chromosomal disorders
is a result of a missing, extra, or irregular portion of chromosomal DNA. It can be from an abnormal number of chromosomes or a structural defect in one or more chromosomes.
Chromosomal anomaly or disorder
Chromosomal anomaly or disorder is a result of a missing, extra, or irregular portion of chromosomal DNA. It can be from an ____________ of chromosomes or a _______ in one or more chromosomes.
-abnormal number
-structural defect
Two main groups of Chromosomal Disorders:
1. Numerical disorder
2. Structural disorder
It occurs when an individual is missing either a chromosome from a pair (monosomy) or has an extra or more than two chromosomes of a pair (trisomy, tetrasomy, etc.).In humans an example of a condition caused by a numerical anomaly is Down Syndrome also known as Trisomy 21 (an individual with Down Syndrome has three copies of chromosome 21, rather than two). An example of monosomy is Turner Syndrome,
where the individual is born with only one sex chromosome, an X.
Numerical disorder
Numerical disorder
It occurs when an individual is _____ either a chromosome from a pair (monosomy) or has an _____ or more than two chromosomes of a pair (trisomy, tetrasomy, etc.). In humans an example of a condition caused by a numerical anomaly is Down Syndrome also known as Trisomy 21 (an individual with Down Syndrome has three copies of chromosome 21, rather than two). An example of monosomy is Turner Syndrome,
where the individual is born with only one sex chromosome, an X.
missing
extra
example of a condition caused by a numerical anomaly:
Down Syndrome also known as Trisomy 21
Turner Syndrome example of monosomy
When the chromosome's structure is altered
Structural disorder
Structural disorder
When the chromosome's structure is altered, this can take several forms:
-deletions
-duplications
-inversions
-inserions
-translocations
A portion of the chromosome is missing or deleted
deletions
A portion of the chromosome is duplicated, resulting in extra genetic material.
Duplications
A portion of the chromosome has broken off, turned upside down and reattached, therefore the genetic material is inverted.
Inversions
A portion of one chromosome has been deleted from its normal place and inserted into another chromosome.
Insertions
A portion of one chromosome is transferred to another chromosome.
Translocations
Examples of common chromosomal disorder in humans:
1. Chat DuChat Syndrome
2. Klinefelter Syndrome
3. Turner Syndrome
4. Super Male Syndrome or Jacobs Syndrome
5. Down Syndrome
6. Edwards Syndrome
7. Patau Syndrome
8. Prader-Willi Syndrome
9. Angelman Syndrome
10. Fragile X Syndrome
("Cry of the cat") caused by missing portions chromosome 5.
Primarily Affects: Both males and females, with females having a slightly higher frequency.
Symptoms: Symptoms of Cri Du Chat Syndrome include a high pitched cry in infants which is similar to that of cats, mental retardation, small head, small jaw, low birth weight, slow growth, abnormally shaped or low-set ears, slow or incomplete development of motor skills, wide set eyes, webbing or fusing of fingers or toes, downward slanted eyes, low muscle tone, separated abdominal muscles, etc.
Key Statistics: Relatively rare genetic condition; estimated incidence of between around 1:25,000 to 1:50,000 births
Cri Du Chat Syndrome
Cause: Males with _________receive an extra X chromosome, thus giving them 47 rather than the normal 46 chromosomes (an extra sex chromosome).
Primarily Affects: Males. It is the most common sex chromosome disorder in males.
Symptoms: Reduced fertility, neurophysiological impairments in terms of execution, smaller
testicles, gynecomastia (increased breast tissue), rounded body, etc.
Key Statistics:47XXY, the most common of the sex chromosome variations, is said to occur in 1 out of 500 males.
Thousands of 47XXY individuals in the United States alone. Many remain undiagnosed.
Klinefelter's Syndrome
caused by the absence of entire X chromosome for females.
Primarily Affects: Females
Symptoms: Low-set ears, webbed neck, broad chest, non-working ovaries, hypothyroidism, diabetes, vision problems, neuro/cognitive deficiency, congenital heart disease, etc.
Key Statistics: Turner's Syndrome occurs in approximately 1 of every 2,000 female births and in as many as 10% of all miscarriages.
Turner's Syndrome
Cause: Male receives an extra Y chromosome from his father. (a.k.a. XYY Syndrome)
Symptoms: Physical features : increased belly fat, a large head (macrocephaly), unusually large teeth (macrodontia), flat feet (pes planus), fifth fingers that curve inward (clinodactyly), widely spaced eyes (ocular hypertelorism), and abnormal side-to-side curvature of the spine (scoliosis). associated with an increased risk of learning disabilities and delayed development of speech and language skills. Affected children can have delayed development of motor skills (such as sitting and walking) or weak muscle tone (hypotonia). Other signs and symptoms of this condition include hand tremors or other involuntary movements (motor tics), seizures, and asthma.
