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5.8 Aneuploidy & Nondisjunction — Test 3
Q1. During meiosis, if one chromosome lacks a homologous partner while all others are paired, the aberration is termed:✓ Monosomy
Q2. Autosomal and sex-chromosome trisomies in humans arise mainly due to:✓ Nondisjunction of chromosomes during meiosis
Q3. If nondisjunction occurs in meiosis I, the four resulting gametes are expected to be:✓ Two n+1 and two n-1
Q4. If nondisjunction occurs in meiosis II (in one secondary cell), the four gametes are expected to be:✓ One n+1, one n-1, and two normal (n)
Q5. A meiosis (in a cell) produces four products: two aneuploid and two normal haploid. This indicates nondisjunction occurred during:✓ Meiosis II only
Q6. If a gamete produced by a meiosis-II nondisjunction is fertilised by a normal gamete, the expected frequency of a trisomic zygote among the products of that meiosis is:✓ 1/4
Q7. Turner syndrome results from:✓ Monosomy of a sex chromosome (45,X)
Q8. A phenotypically normal female has 47 chromosomes. Her most likely chromosome complement is:✓ 44 + XXX
Q9. Klinefelter syndrome corresponds to the chromosome complement:✓ 44 + XXY
Q10. A zygote forms from a normal gamete and a gamete lacking one chromosome (due to a meiosis-II segregation failure). The result is:✓ Aneuploidy (monosomy)
Q11. The condition 2n − 2 (loss of both homologues of one pair) is called:✓ Nullisomy
Q12. A colour-blind father has a daughter who is also colour blind AND has Turner syndrome (45,X). The single X she carries came from her father, so the nondisjunction occurred in the:✓ Mother
Q13. An autotetraploid (4n) arises by doubling a diploid. At meiosis, pairing as two bivalents or as one quadrivalent can both yield:✓ Balanced diploid (2n) gametes
Q14. Two inbred parental lines are crossed so that the endosperm of the F1 seed is 6n. If plants from these F1 seeds are backcrossed to a parent, the ploidy of the somatic cells of the next generation is:✓ 4n
Q15. Species 1 is diploid with 2n = 6 (AABBCC). A double trisomic of species 1 would have how many chromosomes?✓ 8
Q16. An aneuploid female with only one X chromosome (45,X) characteristically has:✓ Turner syndrome
Q17. A cell that produces gametes of types n, n+1 and n-1 has most likely undergone:✓ Nondisjunction
Q18. Down syndrome most commonly results from:✓ Nondisjunction giving trisomy 21
Q19. Species 2 is diploid with 2n = 4 (PPQQ). Nullisomy in species 2 would generate how many chromosomes?✓ 2
Q20. Match each chromosomal condition with its description and select the correct option.✓ A-iii, B-i, C-ii, D-iv