Deck 6: Cytogenetics: Karyotypes and Chromosome Aberrations

Question 1

Which one of the following pairings of an aneuploidy and the syndrome it causes is incorrectly matched?

A) X-chromosome monosomy (X and no Y) causes Turner syndrome.
B) X-chromosome trisomy causes Klinefelter syndrome.
C) Trisomy 21 causes Down syndrome.
D) Trisomy 13 causes Edwards syndrome.
E) Uniparental disomy causes Prader-Willi syndrome.

Answer 1

D

Question 2

What percentage of parents decide to terminate a Down Syndrome pregnancy?

A) 10 percent
B) 30 percent
C) 50 percent
D) 70 percent
E) 90 percent

Answer 2

E

Question 3

A chromosome whose centromere is close to the end of the chromosome is called _______.

A) submetacentric
B) metacentric
C) acrocentric
D) mesocentric
E) pericentric

Answer 3

C

Question 4

How does polyploidy differ from aneuploidy?

A) Polyploidy involves diploid chromosome sets, while aneuploidy involves haploid sets.
B) Polyploidy involves changes in entire chromosome sets; aneuploidy involves less than a diploid set of chromosomes.
C) Polyploidy involves monosomy; aneuploidy involves trisomy.
D) Polyploidy is produced by translocations; aneuploidy by nondisjunction.
E) None of these is a difference between polyploidy and aneuploidy.

Question 5

When making a karyotype, what is the effect of placing lymphocytes in a low-salt solution?

A) It makes the chromosomes more visible.
B) It initiates cell division.
C) It stops the cells in metaphase.
D) It helps separate the chromosomes.
E) It causes the cells to swell.

Question 6

The placement of chromosomes into one of the seven groups in a karyotype is based on the chromosome's

A) size.
B) centromere position.
C) banding pattern.
D) size and centromere position only.
E) all of these.

Question 7

The risk for Down syndrome increases in situations where the

A) mother is 20-29 years old.
B) father is 35-50 years old.
C) mother is 35-45 years old.
D) father is 20-29 years old.
E) both parents are 30-35 years old.

Question 8

If nondisjunction takes place in one of the cells of the second meiotic division, the four products of meiosis will include

A) two normal and two abnormal karyotypes.
B) four abnormal karyotypes.
C) three normal and one abnormal karyotype.
D) four normal karyotypes.
E) none of these.

Question 9

The region at the end of a chromosome is termed the _______.

A) centromere
B) telomere
C) satellite
D) P arm
E) Q arm

Question 10

The letters G, Q, R, and C are used to describe bands that appear on chromosomes. The letters refer to

A) the position of the bands.
B) the staining procedure used to reveal the bands.
C) the size of the bands.
D) the types of genes found within the bands.
E) the relative importance of the bands in karyotyping.

Question 11

Characterize the frequency of changes in chromosome number in humans.

A) Close to half of all conceptions are aneuploid.
B) They are a major cause of reproductive failure.
C) The frequency is significantly higher than it is in closely-related animals.
D) All of these.
E) None of these.

Question 12

Studies on aneuploidies of the sex chromosomes reveal that

A) the X chromosome is not necessary for survival.
B) the Y chromosome is not necessary for survival.
C) two copies of the X chromosome are necessary for survival.
D) two copies of the Y chromosome are fatal.
E) none of these is true.

Question 13

Most triploid zygotes arise from

A) fertilization of a diploid egg by a normal haploid sperm.
B) fertilization of a normal haploid egg by a diploid sperm.
C) fertilization of a normal haploid egg by two sperm.
D) nondisjunction during the zygote's first mitotic division.
E) fusion of the zygote with an unfertilized egg.

Question 14

Chromosome painting is a relatively new technique in karyotype analysis. Which one of the following statements about chromosome painting is false?

A) It is done to make abnormalities easier to detect.
B) The dyes used to create color are fluorescent dyes.
C) The dyes are attached to DNA sequences.
D) In a normal karyotype, each chromosome appears with bands of different colors.
E) Each of the 24 different chromosome types has a unique appearance.

Question 15

The two most common types of polyploidy in humans are

A) trisomy and aneuploidy.
B) triploidy and haploidy.
C) triploidy and tetraploidy.
D) tetraploidy and diploidy.
E) haploidy and diploidy.

Question 16

Amniocentesis and chorionic villus sampling are two methods of prenatal diagnosis. One important difference between these techniques is that

A) chorionic villus sampling is more routinely prescribed.
B) amniocentesis can diagnose chromosome disorders, while chorionic villus sampling cannot.
C) chorionic villus sampling can be performed earlier than amniocentesis.
D) maternal risks are higher with chorionic villus sampling.
E) the risk of miscarriage is higher with amniocentesis than with chorionic villus sampling.

Question 17

Which of the following is not information derived from karyotypes?

A) The number of chromosomes in a genome.
B) The number and type of sex chromosomes.
C) The presence or absence of individual chromosomes.
D) Structural abnormalities.
E) The pattern of inheritance: recessive, dominant, etc.

Question 18

A translocation involving chromosome 21 can result in

A) a risk for Down syndrome independent of maternal age.
B) a risk for Down syndrome dependent on paternal age.
C) no increased risk outside of maternal age.
D) lowering the risk of Down syndrome.
E) no change in the risk for Down syndrome.

