down’s syndrome, also known as trisomy 21, is caused by the presence of all part
of a 3rd copy of chromosome 21. It is named after John Langdon Down, the British
physician who described the syndrome first time in 1866. In 1866, he wrote a
paper entitled “Observations on the ethnic classifications of Idiots” in which he put
forward the theory that it was possible to classify different types of conditions by
ethnic characteristics. He listed several types including the ethopian type. He is the
most famous of his classification of what is known as Down’s syndrome named
after him, but which he classified as the Mongolian type of Idiot. As a result,
Down’s syndrome was also known as “Mongolism” and people with Down’s
syndrome referred to as “Mongoloids” but the use of the “Mongolism” is now
stopped after having so many criticisms about referring racist title. Thus, Down’s
syndrome occurs in all human population, and analogous conditions have been
found in other species showing symptoms as a chimpanzees.

The chromosome aberration was discovered in 1959 by the French human

GENETICIST Jérôme Jean Louis Marie Lejeune (1926-1994). He discovered
that Down’s syndrome was caused by an extra chromosome on 21st pair. The
French Academy Of Science published his scientific work on January 26, 1959.
For the first time in the world history, his discovery established a link between an
intellectual disability of chromosomal abnormalities.
GENETIC BACKGROUND:

Down’s syndrome is a complex set of pathologies caused by an extra copy of

human chromosome 21 (HSa 21). Down’s syndrome occurs in about one in 750
lives births, cause learning difficulties.

KARYOTYPE OF DOWN’S SYNDROME:

Trisomy 21 (47,XY,+21) is caused by a meiotic non- disjunction event. A

typical gamete (either egg or sperm) has one copy of each chromosome (23 total).
When it is combined with a gamete from the other parent during conception, the
child has 46 chromosomes. However, with non-disjunction, a gamete is produced
with an extra copy of chromosome 21 (the gamete has 24 chromosomes). When
combined with a typical gamete from the other parent, the child now has 47
chromosomes, with three copies of chromosome 21. The trisomy 21 karyotype
figure shows the chromosomal arrangement, with the prominent extra chromosome
21.

Trisomy 21 is the cause of approximately 95% of observed Down syndrome, with

88% coming from non-disjunction in the maternal gamete and 8% coming from
non-disjunction in the paternal gamete. Mitotic non-disjunction after conception
would lead to mosaicism, and is discussed later.

Some cases have been reported of people with Down syndrome having children
with trisomy 21. In these cases (all from mothers), the ovaries were trisomy 21,
leading to a secondary non-disjunction during gametogenesis and a gamete with an
extra chromosome 21. Such Down syndrome trisomies are indistinguishable from
Down syndrome trisomy created through meiotic non-disjunction.
-figure 5: Karyotype of down’s syndrome.

Signs and symptoms:

1) Fatal nose bridge.

2) Slanted eyes that point upward.
3) Short neck.
4) Small ears, hands and feet.
5) Weak muscle tone at birth.
6) Small pinky fingers that points inward towards the thumb.
7) Shorter than average height.
8) One crease in the palm of their hand (PALMER CREASE).

CURRENT SCENARIO:

ALL OVER THE WORLD:

Down’s syndrome is the most common chromosomal condition diagnosed in US.

Each year about 5700 babies born in the US have Down’s syndrome.

IN INDIA:
Down’s syndrome affects approximately 23000-28000 children born in India every
year. Through the number are alarming, there is very little open dialogue on this
topic in India. Though it is not fatal in develop countries but in India it continues to
be fatal.

CONCLUSION:

Many children with Down’s syndrome who have received family support, special
therapy and education manage to graduate from High Schools and are able to do
paid work and some participated in post-secondary education as well. Early
childhood intervention, screening and vocation training can improve the overall
development of children with Down’s syndrome. As individuals with Down’s
Syndrome continue to experience longer lives the need to understand their aging
and associated health conditions becomes more crucial. Education and proper care
will improve quality of life significantly, despite genetic limitations. Especially,
adults with Down’s syndrome should be provided with appropriate information to
better understand, and counseling to cope with changes in their own level of ability
or health.

(II) WHAT DO YOU KNOW ABOUT TURNER’S SYNDROME?

Turner’s syndrome also referred to as congenital ovarian hypoplasia syndrome,

was first described by HENRI TURNER, an Olklahoma physician in 1938. It is the
most common sex chromosomal abnormality found in females. It results when one
of the X-chromosome is missing, partially or completely deleted.