Individuals with 47,XYY syndrome have an increased risk of behavioral, social, and emotional difficulties compared with their unaffected peers. These problems include attention deficit/hyperactivity disorder (ADHD); depression; anxiety; and autism spectrum disorder, which is a group of developmental conditions that affect communication and social interaction.
These characteristics vary widely among people with this condition. Most affected individuals are not aware of their condition.
Key Statistics: occurs in about 1 out of 1000 male children.
Super Male Syndrome or Jacobs Syndrome
occurs when there is an extra copy of chromosome 21.
This form of Down syndrome is called Trisomy 21.
Primarily Affects: Equal frequency for males and females.
Symptoms: Symptoms of Down Syndrome include small ears, small mouth, upward slanting eyes, flattened nose, decreased muscle tone at birth, wide hands, delayed mental development, eye problems, hearing problems, hypothyroidism, hip problems, sleep apnea, etc.
Key Statistics: There are more than 400,000 people living with Down syndrome in the United States.
Life expectancy for people with Down syndrome has increased dramatically in recent decades - from 25 in 1983 to 60 today.
The incidence of births of children with Down syndrome increases with the age of the mother.
Down Syndrome
also known as Trisomy 18. A person has a third copy of genetic
material from chromosome number 18, instead of usual two copies.
Primarily Affects: Appears to affect females three to four times more than males.
Symptoms: Low-set ears, mental deficiency, small head, small jaw, unusually shaped chest, low birth weight, crossed legs (as a preferred position), congenital heart disease, kidney problems, cleft or hole in iris, etc.
Key Statistics: Occurs in about 1:3000 live births.
Small number of babies (<10%) live at least one year.
Edwards Syndrome
occurs when a person has three copies of genetic material from chromosome 13, instead of the usual two copies. Thus, it is also known as Trisomy 13.
Primarily Affects: Females slightly more than males, or males and females equally.
Symptoms: Cleft lip, decreased muscle tone, severe mental retardation, small eyes, small head, undescended testicles, low-set ears, seizures, close-set eyes, skeletal abnormalities, clenched hands, umbilical hernia, extra fingers or toes, etc.
Key Statistics: Occurs in approximately 1 in 10,000 live born infants.
Patau Syndrome
Cause: Seven genes are deleted or unexpressed on chromosome number 15
Primarily Affects: Equal frequency of males and females.
Symptoms: In utero: reduced movement, often-occurring abnormal fetal positions. At birth: lethargy, feeding difficulties, hypotonia. In infancy: excessive sleeping, scoliosis. In
childhood: sleep disorders, excessive weight gain, speech delay, hyperphagia (over-eating). In adolescence: delayed puberty, obesity, extreme flexibility. In adulthood: infertility, extreme flexibility, hypotonia, decreased pubic hair. Adults with Prader-Willi Syndrome also often have increased amount of central fat, narrow foreheads, almond-shaped eyes, and delayed motor development.
Key Statistics: Prevalence estimates have ranged from 1:8,000 to 1:25,000 with the most likely figure being 1:15,000.
Prader-Willi Syndrome
caused by the deletion of genetic material on maternally
inherited chromosome 15. It is often counted as a "sister disorder" to Prader-Willi Syndrome due top to occurrence in same genetic area.
Primarily Affects: Equal frequency for males and females.
Symptoms: Angelman Syndrome is a neuro-genetic disorder. Symptoms include seizures, jerky
movements, speech impairments, small head size, hyperactivity, motor difficulties, etc.
Key Statistics: Prevalence of Angelman's Syndrome among children and young adults is between 1/10,000 and 1/20,000
Angelman Syndrome
expansion of a single trinucleotide gene sequence (CGG) on the X chromosome occurs. This results in a failure to express the protein coded by the FMR1 gene.
Primarily Affects: Males more severely than females.
Researchers: Dr. Randi J. Hagerman, Dr. Paul Hagerman.
Symptoms: Mental retardation, tendency to avoid eye contact, speech and language delays, hyperactive/impulsive behavior, long face, large body size, flat feet, soft skin, oversized testes
in males who have reached puberty, large forehead or ears, prominent jaw, etc.
Key Statistics: Fragile X syndrome is the most common inherited cause of mental impairment. The syndrome occurs in approximately 1 in 3600 males and 1 in 4000 to 6000 females.
Fragile X Syndrome