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ABGC Practice Questions and Answers 100% Pass
Under what circumstances should an infant with clinical features of Down syndrome be karyotyped?
A. Only if the parents desire more children
B. Only if the mother is younger than 35 years old
C. Only if not all of the features of Down syndrome are present
D. Only if the mother has had 3 early miscarriages
E. Always - ANSWER ✔✔-E. Always
What is the parental origin and stage of meiosis when most meiotic errors occur resulting in
chromosomal trisomy?
A. Maternal meiosis I
B. Paternal meiosis I
C. Maternal meiosis II
D. Paternal meiosis II
E. Maternal meiosis I and II are equally likely - ANSWER ✔✔-A. Maternal meiosis I
A 23-year-old woman has a baby with the karyotype 47,XY,+21. Which of the following is the correct
conclusion?
A. This woman's risk for having another baby with a chromosome abnormality is the same as other
women her age
B. Either the woman or her husband probably has a Robertsonian translocation
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C. Either the woman or her husband probably has germ line mosaicism
D. Either the woman or her husband probably carriers a balanced reciprocal translocation
E. Both members of the couple probably have normal chromosomes - ANSWER ✔✔-E. Both members of
the couple probably have normal chromosomes
Which of the following cytogenetic results listed below indicate that the child in question has Down
syndrome?
A. 47,XX,+22
B. 46,XY,t(2;21)(q13;q21)pat
C. 46,XY,+21,der(21;22)(q10;q10)
D. 45,XX,der(14;21)(q10;q10)mat
E. 46,XX.ish del(21)(q22.3q22.3)(D21S65-) - ANSWER ✔✔-C. 46,XY,+21,der(21;22)(q10;q10)
T/F The karyotype of a spontaneous abortion is more likely to be abnormal than that of a stillborn infant.
- ANSWER ✔✔-True
T/F The most common Down syndrome karyotype involves a Robertsonian translocation between
chromosomes 14 and 21 - ANSWER ✔✔-False
T/F It is possible to have the Down syndrome phenotype and have 46 chromosomes. - ANSWER ✔✔-
True
T/F Most of the mothers of babies with Down syndrome are over 35 years of age. - ANSWER ✔✔-False
An individual with 45 chromosomes and a Robertsonian translocation between both copies of
chromosome 21 can have live born children with a normal karyotype or with trisomy 21. - ANSWER ✔✔-
False
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Which of the following karyotypes, if observed in an embryo, is least likely to survive to birth?
A. 45,X
B. 47,XX,+16
C. 47,XX,+21
D. 47,XX,+18
E. mos 47,XXX/46,XX - ANSWER ✔✔-B. 47,XX,+16
Which of the following chromosome abnormalities occurs only during meiosis II?
A. 45,X
B. 47,XXX
C. 47,XXY
D. 47,XYY
E. mos 45,X/46,XX - ANSWER ✔✔-D. 47,XYY
Which fetal karyotype, detected by prenatal diagnosis, would warrant karyotyping the parents? A.
47,XXY
B. 45,X
C. 46,XX,t(1:10)(p13;q12)
D. 47,XY,+21
E. 69,XXX - ANSWER ✔✔-C. 46,XX,t(1:10)(p13;q12)
A couple who recently had a daughter with a chromosome abnormality comes for genetic counseling.
Their daughter's karyotype is 46,XX,del(3)(p25.3). Both parents are studied and their karyotypes are
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normal. The most accurate counseling is that: A. Small deletions do not usually cause severe birth defects
and mental retardation
B. Although both parents have normal karyotypes, they could still have a small increased chance of
having another child with an unbalanced karyotype due to the possibility of germ line mosaicism
C. The parental chromosome testing should be repeated since one parent should have a balanced
translocation to explain the deletion in the child
D. The proband's phenotypically normal siblings should be karyotyped to determine if they are balanced
translocation carriers
E. Because the deletion is de novo, the proband is less likely to have birth defects and mental retardation
than if it was inherited se - ANSWER ✔✔-B. Although both parents have normal karyotypes, they could
still have a small increased chance of having another child with an unbalanced karyotype due to the
possibility of germ line mosaicism
Which of the following statements is incorrect?
A. The karyotype of 47,XXX is more common than 45,X in live born infants
B. Individuals with 47,XXX are more likely to have malformations of the heart and kidneys than are those
with 45,X
C. A chromosome analysis is indicated for an adult male with infertility of unknown cause
D. The karyotype 47,XYY is not usually associated with major birth defects
E. An individual with the karyotype 48,XXXX is more likely to be mentally retarded than one with
47,XXX - ANSWER ✔✔-B. Individuals with 47,XXX are more likely to have malformations of the heart
and kidneys than are those with 45,X
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