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9.3 Dosage Compensation & Genomic Imprinting โ Test 2
Q1. In mammals, dosage compensation equalises X-linked gene expression between the sexes by:โ Inactivating one X chromosome in each female cell
Q2. The molecular modification most associated with maintaining X-chromosome inactivation is:โ DNA methylation
Q3. Dosage compensation in Drosophila is achieved by:โ Hyperactivating the single X in males
Q4. Dosage compensation (as an equalising mechanism for X-linked genes) is found in:โ Insects and mammals
Q5. The pattern of genomic imprinting is maintained across cell generations by:โ DNA methylation
Q6. A gene that is expressed when inherited from the father but silent when inherited from the mother is an example of:โ Genomic imprinting
Q7. A mouse with two normal Igf2 alleles is normal; with two mutant alleles it is dwarf. The size of a heterozygote depends on which parent contributed the wild-type allele. This is:โ Genomic imprinting
Q8. An important property of epigenetic changes (such as methylation marks) is that they:โ Can be inherited from a cell to its daughter cells
Q9. A mouse gene A is needed for normal growth. The cross Aแตแตหก A (mutant from father) ร AA gives all-normal offspring, but the cross Aแตแตหก A (mutant from mother) ร AA gives 50% small offspring. This is explained by:โ Maternal imprinting (the maternal allele is silenced)
Q10. Which statement about DNA methylation is FALSE?โ Methylation typically occurs at the 5th carbon of cytosine, forming 5-methylcytosine
Q11. The number of Barr bodies in a cell is related to the number of X chromosomes as:โ Number of X chromosomes minus one
Q12. X-inactivation is initiated by a non-coding RNA called:โ XIST
Q13. Prader-Willi and Angelman syndromes, which involve the same chromosomal region (15q11-q13) but different parental origins, are classic examples of:โ Genomic imprinting
Q14. During mammalian gametogenesis, genomic methylation (imprinting) marks are:โ Erased and then reset according to the sex of the individual
Q15. Maintenance DNA methyltransferase (Dnmt1) preferentially acts on:โ Hemimethylated CpG sites after replication
Q16. The inactive X chromosome in a female somatic cell is an example of:โ Facultative heterochromatin
Q17. In C. elegans, dosage compensation in XX hermaphrodites is achieved by:โ Halving transcription from both X chromosomes
Q18. Random X-inactivation makes female mammals:โ Functional mosaics for X-linked genes
Q19. Imprinted genes are notable because, unlike most genes, they are:โ Expressed from only one parental allele
Q20. Match each phenomenon with its mechanism and select the correct option.โ A-ii, B-iii, C-i, D-iv