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

검증된 단계별 안내

Understand the concept of a maternal-effect gene: Maternal-effect genes, like bicoid, are genes whose products (mRNA or proteins) are deposited into the egg by the mother. The phenotype of the offspring is determined by the genotype of the mother, not the offspring's own genotype.

Determine the genotypes of the parents: The female is heterozygous for the bicoid gene (Bicoid+/Bicoid−), and the male is also heterozygous (Bicoid+/Bicoid−).

Predict the offspring genotypes: Perform a Punnett square for the cross Bicoid+/Bicoid− × Bicoid+/Bicoid−. The possible offspring genotypes are Bicoid+/Bicoid+, Bicoid+/Bicoid−, and Bicoid−/Bicoid− in a 1:2:1 ratio.

Determine the phenotypes based on the maternal genotype: Since bicoid is a maternal-effect gene, the phenotype of the offspring depends on the mother's genotype. A heterozygous mother (Bicoid+/Bicoid−) will produce functional bicoid mRNA, so all her offspring will develop normally, regardless of their own genotype.

Conclude the phenotypes: The progeny of this cross will all have normal phenotypes because the mother is heterozygous and can provide sufficient bicoid gene product for proper development.

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주요 개념

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Bicoid Gene Function

The bicoid gene is crucial for early embryonic development in Drosophila, acting as a maternal-effect gene that establishes the anterior-posterior axis. It encodes a transcription factor that regulates the expression of other genes necessary for proper head and thorax formation. Mutations in this gene can lead to severe developmental defects, particularly affecting the anterior structures of the embryo.

Maternal Effect Genes

Maternal effect genes are genes expressed in the mother that produce products (like mRNA or proteins) which are deposited into the egg. These products influence the development of the embryo before the zygotic genome is activated. In the case of bicoid, the maternal contribution is essential for the initial stages of development, meaning that the phenotype of the offspring can be affected by the mother's genotype.

Genotype and Phenotype Relationship

The genotype refers to the genetic constitution of an organism, while the phenotype is the observable physical or biochemical characteristics. In this scenario, the progeny of a cross between two heterozygous bicoid parents will exhibit a range of phenotypes based on the combination of alleles inherited. Understanding this relationship is key to predicting the phenotypic outcomes in the offspring, especially in the context of loss-of-function alleles.

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