Question 19

The region that divides a chromosome into two arms is the ______.

A) centriole
B) centromere
C) chromatin
D) chromatid
E) centrum

Question 20

Fragile sites are chromosome locations that

A) show an increased number of chromosome bands.
B) show a decreased number of chromosome bands.
C) are all associated with a specific defective phenotype.
D) indicate that carriers are mentally retarded.
E) are inherited in a codominant fashion.

Question 21

The short arm of a submetacentric chromosome is symbolized as the ____________________ arm.

Question 22

Amniocentesis is typically not perfomed on mothers over the age of 35.

Question 23

Klinefelter syndrome patients who are mosaics have some cells with 46, XY and others with ____________________.

Question 24

The degree of mental retardation in a Down syndrome fetus is predictable.

Question 25

_______ describes a chromosome that has a centrally-placed centromere.

Question 26

What is the number of chromosomes in a human tetraploid cell? ____________________

Question 27

What would be the karyotypic designation of a female with trisomy for the X chromosome? ____________________

Question 28

Due to a chromosome deletion, Timothy is very retarded, both physically and mentally. He also has a severe abnormality of his voice-box so that his cry is abnormal. Give the karyotypic designation and the name of the syndrome that he most likely has. ____________________

Question 29

If a mother already has a child with chromosomal abnormalities, the risk of having another child with chromosomal abnormalities is 10 percent.

Question 30

The reason for the spontaneous abortion of almost all 45, X fetuses is unknown.

Question 31

The banding patterns are different for non-homologous chromosomes.

Question 32

Monosomy for autosomes is lethal in humans. If an aborted male fetus had monosomy for chromosome 6, how would you designate (write) the karyotype? ____________________

Question 33

Turner syndrome is associated with severe mental retardation.

Question 34

Which of the following is an enzyme used in G-banding?

A) Quinacrine
B) Giemsa
C) Trypsin
D) Catalase
E) Peroxidase

Question 35

The most common survival trisomy is trisomy 13.

Question 36

The most common sex chromosome abnormality found in spontaneous abortions is 45, X.

Question 37

The pattern of G-bands on each member of a homologous pair of chromosomes is usually different.

Question 38

How many chromosomes are in a red blood cell taken from a normal person? ____________________

Question 39

The effect of colcemid on cells is to stop division at anaphase.

Question 40

In this type of prenatal diagnosis, karyotype analysis can be performed as early as 8 weeks.

A) Amniocentesis
B) Chorionic villus sampling
C) Cell-free fetal DNA analysis
D) Pre-genetic diagnosis
E) Polyploid analysis

Question 41

Describe the chromosomal constitution of the four cells of meiosis if a nondisjunction event occurred in Anaphase II.

Question 42

Describe chromosomal deletions, inversions, and translocations. If an individual had an inversion on chromosome 12 and another had a deletion on chromosome 12, which would be more affected and why?

Question 43

Nondisjunction of the sex chromosomes produces both Klinefelter syndrome (XXY) and Turner syndrome (XO), but among live births, 1 in 1,000 males is XXY, but only 1 in 10,000 females is XO. What mechanisms can account for this tenfold difference in frequency?

Question 44

What chromosomal mutation occurs in each of the following: Patau syndrome, Klinefelter syndrome, Turner syndrome, and Angelman syndrome?

Question 45

People with the chromosome constitution ____________________ were once considered more genetically predisposed to committing violent crime than those with a normal chromosome constitution.

Question 46

In general, how do sex chromosome aneuploidies differ from autosomal aneuploidies?

Question 47

Distinguish between:
a. Trisomy 13 and trisomy 18
b. Triploidy and tetraploidy
c. Angelman syndrome and Prader-Willi syndrome

Question 48

A chromosome whose centromere is near one end is termed ____________________.

Question 49

In the case of nondisjunction producing a trisomic condition, how might it be possible to determine in which parent this event occurred? Might it be possible to determine whether this event occurred in the first or second meiotic division?

Question 50

A balanced chromosome complement is necessary for normal development, with adverse consequences for additional or missing chromosomes or chromosome fragments. Use examples to show which is more harmful to the individual.

Question 51

Cell-free fetal DNA originates from the breakdown of fetal cells in the __________.

Question 52

The most precise prenatal diagnosis for detecting chromosomal abnormalities is __________.

Question 53

Who are translocation carriers and in what sense are they high-risk individuals?

Question 54

Figure 6.21 shows identical twins who differ in their sex chromosome constitution. How could this condition arise?

Question 55

Show how the frequencies of many chromosome abnormalities are different in newborns than they are in fetuses.

Question 56

Comment on the following statement: "Since monosomy (2n-1) for autosomes is lethal, no individuals with 45 chromosomes, including a normal pair of sex chromosomes, exist."

Question 57

Among abnormalities of the sex chromosomes, no cases of OY individuals are known, although XO individuals have been found. Why do you think this is the case? Is this evidence for differences in genetic content between the X and Y chromosome?

Question 58

Describe the chromosomal constitution of the four cells of meiosis if a nondisjunction event occurred in Anaphase I.

Question 59

Two sets of parents who have children with Down syndrome meet at a clinic. The Williams know that their son has trisomy 21. The Millers have two affected children and Mrs. Miller has had two miscarriages. Why should the Millers be more concerned about future reproductive problems than the Williams? How did Down syndrome occur in each of these families?