Molecular Biology
P. Edgerton
Name _______________________________
Block _______ Date ____________________
HUMAN CHROMOSOMAL ABNORMALITIES:
An Introduction to Common Gross Defects of Human Chromosomes
Click on “Human Chromosomal Abnormalities web activity” link. This will open up a tutorial with five
topics that will help you understand how chromosomal abnormalities are detected prenatally, what
types of genetic disorders these abnormalities cause, and how the inheritance patterns for genetic
disorders can be recognized.
Overview – Carefully read the information provided, and answer the questions below.
_____ 1.The likelihood of a child being born with a major genetic defect, such as mental retardation,
can often be detected by sampling:
A. the mother's uterus cells.
B. cells from the embryo or fetus C. the father's blood cells
_____ 2. Which of the following can be detected now by examining a karyotype?
A. over 3,000 genetic defects
B. an unborn child's gender or sex
C. both of the above
_____ 3. If there is a family history of genetic disorders, knowing the gender of an unborn child can be
important because:
A. male children are more likely to have autosomal defects show up in their phenotypes
B. female children are more likely to have autosomal defects show up in their phenotypes
C. male children are more likely to have X-linked traits show up in their phenotype
D. Both A and C
_____ 4. Most genetic disorders are due to:
A. gross chromosomal abnormalities such as irregular shapes or numbers of chromosomes
B. the gender of an individual
C. neither of the above
_____ 5. Which of the following statements is true regarding karyotype analysis?
A. It is rarely done on the cells of unborn children because it cannot detect most genetic
disorders.
B. It is now an important medical tool used in predicting the likelihood that an unborn child
will be normal.
C. It is not done any more because human pregnancy has only a small risk of birth defects.
Detection – Carefully read the information provided, and answer the questions below.
_____ 1. Karyotyping can be done from:
A. any cell in your body
B. only sex cells
C. only embryonic or fetal cells
_____ 2. Amniocentesis, chorionic villi sampling, and alpha-feto protein sampling are done to
determine:
A. the likely date of birth
B. whether or not the baby will be normal or abnormal
C. whether or not the mother has a genetic defect
D. Both A and B
_____ 3. Amniocentesis involves sampling:
A. the liquid immediately surrounding a fetus
B. the amnion
C. the placenta
_____ 4. Results of amniocentesis tests usually come back from the laboratory in:
A. 1 day or less
B. 1-2 days
C. 3-4 weeks
_____ 5. Amniocentesis usually is not done before the __________ week after conception.
A. 4th - 5th
B. 10th – 12th
C. 15th - 16th
_____ 6. Which of the following procedures has the lowest risk for an unborn child?
A. amniocentesis
B. chorionic villi sampling
C. alpha-feto protein screening
_____ 7. Amniocentesis can be used to determine whether or not an unborn child will:
A. have diabetes
C. be obese
B. have Down syndrome
D. all of these can be determined.
_____ 8. A chorion is:
A. a sack within a pregnant woman's uterus containing the amniotic fluid that surrounds a
fetus
B. a membrane that develops around an embryo and contributes to the formation of the
placenta
C. an organ in the uterus that is connected to a fetus by the umbilical cord
_____ 9. Which of the following procedures usually involves inserting a small flexible plastic tube
through the vagina into the uterus?
A. amniocentesis
B. chorionic villi sampling
C. alpha-feto protein screening
_____ 10. Which of the following diagnostic procedures is more commonly used in North America
today?
A. amniocentesis
B. chorionic villi sampling
C. alpha-feto protein screening
_____ 11. Compared to amniocentesis and chorionic villi sampling, alpha-feto protein screening is
_______________ in detecting chromosomal abnormalities.
A. more reliable
B. about equally reliable
C. less reliable
_____ 12. AFP screening can incorrectly produce results indicating that a fetus has genetic defects if:
A. the date of conception has been miscalculated
B. the mother is anemic
C. the mother has Rh negative blood
_____ 13. Alpha-feto protein is a substance normally produced by:
A. the mother
B. the fetus
Common Abnormalities – Carefully read the information provided, and answer the questions below.
