Chromosome Abnormalities
I. Chromosome Terms
A. _______________ – chromosomes that are ___ _________ in determining the sex (gender)
of an individual. (22 pairs of autosomes in humans
B. ___ _____________ – determine the sex of an organism
1. In humans
a. _____ is __
b. ________ is __
2. In _______ organisms the _________ and __________ vary
a. ex. Grasshopper female XX, male XO (O = absence)
b. birds – male XX, female XO
C. _____________ – having only _ chromosome of a set (1 missing)
D. __________ – having _ chromosomes of a set (1 extra)
II. Errors in Meiosis & Chromosomal Mutations
A. ___-__________ – the _________ separation of chromosomes during ________
1. Can happen in _______ _ – during separation of ____________ (like)chromosomes
2. Can happen in _______ __ – during separation of ____________ (identical chromosomes)
3. Results in either monosomy or trisomy
4. Is most common in ______ parents (especially females)
B. ________ – section of a chromosome is ___________ off completely
C. ____________ – chromosome fragment attaches to its homologous chromosome; causing it
to carry _ _______ of a certain set of genes.
D. ____________ – the chromosome piece reattaches to the original chromosome but in a
________ orientation.
E. ____________ – a piece of chromosome reattaches to a non-homologous
chromosome. Ex. A pieces from chromosome 9 is moved to chromosome 22.
III. Karyotypes
A. A karyotpe is an organized ________ of a person’s ______________.
B. In a karyotype, chromosomes are ________ and ________ by ____, from largest to smallest.
C. This arrangement helps scientists quickly ________ chromosomal ___________.
D. To make a karyotype, scientists take a picture of someone’s chromosomes (while a cell is in
mitosis), cut them out and match them up using size, banding pattern and centromere position
as guides.
IV. Chromosomal Disorders
A. __________ Disorders – disorders in which an individual has
an extra (or piece of an extra) chromosome. _ ___________)
1. Down Syndrome (Trisomy 21) – caused by the presences of
all or part on an extra 21st chromosome. It is named after John
Langdon Down, the British doctor who described it in 1866.
Individuals with the syndrome have characteristic facial features,
short stature, heart defects, susceptibilityto respiratory infection,
and mental retardation. Individuals have a shorter life span and
are prone to leukemia and Alzheimer’s disease. The incidence
of Down Syndrome can be correlated with the age of the mother.
Down Syndrome can be identified during pregnancy or at birth
and affects 1 out of every 700 live births.
2. __________ ___________ – caused by an additional copy of
chromosome 18. Individuals with the syndrome have an elfin
appearance with small nose and mouth, a receding lower jaw,
abnormal ears, and they cannot properly bend their fingers.
Individuals also suffer from severe mental retardation. It occurs
about 1 in every 10,000 live births. Most of the affected
individuals are female and 80 to 90% of them die by age 2.
3. ______ __________ – a syndrome in which a patient has an
additional chromosome 13. The extra chromosome disrupts
the normal course of development, causing the characteristic
features of Patau syndrome which are cleft palate, hair lip,
congenital heartdefects, polydactyly (extra fingers) and severe
mental retardation. Like all non-disjunction diseases the risk
of disease in the offspring increases with maternal age at
pregnancy. Patau syndrome affects aproximately 1 in 15,000
live births.
4. ____________ __________ – is a condition caused by an
extra X sex chromosome. The principal effect is small
testes development and reduced fertility. A variety of
other physical and behavioral differences and problems
are common, though severity varies and many boys and
men with the condition have few detectable symptoms.
It is the second most common extra chromosome condition
and is named after Dr. Harry Klinefelter, an endocrinologist
who first described it in 1942. The condition exists in
roughly 1 out of every 500 to 1,000 males.
5. ______ _ _________ – syndrome characterized by the
presence of an exta X chromosome in each cell of a human
female. Occurs at a frequencey of 1/1,000 female live births.
No specific abnormalities are usually associated with
this condition. The vast majority of women who have this
condition are normal mentally and physicllay and are fertile.
Most womenwith XXX who are fertile do not tend to pass the
extra X to their offspring. It is also possible to inherit 4 or
5 X’s. With each extra X, there tends to be a corresponding
increase in mental handicap, a chance of being sterile, and a
lack of secondary sex characteristics.
6. ________ _________ – A chromosome aberration which is
causesd by non-disjunction of the Y chromosome during
the second phase of meiosis giving a 47 XYY karyotype.
Occurrences is 1/1,000 live male births. Men with this
karyotype are tall and have low mental ability. Most men
with an extra Y chromosome lead normal lives, but 4% of
men in prison are XYY..
B. __________ Disorders – disorders in which an individual is missing a chromosome or part of
a chromosome.
1. ________ _________ – syndrome in which only one X
chromosomes is present. Women with Turner’s syndrome
can live normal lives, though they are unable to bear
children. The phenotype of this female includes short
stature, short broad neck, and a broad chest. Intelligence
does not seem to be affected. This can occur in about 1 per
2,700 births and is not linked to maternal age.
2. ___ __ ____ ________ – caused by the deletion of a portion
of chromosome 5. It is characterized by a cat-like-cry (in half
the infants), a small cranium, congenital hear disease, and
severe mental retardation. The incidence of this syndrome is
1/1,000,000 live births.
3. __________ ___________ – a rare neuro-genetic disorder name after a British pediatrician,
Dr. Harry Angelman, who first described the syndrome in 1965. AS is caused by a deletion or
inactivation of critical genes on the maternally inherited chromosome #15. The syndrome is
characterized by intellectual and developmental delay, speech impediment, sleep disturbance,
unstable jerky gait, seizures, hand flapping movements, frequent laughter/ smiling and a happy
demeanor. Sometimes referred to as “Puppet man syndrome” .
The sister syndrome is called ______-_____ __________, and is caused by loss of paternal
genes. Prader-Willi syndrome (PWS) is a chromosomal disorder with symptoms that include
learning difficulties, obesity and behavioral problems.