MCQ: Genetic Disorders Year 3 End Year

Question 1

Which of the following statements is true?

Accepted Answer

Approximately 5% of individuals under 25 years develop a serious disease with significant genetic component — Roughly 5% of people develop a serious disease with a major genetic component before age 25. Only ~50% (not 100%) of early miscarriages show chromosomal abnormalities; genetic testing/screening is generally neither easy nor cheap. ---

Question 2

The following Mendelian disorders are autosomal dominant except one. Which one?

Accepted Answer

Sickle cell anaemia — Sickle cell anaemia is autosomal recessive. The other four are classic autosomal dominant disorders. ---

Question 3

The following Mendelian disorders are autosomal recessive except one. Which one?

Accepted Answer

Hereditary spherocytosis — Hereditary spherocytosis is autosomal dominant (~75% of cases). The others are autosomal recessive. ---

Question 4

The following Mendelian disorder is an X-linked inheritance disorder

Accepted Answer

Duchenne muscular dystrophy — DMD is X-linked recessive. The rest are autosomal. ---

Question 5

Which of the following statements is false?

Accepted Answer

All sex linked disorders are X-linked recessive disorders — X-linked dominant disorders exist too (e.g., vitamin D–resistant rickets), so not all sex-linked conditions are recessive. ---

Question 6

Which of the following statements is not false?

Accepted Answer

Sickle cell anaemia is an example of a missense mutation — Sickle cell disease results from a missense mutation (Glu→Val at codon 6 of β-globin). The other statements are nonsensical/incorrect. ---

Question 7

Concerning single nucleotide polymorphisms (SNPs) which statement is true?

Accepted Answer

Are almost always biallelic — SNPs are typically biallelic. Millions (not <100) exist; most lie outside coding regions; many are used in disease-risk stratification. ---

Question 8

Concerning copy number variations (CNVs) which statement is false?

Accepted Answer

CNVs do not involve gene coding sequences — CNVs frequently do involve coding sequences/genes, including immune and nervous system gene families. ---

Question 9

Epigenetic changes

Accepted Answer

Are those involving modulation of gene or protein expression in the absence of mutations — Epigenetic changes alter gene expression (methylation, histone modification) without changing the DNA sequence itself. ---

Question 10

True about diseases caused by single gene defects of large effect except one. Which one?

Accepted Answer

Defects of enzyme proteins, receptors and structural proteins all present with similar magnitude of dysfunction — Different classes of protein defects (enzymes vs. receptors vs. structural proteins) produce very different severities of dysfunction — not 'similar magnitude.' ---

Question 11

Which is false?

Accepted Answer

Sickle cell anaemia is a sex-linked autosomal recessive condition — Contradictory/false statement — sickle cell anaemia is autosomal recessive, not sex-linked. ---

Question 12

Which statement concerning Lysosomal Storage Diseases is false?

Accepted Answer

Gaucher disease results from accumulation of mucopolysaccharides in liver/spleen — Gaucher disease is caused by glucocerebrosidase deficiency → glucocerebroside accumulation, not mucopolysaccharides (that's the MPS disorders). ---

Question 13

Which statement regarding complex multigenic disorders is false?

Accepted Answer

Environmental influences hardly modify their phenotypic expression — Gene-environment interaction is a defining hallmark of multigenic disease — environment strongly modifies expression. ---

Question 14

Cytogenetic disorders

Accepted Answer

May result from number or structure alterations, may affect autosomes or sex chromosomes — The comprehensive/correct definition — both numerical and structural, autosomal or sex chromosome. ---

Question 15

True of karyotyping except

Accepted Answer

Useful in identifying point mutations — Karyotyping's resolution (~megabases) is far too low to detect point mutations. ---

Question 16

Which is true?

Accepted Answer

All the above — All definitions/statements are correct. ---

Question 17

In genetic shorthand, 46,XX,t(2;5)(q31;p14) means

Accepted Answer

Reciprocal translocation: long arm of chr 2 (region 3, band 1) and short arm of chr 5 (region 1, band 4) — In ISCN notation, breakpoints are listed in the same order as the chromosomes: chr2 breakpoint = q31 (long arm), chr5 breakpoint = p14 (short arm). ---

Question 18

General features of chromosomal disorders except one. Which one?

Accepted Answer

Chromosomal disorders are usually familial with high sibling recurrence — Most chromosomal disorders arise de novo (sporadic) during gametogenesis, not familial with high recurrence. ---

Question 19

Patau syndrome

Accepted Answer

Involves chromosome 13 — Patau syndrome is trisomy 13. ---

Question 20

Edward syndrome

Accepted Answer

Involves chromosome 18 — Edward syndrome is trisomy 18. ---

Question 21

Down syndrome

Accepted Answer

Involves chromosome 21 — Down syndrome is trisomy 21. ---

Question 22

Cri du chat syndrome

Accepted Answer

Results from partial deletion of the short arm of chromosome 5 — Cri du chat = deletion of the short arm (5p−) of chromosome 5. ---

Question 23

NOT true regarding 22q11.2 deletion syndrome?

Accepted Answer

Confers low risk for psychoses such as schizophrenia and bipolar disorder — 22q11.2 deletion actually confers an INCREASED (not low) risk of psychosis/schizophrenia. ---

Question 24

Skipped generations, male-to-male transmission, equal sex distribution, disease only in homozygotes, carriers are heterozygous — inheritance pattern?

Accepted Answer

Autosomal recessive — Classic autosomal recessive pattern. ---

Question 25

NOT characterized by trinucleotide repeats?

Accepted Answer

Fraccaro syndrome — Fraccaro syndrome (achondrogenesis type 1A) is not a trinucleotide-repeat disorder; the other four are. ---

Question 26

Large everted ears, long face, large mandible, macroorchidism; multiple CGG tandem repeats.

