Instead of developing a head and a tail, an abnormal Drosophila embryo develops two tails. This is most likely due to __________.

• A. apoptosis
• B. a mutation in an operon
• C. a failure involving post-transcriptional modification of mRNA
• D. destruction of the RNA polymerase molecules responsible for the transcription of genes that encode head-related proteins
• E. a mutation in a maternal effect gene

Answer: (E)

Verified step by step guidance

1. Understand the role of maternal effect genes: These genes are expressed in the mother and their products are deposited into the egg, influencing early development. Mutations in these genes can lead to developmental abnormalities in the embryo.
2. Consider the developmental process of Drosophila: The formation of the head and tail regions in Drosophila embryos is guided by specific genes, including maternal effect genes. These genes help establish the anterior-posterior axis.
3. Evaluate the options: Apoptosis is a process of programmed cell death, which is unlikely to cause the specific abnormality of two tails. A mutation in an operon typically affects bacterial gene regulation, not Drosophila development. Post-transcriptional modification of mRNA and destruction of RNA polymerase would affect gene expression but are not directly linked to the specific abnormality described.
4. Focus on the mutation in maternal effect genes: A mutation in these genes can disrupt the normal patterning of the embryo, leading to the development of two tails instead of a head and a tail.
5. Conclude that the most likely cause of the abnormality is a mutation in a maternal effect gene, as these genes are crucial for establishing the body plan of the embryo.