Turner’s syndrome results from a deletion or the non-funtioning of one X-

chromosome in females. About half of the population with Turner’s syndrome
have monosomy X(45, X0). The other 50% of the population has a Mosaic
chromosomal component (45, X with mosaicism).
CAUSES:

1) Monosomy: where the X-chromosome is completely absent and only X-

chromosome is present.
2) Mosaicism: here, an error occur in cell division due to which a chromosome
pair contains two copies of ‘X’ and one pair does not have two copies, a
single X-chromosome is present.
3) X-chromosome change: some changes occurs in any of the parts of X-
chromosome due to which it is malfunctioning.
4) Y-chromosomal material: some presence of Y-chromosome, due to which a
female seems like a male which is known as GONADOBLASMA.

-figure 6: Karyotype of Turner’s syndrome.

Normally, during reproduction, a sperm with 23 chromosomes fertrilises an egg
with 23 chromosomes resulting in complete set of 46 chromosomes, half from the
father and other half from the mother. Sometimes, an error occurs when an egg or
sperm cell is forming, causing it to have a missing or abnormal sex chromosome.
Turner’s syndrome occurs when either the egg or sperm fails to contribute as a
normal sex chromosome to the embryo, resulting in all or part of one of the
chromosomes being missing. In some cases, the embryo may initially contain 46
chromosomes however, shortly after conception, the sex chromosomes do not
divide properly, leaving a set cells with only X-chromosome.

→About 50% of Turner’s syndrome results from missing an entire X-chromosome.

→About one-third of girls with Turner’s syndrome have the normal number of
chromosomes (46 total), but they are missing a portion of second X-chromosome.
In some cases, this is because the ends of the chromosomes join together forming a
ring, in other cases, the chromosomes may be made up of two copies of the long
(q) arm, and be missing the short or (p) arm. This is called isochromosomal
condition due to the presence of isochromosome.

When only part of a X-chromosome is missing (called a deletion) the features of

Turner’s syndrome that are present may vary depending upon which part of the X-
chromosome is missing. Often, girls with Turner’s syndrome have mosaic pattern (
two or more chromosome patterns in cells).

SYMPTOMS AND SIGNS:

It resulting in short stature of and lack of puberty, along with several other medical
issues. The severity of these problems varies among affected individuals.
Typically, a female has two X-chromosomes. Turner’s syndrome occurs in 1 in
2000- 2500 females.

RELATED MEDICAL ISSUES:

1) Short stature: Girls with only 4 feet and 5 inches height.

2) Absence of puberty: Poorly formed or absence of some parts of ovaries.
3) A particularly short, wide neck (webbed neck).
4) A broad chest and widely spaced nipples
5) Arms with small spoon shaped nails.
6) A low hairline.
7) Teeth problems.
 8) A large number of moles.
9) A short fourth finger in hand or toe.
10)Arms that turn out slightly at the elders.

CURRENT SCENARIO :

All over the world:

Turner’s syndrome affects of every 2000-2500 females live birth worldwide. This
order affects all races and regions of the world equally. There are no known
environment risks for Turner’s syndrome. US has highest number, i.e., more than
70,000 females.

In India:

Based on a number of cytogenetic studies the incidence of Turner’s syndrome is

estimated to range from 25-210 per 100,000 women.

It is best to consult a doctor before pregnancy.

CONCLUSION:

Turner’s syndrome can cause a variety of medical and developmental problem,

including short height, failure of the ovaries to develop and heart defect. So,
Government must take some necessary steps for their education and future.

What is Klinfelter’s syndrome ?

The term “klinfelter’s syndrome”, describes a set of features that can occur in a
male who is born with an extra X-chromosome in his cells. It is named after
Doctor Henry Klinfelter, who identified the condition in 1940s.

Usually every cell in a male’s body, except sperm and red blood cells, contains 46
chromosomes. The 45th and 46th chromosomes, the X and Y chromosomes are
sometimes called sex-chromosomes, because they determine a person’s sex.
Normally, males have one X and Y-chromosomes, making them XY makes with
klifelter’s syndrome have an extra X- chromosome making them XXY.

Klinefelter’s syndrome is sometimes called 47, XXY (47 refers to total

chromosomes ) are the XXY condition. These with Klinefelter’s syndrome are
sometimes calles XXY males.

