Quick revision: every question with its correct answer. For the full explanation, open the test and tap View Solution.
2.4 Sex-Chromosome Aneuploidies & Pedigree Analysis — Test 1
Q1. A colour-blind father has a daughter who is also colour blind and has Turner's syndrome (XO). Her condition arose by:✓ Non-disjunction in the mother
Q2. Klinefelter syndrome is identified by the karyotype:✓ 47, XXY
Q3. Absence of one sex chromosome (45, XO) causes:✓ Turner syndrome
Q4. The monosomic XO condition in humans is referred to as:✓ Turner's syndrome
Q5. A euploid female with one X chromosome (Turner syndrome) results from:✓ Monosomy of an allosome
Q6. An aneuploid female with only one X chromosome is characteristic of:✓ Turner syndrome
Q7. A person with Klinefelter's syndrome has the chromosomes:✓ XXY
Q8. If an affected male transmits the trait to all his daughters but to none of his sons, the trait is most likely:✓ X-linked dominant
Q9. In X-linked recessive inheritance, which statement is correct?✓ Daughters of an affected father are carriers
Q10. The allele 'l' in Drosophila is recessive, X-linked and lethal when homozygous or hemizygous. If a female Ll is crossed with a normal (L) male, the ratio of females:males in the progeny is:✓ 2:1
Q11. Loss-of-function mutations in the tra and tra-2 genes of Drosophila cause:✓ Only XX embryos to develop as male
Q12. In sheep, horns are produced by an autosomal allele H⁺ that is dominant in males and recessive in females (a sex-influenced trait). A horned female × hornless male gives an F1 female that is crossed with a hornless male. The proportion of horned progeny is:✓ 50% of the males but none of the females
Q13. Autosomal recessive traits often appear in pedigrees with consanguineous matings because such traits:✓ Appear only when both parents carry the recessive allele
Q14. A trait that often skips a generation, appears about equally in both sexes, and is common in consanguineous pedigrees is most likely:✓ Autosomal recessive
Q15. Double (parallel) lines connecting a couple in a pedigree indicate:✓ Marriage between related individuals (consanguinity)
Q16. Which is NOT an expected feature of autosomal dominant inheritance?✓ The trait often skips generations
Q17. Which individual would NOT necessarily carry the allele responsible for the stated trait?✓ A father of a boy affected with an X-linked recessive trait
Q18. Polydactyly is dominant. Of 42 individuals carrying the allele, only 38 actually show extra digits. This illustrates:✓ Penetrance of about 90%
Q19. The four children of the same parents have blood groups A, B, AB and O. The parental genotypes must be:✓ One heterozygous A (IAi) and the other heterozygous B (IBi)
Q20. Match each karyotype/condition with its description and select the correct option.✓ A-ii, B-i, C-iv, D-iii