_____ 1. It is likely that as many as __________ newborn infants inherits a chromosomal abnormality.
A. 1 in 5
B. 1 in 57
C. 1 in 118
D. 1 in 100,000
_____ 2. There are two major categories of inherited chromosomal abnormalities: 1) irregular
numbers of chromosomes and 2) structural modification in a chromosome. Both are usually a
result of:
A. mechanical errors during meiosis
B. mechanical errors during mitosis
C. neither of the above
_____ 3. If a child had a karyotype that had 23 + 23 + 23 chromosomes or 23 + 24, it would be:
A. within the range of normal
B. an irregular number of chromosomes
C. a structural modification in the chromosomes
_____ 4. A structural modification of a chromosome might be:
A. a break in a chromatid arm and its separation from its chromosome
B. a miscarriage or spontaneous abortion
C. a karyotype
_____ 5. What can cause a gross chromosomal modification?
A. masturbation
B. excessive frequency of sexual intercourse
C. environmental agents such as radiation
_____ 6. Inherited chromosomal abnormalities usually result from:
A. defective sperm or ova
B. a failure of the mother's uterus and placenta in carrying a fetus to full term
C. inadequate nutrition and medical care during early infancy
_____ 7. When only some of an individual's cells have a chromosomal abnormality, it is referred to as:
A. crossing-over
B. mosaicism
C. nondisjunction
Autosomal Abnormalities – Carefully read the information provided, and answer the questions.
_____ 1. Compared to sex chromosome abnormalities, autosomal ones are:
A. less common
B. more common
C. about equally common
_____ 2. Down syndrome is due to an abnormality of chromosome pair number:
A. 3
B. 11
C. 21
_____ 3. Which of the following is characteristic of people with Down syndrome?
A. They are all severely mentally retarded--they have a mental age level of a 3-7 year old
normal child
B. They frequently have other related medical problems.
C. They have a longer expected life span than average.
_____ 4. An epicanthic fold is.
A. a fold of skin over the inner corner of each eyelid that causes the eyes to have a "slanted"
Appearance
B. a large ridged tongue that rolls over a protruding lower lip
C. neither of the above
_____ 5. Which of the following types of chromosomal abnormalities are most commonly associated
with Down syndrome?
A. translocation
B. trisomy
C. mosaicism
_____ 6. Recent data suggest that by age 35, nearly 100% of people with Down syndrome develop:
A. Alzheimer syndrome
B. increased fertility
C. fragile-X syndrome
_____ 7. The risk of giving birth to a Down syndrome child ____________ with the age of the mother.
A. increases
B. decreases
C. does not change
_____ 8. Which of the following statements is true regarding Down syndrome?
A. It is the most common cause of mental retardation in North America.
B. There is no connection between the age of a father and the likelihood that his child will
inherit Down syndrome.
C. Amniocentesis is now usually recommended for women 35 and over because of their
significantly higher risk of giving birth to a Down syndrome child.
_____ 9. Which of the following statements about Down syndrome is true?
A. The majority of mothers giving birth to Down syndrome children are still in their 20's.
B. Women who have already had a Down syndrome child are at a lower risk of having another
child with this problem.
C. Women who have Down syndrome are at a lower risk of having Down syndrome children.
_____ 10. Which of the following statements is true?
A. Down syndrome is the only known autosomal abnormality.
B. Most men with Down syndrome are fertile.
C. In the past, Down syndrome was referred to as Mongoloidism.
Sex Chromosome Abnormalities – Carefully read the information provided, and answer the
questions.
_____ 1. Which of the following statements is true of sex chromosome abnormalities in humans?
A. They usually have mild effects and rarely are fatal.
B. Most are not gender specific
C. They cannot be diagnosed before birth.
_____ 2. Male sex chromosome abnormalities can be due to abnormal numbers of ___ chromosome.
A. the X
B. the Y
C. either the X or the Y
_____ 3. If someone only has one X chromosome and no Y chromosomes in their somatic cells, they:
A. are metafemales
B. have Turner syndrome
C. have Klinefelter syndrome
_____ 4. A chromosomal abnormality that causes a woman to be unusually short in stature (average
4'7"), to have a webbed neck, and to generally lack feminine secondary sexual characteristics
is:
A. Triple-X syndrome
B. Turner syndrome
C. XYY syndrome
_____ 5. A chromosomal abnormality that causes a man to have asexual to feminine body contours
with large breasts; small penis, testes, and prostate gland; relatively little body hair; and
sterility is:
A. Klinefelter syndrome
B. XYY syndrome
C. Richard Speck Syndrome