Some males with klinefelter’s syndrome may have both XY cells and XXY cells in
their bodies. This is called MOSAIC. MOSAIC males may have fewer symptoms
of Klinefelter’s syndrome; depending on the number of XY cells are located. For
example, males with normal XY cells in their testis may be fertile.
Klinefelter;s syndrome is a common condition that results when a person assigned
male at birth has an extra copy of the X sex chromosome instead of the typical XY.
Klinefelter’s syndrome is a genetic condition that occurs before birth, but it often
isn't diagnosed until adulthood.

Klinefelter syndrome may affect testicular growth. This results in smaller testicles,
which can lead to making less of the hormone testosterone. The syndrome also
may cause smaller muscle mass, less body and facial hair, and extra breast tissue.
The effects of Klinefelter’s syndrome vary, and not everyone has the same
symptoms.

Most people with Klinefelter’s syndrome produce little or no sperm, but assisted
reproductive procedures may make it possible for some people with Klinefelter’s
syndrome to have biological children.

SIGNS AND SYMPTOMS OF KLINEFELTER’S SYNDROME;

 Karyotype of Klinfelter’s syndrome.

Not all boys with Klinefelter’s syndrome will have noticeable symptoms. Other
boys can have symptoms that are physically apparent or problems with speech,
learning, and development.

Babies with Klinefelter’s syndrome typically have weak muscles, reduced strength,
and quiet personalities. They also can take longer to do things like sit up, crawl,
walk, and speak.

Compared with other kids their age, boys with Klinefelter’s syndrome might have
some or all of these symptoms:

 a taller, less muscular body

 broader hips and longer legs and arms
 larger breasts (a condition called gynecomastia)
 weaker bones
 a lower energy level
  smaller penis and testicles
 delayed or incomplete puberty (some boys won't go through puberty at all)
 less facial and body hair following puberty.

To diagnose Klinefelter syndrome, a healthcare professional does a physical exam and

asks questions about symptoms and health. This may include looking at the genital area
and chest and talking about development and functioning.

Main tests used to diagnose Klinefelter syndrome are:

 Hormone testing. Blood tests can show hormone level changes that are a sign of
Klinefelter syndrome.
 Chromosome analysis. Also called a karyotype, this test can confirm a diagnosis
of Klinefelter syndrome. A blood sample is sent to the lab to check the shape and
number of chromosomes.

WHEN TO CONSULT A DOCYOR?

Healthcare professionals sometimes diagnose Klinefelter’s syndrome before birth

when testing is done for another reason. The syndrome can be found in pregnancy
during a procedure to look at fetal cells taken from the fluid around the baby or
from the placenta. These tests may be done for pregnant people who are older than
age 35 or have a family history of genetic conditions.

Klinefelter’s syndrome may be suspected during a noninvasive prenatal screening

blood test. This test looks at cell-free DNA in the pregnant person's blood sample.
To confirm the diagnosis, more-invasive prenatal testing is needed.

TREATMENT;

If you or your child is diagnosed with Klinefelter syndrome, your healthcare team
may include a doctor called an endocrinologist who specializes in conditions
involving the body's glands and hormones. Your team also may include a speech
therapist, a pediatrician, a physical therapist, a genetic counselor, a reproductive
medicine or infertility specialist, and a counselor or psychologist.

Although there's no way to repair the sex chromosome changes due to Klinefelter
syndrome, treatments can help lessen its effects. The earlier the condition is
diagnosed and treatment is started, the greater the benefits. But it's never too late to
get help.

Treatment for Klinefelter’s syndrome is based on symptoms and may include:

 Testosterone therapy. Starting at the time of the usual onset of puberty,
testosterone therapy can be given to help stimulate changes that typically
occur at puberty. These changes include a deeper voice, facial and body hair,
bigger muscle mass, and sexual desire. Testosterone therapy also can help
bone density. It may help mood, focus and attention too. Testosterone therapy
does not help with fertility problems.
 Breast tissue removal. If extra breast tissues develops, the tissue can be
removed by a plastic surgeon, if desired.
 Therapy. Speech and language therapy can help if there are speech or
language problems. Physical therapy can help with motor skills and muscle
strength. Occupational therapy can help with social skills and job skills.
 Educational evaluation and support. If learning and socializing are a
problem, extra services may help. Talk to your child's teacher, school
counselor or school nurse about what kind of support is available.