Accepted Answer

Fragile X syndrome — Classic Fragile X syndrome phenotype and FMR1 CGG expansion. ---

Question 27

Familial disorders of structural proteins (vs. enzymes), presenting in adulthood (vs. childhood) — typical inheritance?

Accepted Answer

Autosomal dominant — Structural protein disorders (e.g., collagen defects) with adult onset are classically autosomal dominant. ---

Question 28

Sex-linked recessive inheritance exists in

Accepted Answer

Duchenne muscular dystrophy — DMD is X-linked recessive; the others are autosomal or non-genetic. ---

Question 29

Best estimate of chance of Down syndrome child when the wife carries a 21q21q Robertsonian translocation?

Accepted Answer

15% — With a 21q21q translocation, viable gametes carry either both copies of 21 (→ trisomy 21) or none (→ monosomy 21, non-viable). All surviving pregnancies result in Down syndrome. ---

Question 30

Which statement is not true?

Accepted Answer

Loss of the functional (non-imprinted) allele goes unnoticed since the imprinted gene compensates — This is backwards — losing the one active/functional allele in an imprinted region causes disease precisely because the silenced (imprinted) copy cannot compensate. ---

Question 31

Malformations

Accepted Answer

Occur due to an intrinsically abnormal developmental process — Malformations = primary errors of morphogenesis (intrinsic). C/D actually describe 'deformations,' a different category. ---

Question 32

Disruptions

Accepted Answer

All of the above — All correctly describe disruptions. ---

Question 33

Which is NOT true?

Accepted Answer

Lack of morning sickness is a sign of teratogenesis — Not an established/valid teratogenesis marker as stated — the false option. ---

Question 34

Protective against congenital anomalies?

Accepted Answer

Vaccination against viral agents — Vaccination (e.g., against rubella) prevents virus-induced congenital anomalies. The rest are teratogenic/harmful. ---

Question 35

17-year-old phenotypic female, primary amenorrhea, XY karyotype — diagnosis?

Accepted Answer

Androgen insensitivity syndrome — Classic presentation of complete androgen insensitivity syndrome. ---

Question 36

NOT a karyotype of Klinefelter syndrome?

Accepted Answer

46,XY — 46,XY is a normal male karyotype. ---

Question 37

NOT a clinical manifestation of Klinefelter syndrome?

Accepted Answer

Short stature — Klinefelter patients are classically tall (long limbs), not short — the others are all recognized features. ---

Question 38

NOT a clinical feature of Turner syndrome?

Accepted Answer

Testicular atrophy — Turner syndrome affects females (45,X) — there are no testes. The correct gonadal finding is streak ovaries. ---

Question 39

True of mitochondrial gene mutation diseases except one. Which one?

Accepted Answer

Fathers can only transmit mutations to their daughters — Mitochondrial DNA is strictly maternally inherited — fathers never transmit mtDNA mutations to any offspring. ---

Question 40

Enabled rapid expansion of molecular diagnostics?

Accepted Answer

All of the above — All of the listed advancements have contributed significantly. ---

Question 41

Which statement regarding FISH is false?

Accepted Answer

Is cheap using normal light microscopy in resource-poor settings — FISH requires specialized fluorescence microscopy — it is not a cheap, ordinary-light-microscope technique. ---

Question 42

Utilizations of FISH except one. Which one?

Accepted Answer

Useful in genetic therapy — FISH is diagnostic, not therapeutic — it has no role in 'genetic therapy.' ---

Question 43

True of Array-Based (Comparative) Genomic Hybridization. Which one?

Accepted Answer

Detects chromosomal abnormalities without prior knowledge of the aberration — The defining advantage of array-CGH is genome-wide, unbiased detection without needing to know what abnormality to look for beforehand (unlike targeted FISH probes). Note: c, d, and e are also technically accurate descriptions of the method — b is the key differentiating point being tested. ---

Question 44

NOT true regarding PCR?

Accepted Answer

Requires high resolution microscopy — PCR is a molecular/biochemical technique — it does not involve microscopy at all. ---

Question 45

Indications for postnatal genetic testing include

Accepted Answer

All the above — All are valid indications for genetic testing. ---

Question 46

Similarities between Patau and Down Syndrome except one. Which one?

Accepted Answer

Life expectancy in both ~40 years — Patau/Edwards syndromes have very short life expectancy (usually <1 year); Down syndrome patients often live into their 50s-60s — not comparable. ---

Question 47

NOT true of an adult with karyotype 47,XXY?

Accepted Answer

A 46,XY line in mosaics is usually associated with a MORE severe clinical condition — Actually the opposite — a coexisting normal 46,XY cell line (mosaicism) generally produces a milder phenotype. ---

Question 48

Primary defect (e.g., bilateral renal agenesis) plus its secondary structural change is best termed

Accepted Answer

Sequence — A 'sequence' is a cascade of anomalies triggered by one initiating defect (e.g., Potter sequence from renal agenesis). ---

Question 49

Both parents are CF carriers; 3 children — probability ALL THREE develop cystic fibrosis?

Accepted Answer

1/4 × 1/4 × 1/4 — Each child independently has a 1/4 chance of being affected; probability all three are affected = product of independent probabilities = (1/4)³. ---

Question 50

In tissues affected by the predominant form of Niemann-Pick disease, found at abnormally high levels?

Accepted Answer

Sphingomyelin — Sphingomyelinase deficiency (types A/B) causes accumulation of its substrate, sphingomyelin. ---

MCQ: Genetic Disorders Year 3 End Year

Questions, Answers & Explanations