An important advantage of FISH over conventional karyotyping is that FISH:

Needs no fluorescence microscope

Cytogenetics: banding, abnormalities and advanced methods

42 Kerala PSC Lab Technician Gr II practice questions on Cytogenetics: banding, abnormalities and advanced methods, part of Pathology. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Medium
An important advantage of FISH over conventional karyotyping is that FISH:
1. ADetects all point mutations
2. BWorks on non-dividing cells
3. CScans the whole genome at once
4. DNeeds no fluorescence microscope
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Answer: B · Works on non-dividing cells
FISH uses fluorescent DNA probes that bind to a chosen target sequence, and the signals can be counted in interphase nuclei. It therefore needs no culture or metaphases, and results come quickly, for example for trisomy 21 or BCR::ABL1. Its limit is that it shows only the regions targeted by the probes used. A karyotype surveys all the chromosomes but needs dividing cells.
- A: Point mutations are far too small for FISH; they need sequencing or PCR.
- C: FISH shows only the regions its probes target; a karyotype surveys the whole genome.
- D: FISH signals are fluorescent and need a fluorescence microscope.
Question 2 · Medium
R-banding produces a pattern that is:
1. AThe reverse of G-banding
2. BLimited to the centromeres
3. CIdentical to G-banding
4. DSeen only on the Y chromosome
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Answer: A · The reverse of G-banding
R (reverse) banding uses heat denaturation in a hot buffer before Giemsa, or certain fluorochromes. Regions that are pale with G-banding stain dark, and dark G-bands stain pale. Because chromosome ends are usually pale with G-banding, R-banding is useful for studying the ends of chromosomes. G- and Q-banding, in contrast, give essentially the same pattern.
- B: Staining of centromeric heterochromatin only is C-banding.
- C: The R-band pattern is the opposite of G, not the same.
- D: R-bands appear along every chromosome, not just the Y.
Question 3 · Easy
The Philadelphia chromosome is characteristic of which disease?
1. AHodgkin lymphoma
2. BChronic lymphocytic leukaemia
3. CChronic myeloid leukaemia
4. DAcute promyelocytic leukaemia
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Answer: C · Chronic myeloid leukaemia
The Philadelphia (Ph) chromosome is a shortened chromosome 22 formed by the translocation t(9;22)(q34;q11.2). It joins BCR on chromosome 22 to ABL1 on chromosome 9, making the BCR::ABL1 fusion gene with tyrosine kinase activity. It is found in about 95% of CML and in some acute lymphoblastic leukaemias. Acute promyelocytic leukaemia has t(15;17) instead.
- A: Hodgkin lymphoma has no characteristic Ph chromosome.
- B: CLL is a B-cell neoplasm and is not defined by the Ph chromosome.
- D: Acute promyelocytic leukaemia carries t(15;17), PML::RARA.
Question 4 · Easy
A baby born to a 41-year-old mother has Down syndrome, with 47 chromosomes in every cell counted. The most likely cause is:
1. AMeiotic non-disjunction
2. BDeletion of chromosome 21
3. CPost-zygotic mosaicism
4. DRobertsonian translocation
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Answer: A · Meiotic non-disjunction
About 95% of Down syndrome is free trisomy 21 (47,+21), caused by non-disjunction, mostly in maternal meiosis I. The risk rises with maternal age. Translocation Down syndrome has 46 chromosomes, one of them a fused 14;21 or 21;21 chromosome. Mosaicism would show a mix of normal and trisomic cells.
- B: A deletion removes material; Down syndrome is caused by an extra chromosome 21.
- C: Mosaicism would give a mix of 46- and 47-chromosome cells.
- D: A Robertsonian translocation case has 46 chromosomes, not 47.
Question 5 · Hard
A 2-year-old with Down syndrome has 46 chromosomes, one of them a fused 14;21 chromosome. The parents plan another child. The most useful next test is:
1. ARepeat the child's karyotype
2. BNone; the risk depends on age
3. CKaryotype both parents
4. DBuccal smear for Barr bodies
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Answer: C · Karyotype both parents
This is translocation Down syndrome: the child has two normal chromosomes 21 plus a third 21 joined to a 14. In some families one parent is a balanced carrier with 45 chromosomes, including the 14;21 chromosome, and a carrier has a much higher recurrence risk than maternal age predicts, especially a carrier mother. Karyotyping both parents finds a carrier and guides counselling. Repeating the child's karyotype adds nothing, and Barr bodies show only the number of X chromosomes.
- A: The child's karyotype is already clear; repeating it adds nothing.
- B: With a translocation, a carrier parent's risk is far above the age-related risk.
- D: Barr bodies show the number of X chromosomes, not translocations.
Question 6 · Easy
Which microscope is needed to examine Q-banded chromosomes?
1. APolarising microscope
2. BDark-ground microscope
3. CPhase-contrast microscope
4. DFluorescence microscope
Answer and explanation in LearnFree account
Question 7 · Medium
A girl's karyotype is 47,XXX. How many Barr bodies are expected in her buccal cells?
1. ANone
2. BTwo
3. CThree
4. DOne
Answer and explanation in LearnFree account
Question 8 · Easy
All of the following are features of Turner syndrome EXCEPT:
1. ACoarctation of aorta
2. BStreak ovaries
3. CTall stature
4. DWebbed neck
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Question 9 · Medium
What does C-banding mainly stain?
1. ANucleolar organiser regions
2. BConstitutive heterochromatin
3. CGene-rich pale G-bands
4. DTelomeres only
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Question 10 · Medium
A tall 22-year-old man has small firm testes, gynaecomastia and azoospermia. His karyotype is most likely:
1. A47,XYY
2. B46,XY
3. C45,X
4. D47,XXY
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Question 11 · Hard
A 38-year-old woman has WBC 85,000/µL with all stages of granulocytes and many basophils. Her bone marrow culture fails, giving no metaphases. Which test can still detect the Philadelphia translocation?
1. AG-banding of the failed culture
2. BBuccal smear for Barr bodies
3. CC-banding of the marrow
4. DInterphase FISH for BCR::ABL1
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Question 12 · Easy
In G-banding, chromosomes are treated with which enzyme before Giemsa staining?
1. ADiastase
2. BPepsin
3. CTrypsin
4. DHyaluronidase
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Question 13 · Easy
Edwards syndrome is trisomy of which chromosome?
1. A21
2. B18
3. C13
4. D15
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Question 14 · Hard
A 3-year-old boy has mild features of Down syndrome. His karyotype is reported as 47,XY,+21[12]/46,XY[8]. This means:
1. AMosaic trisomy 21
2. BTranslocation Down syndrome
3. CTrisomy 21 in every cell
4. DA normal male result
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Question 15 · Hard
A dual-colour, dual-fusion BCR::ABL1 FISH probe is used (ABL1 red, BCR green). An interphase cell shows one red, one green and two yellow fusion signals. This cell:
1. ACarries the t(9;22) translocation
2. BHas lost one chromosome 9
3. CHas an extra chromosome 22
4. DHas a normal signal pattern
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Question 16 · Hard
A healthy man's karyotype is 45,XY,der(21;21)(q10;q10). For each of his pregnancies that reaches live birth, the chance of Down syndrome is close to:
1. A33%
2. B1%
3. C100%
4. D50%
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Question 17 · Easy
The Philadelphia chromosome comes from a reciprocal translocation between which chromosomes?
1. A8 and 14
2. B15 and 17
3. C9 and 22
4. D11 and 22
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Question 18 · Medium
In interphase FISH, a centromeric (alpha-satellite) probe for chromosome 18 is best used to detect:
1. AA small deletion
2. BA point mutation
3. CTrisomy 18
4. DA balanced translocation
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Question 19 · Easy
Which banding method is used for routine karyotyping in most cytogenetics laboratories?
1. AG-banding
2. BNOR staining
3. CQ-banding
4. DC-banding
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Question 20 · Medium
The dark bands seen after G-banding are generally regions that are:
1. AGC-rich and gene-rich
2. BMade of satellite DNA only
3. CAT-rich and gene-poor
4. DTelomeric repeat sequences
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Question 21 · Medium
An isochromosome, formed when the centromere divides crosswise instead of lengthwise, consists of:
1. AA ring with no free ends
2. BAn arm with an inverted segment
3. CTwo centromeres in one chromosome
4. DTwo copies of the same arm
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Question 22 · Easy
What is a cell with 69 chromosomes, three complete sets, called?
1. ATriploid
2. BTrisomic
3. CTetraploid
4. DMonosomic
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Question 23 · Medium
What does silver (Ag-NOR) staining of metaphase chromosomes show?
1. ACentromeric heterochromatin
2. BActive nucleolar organiser regions
3. CTelomeric repeat sequences
4. DThe inactive X chromosome
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Question 24 · Easy
Which syndrome is usually caused by a structural, not a numerical, chromosome abnormality?
1. APatau syndrome
2. BCri-du-chat syndrome
3. CEdwards syndrome
4. DKlinefelter syndrome
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Question 25 · Medium
In the usual C-banding method, slides are first treated with:
1. ABarium hydroxide
2. BSilver nitrate
3. CHot phosphate buffer
4. DTrypsin
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Cytogenetics: banding, abnormalities and advanced methods

