Which one of the following combinations is correctly matched?
(1) A – ii, B – i, C – iii, D – iv,
(2) A – i, B – iii, C – iv, D – ii,
(3) A – iv, B – ii, C – i, D – iii,
(4) A – iii, B – iv, C – ii, D – i

Maternal effect genes encode messenger RNAs localized in specific regions of the Drosophila egg, crucial for establishing the anterior-posterior axis during embryogenesis. Mutations in these genes disrupt normal development, resulting in characteristic phenotypes.

The primary maternal effect genes and their associated mutant phenotypes are:

• Bicoid (A): Mutation results in loss of anterior structures such as head and thorax.

• Nanos (B): Mutation leads to loss of posterior abdominal segments.

• Hunchback (C): Mutation results in loss or alteration of anterior segments.

• Caudal (D): Mutation affects development of posterior segments and abdominal patterning.

Among the options provided for correct gene-phenotype matches, option (1) aligns with the known functional roles:

• A – ii (Bicoid: loss of head and thoracic structures)

• B – i (Nanos: loss of posterior structures)

• C – iii (Hunchback: anterior segment defects)

• D – iv (Caudal: posterior segment defects)

This correct pairing reflects the foundational understanding of maternal gene function in early Drosophila development and patterning.

Answer: (1) A – ii, B – i, C – iii, D – iv