 Fertility treatment. Most people with Klinefelter syndrome cannot have

biological children because few or no sperm are made in the testicles. For
some people who make a small amount of sperm, a procedure called
intracytoplasmic sperm injection (ICSI) may help. During ICSI, sperm is
taken from the testicle with a biopsy needle and injected directly into the egg.
 Mental health support. Having Klinefelter syndrome can be a challenge,
especially during puberty and young adulthood. Coping with infertility also
can be a challenge. A family therapist, counselor or psychologist can help
work through emotional concerns.

GENERAL TREND;

ALL OVER THE WORLD;

Klinefelter’s syndrome affects about 1 in 650 who were assigned male at

birth. It is the most common sex chromosome disorder which traps all over the
world.

IN INDIA;

Klinefelter’s syndrome is the commonest aneuploidy syndrome which occurs

in about 150 per 1,00,000 males.
CONCLUSION:

People with Klinefelter’s syndrome often have less testosterone than those
without the condition. Some won’t start puberty at all, while others will start
but then stop or regress. This happens because the testicles usually fails in
Klinefelter’s syndrome, which makes them unable to make testosterone and
sperm.

EDWARD’S SYNDROME:

It was described by Edward in 1960. This syndrome is due to an extrea

chromosome number 18. Thus total number of chromosome is 47. It occurs
more often in females than in males. The frequency of this abnormality is
about 1 per 8000 live births. The affected person keep the fingers tightly
clenched against the palm of the hand. Other symptoms are small jaws,
deformed ears, small mouth, nose and fingers, small sternum and pelvis. The
patient is mental retarted and dies within six months after birth.
PATAU,S SYNDROME:

It was described by Patau in 1960. This syndrome is due to an extra

chromosome number 13. The affected person has bsmall head and
abnormalities of the face, eyes and forebrain, cleft lip and palete, low set
deformed ears, small chin and the hands are often clinched in the manner
described for Edward’s syndrome. It occurs about 1 in 20,000 live births. The
average lifespan of the affected person is about 4 months.

CRI DU CHAT (CAT CRY) SYNDROME:

The affected newborn cries like mewing of the cat. It was first described by
Lejeune in 1963 in France. Hence it is named as CRI DU CHAT (cat cry).
The condition is due to deletion of half part in the short arm of the
chromosome number 5. It is very rare. The affected person has a small head,
widely spaced eyes, moon like face, cry like kitten, receding chin and
congenital heart disease.

MYELOGENOUS LEUKEMIA:

It is caused by deletion of some portion of long arm of chromosome 22 and

its addition to chromosome 9 ( reciprocal translocation ). It brings about
change in the conformation of C-Abl protein and activates latent oncogenic
potential causing production of excess of granular leucocytes, and hence
called chronic granulytic leukemia or chronic myloid leukemia (CML). This
22nd chromosome whose a little segment form a long arm is deleted, is called
Philadelphia chromosome as it was first reported in the city of Philadelphia in
1959.

SUPERFEMALES (poly X female syndrome):

Such individuals have 47 (44+XXX, triplo-X), 48(44+XXXX) or

49(44+XXXXX) chromosomes. These females are characterized by abnormal
sexual development and mental retardation. The number of barrbodies are one
less than total number of X-chromosomes. The frequency at birth of 44+XXX
is 1 in 1500. The symptoms are more severe with the increase in number of X-
chromosomes. Such females are taller with normal fertility.

SUPERMALES (poly Y male syndrome):

 Such individual have 47(44+XYY) chromosomes. These males are
characterized by abnaormal height, mental retardation, antisocial and criminal
bent of mind (criminal syndrome or Jacob’s syndrome). There are an over
production of male sex hormones. Supermales are more aggressive than
normal males. Its frequency is 1 in 1000. Such males are taller with 1Q 80-
120. There are normal in sexual function, fertility and genitalia.]

CONCLUSION OF CHROMOSOMAL DISORDER;

Although there is no specific type of treatment to ultimately a hormone test

used to check to cure a child with this syndrome, there are many ways and
treatments to minimize the effects.
1. Testosterone replacement therapy- This is one of the most common types of
therapy to cure this syndrome. This therapy, although it does not improve
infertility but helps in stimulating different types of physical changes in puberty.
2. Plastic surgery: This method can be used in reducing breast tissue sizes.
3. Educational and support services: This type of support helps the affected with
Speech and physical therapy and helps them improve their social skills.

Although curing chromosomal disorders is not easy, it is never too late to do

treatments to minimize the effects. Both the two syndromes included in this article
are caused due to an addition of an X-chromosome. However, many such
abnormalities occur due to the deletion or addition of chromosomes.

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