An important advantage of FISH over conventional karyotyping is that FISH:

R-banding produces a pattern that is:

The Philadelphia chromosome is characteristic of which disease?

A baby born to a 41-year-old mother has Down syndrome, with 47 chromosomes in every cell counted. The most likely cause is:

A 2-year-old with Down syndrome has 46 chromosomes, one of them a fused 14;21 chromosome. The parents plan another child. The most useful next test is:

Which microscope is needed to examine Q-banded chromosomes?

A girl's karyotype is 47,XXX. How many Barr bodies are expected in her buccal cells?

All of the following are features of Turner syndrome EXCEPT:

What does C-banding mainly stain?

A tall 22-year-old man has small firm testes, gynaecomastia and azoospermia. His karyotype is most likely:

A 38-year-old woman has WBC 85,000/µL with all stages of granulocytes and many basophils. Her bone marrow culture fails, giving no metaphases. Which test can still detect the Philadelphia translocation?

In G-banding, chromosomes are treated with which enzyme before Giemsa staining?

Edwards syndrome is trisomy of which chromosome?

A 3-year-old boy has mild features of Down syndrome. His karyotype is reported as 47,XY,+21[12]/46,XY[8]. This means:

A dual-colour, dual-fusion BCR::ABL1 FISH probe is used (ABL1 red, BCR green). An interphase cell shows one red, one green and two yellow fusion signals. This cell:

A healthy man's karyotype is 45,XY,der(21;21)(q10;q10). For each of his pregnancies that reaches live birth, the chance of Down syndrome is close to:

The Philadelphia chromosome comes from a reciprocal translocation between which chromosomes?

In interphase FISH, a centromeric (alpha-satellite) probe for chromosome 18 is best used to detect:

Which banding method is used for routine karyotyping in most cytogenetics laboratories?

The dark bands seen after G-banding are generally regions that are:

An isochromosome, formed when the centromere divides crosswise instead of lengthwise, consists of:

What is a cell with 69 chromosomes, three complete sets, called?

What does silver (Ag-NOR) staining of metaphase chromosomes show?

Which syndrome is usually caused by a structural, not a numerical, chromosome abnormality?

In the usual C-banding method, slides are first treated with: