- A Both parental genomes are sometimes thought to be expressed at exactly equal levels throughout fetal development, with little asymmetry present in many documented cases according to conventional understanding
- B Certain genes are epigenetically silenced depending on parental origin; some are expressed only from paternal copy, others only from maternal copy; disruption causes developmental disorders
- C All genes within the fetal genome are sometimes thought to be expressed mainly from the maternal copy, with most paternal copies largely silenced in routine practice overall in most cases
- D Genomic imprinting has sometimes been thought to have little detectable effect on fetal development under most circumstances studied so far under typical conditions according to standard textbooks
Correct answer: B. Certain genes are epigenetically silenced depending on parental origin; some are expressed only from paternal copy, others only from maternal copy; disruption causes developmental disorders
Explanation: Genomic imprinting: epigenetic silencing (via DNA methylation, histone modification) of certain genes based on parental origin. IGF2 (paternal) promotes fetal growth; H19 (maternal) limits growth. Prader-Willi syndrome: loss of paternal 15q11-q13 (including SNRPN); Angelman syndrome: loss of maternal 15q11-q13 (UBE3A). These show that both parental genomes are needed for normal development.
Concept context
Male and female reproductive systems, gametogenesis, fertilization, implantation, pregnancy, and reproductive health.