Which of the following did not occur during the Cenozoic era?
2 answers:
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Answer:
The P generation has straight wings and curly wings.
The F1 generation has all straight wings.
The F2 generation has straight wings and curly wings.
Explanation:
This question involves a single gene coding for wing shape in fruit flies. The allele for straight wings (S) is dominant over the allele for curly wings (s). This means that allele "S" will mask the phenotypic expression of allele "s" in a heterozygous state.
According to the question, the cross follows all Mendel's method of crossing two true breeding parents with opposite traits. Hence, the parent generation (P generation) will be between a truebreeding straight wings parent (SS) and a truebreeding curly wings parent (ss). (See attached image for full cross).
Since the straight wing allele (S) is dominant, all the F1 offsprings will possess straight wings with the genotype: Ss, which is heterozygous.
If this F1 offsprings are self-crossed i.e. Ss × Ss, four possible offsprings in the phenotypic ratio 3 straight wings : 1 curly wing will be produced in the F2 generation. The offsprings will possess the following genotypes: SS, Ss, Ss, and ss.
Offsprings SS, Ss, and Ss will all be phenotypically straight-winged
Offsprings ss will be phenotypically curly-winged.
In overall, this means that P generation has both straight and curly wings (SS and ss), F1 generation has only straight wings (Ss), F2 generation has both straight and curly wings (SS, Ss and ss).
