The bicoid gene is a coordinate maternal–effect gene. A female that is homozygous for a loss-of-function bicoid allele is mated to a wild-type male. What are the phenotypes of their progeny?

Key Concepts

Maternal Effect Genes

Maternal effect genes are genes expressed in the mother that influence the phenotype of the offspring, regardless of the offspring's own genotype. These genes produce products, such as proteins or RNAs, that are deposited in the egg during oogenesis. In the case of the bicoid gene, it plays a crucial role in establishing the anterior-posterior axis in the developing embryo.

Bicoid Gene Function

The bicoid gene is essential for proper embryonic development in Drosophila, as it encodes a transcription factor that regulates the expression of other genes necessary for head and thorax formation. A loss-of-function mutation in the bicoid gene results in embryos lacking anterior structures, leading to severe developmental defects. Understanding its role helps predict the phenotypic outcomes in progeny when the gene is mutated.

Homozygous vs. Wild-Type

In genetics, homozygous refers to having two identical alleles for a particular gene, while wild-type refers to the typical form of a gene found in nature, often associated with normal function. In this scenario, the female is homozygous for a loss-of-function bicoid allele, meaning she cannot produce functional bicoid protein, while the male is wild-type. This genetic combination will determine the phenotypes of their progeny, which will likely exhibit defects due to the absence of bicoid function.