You are studying two traits in fruit flies: Eye color where there are two colors, brown and red, and wing shape where there are
straight and curled phenotypes. You mate two flies that are heterozygous for the genes that control both of these traits and get the following phenotypes in the following ratio: 9 red and straight; 3 red and curled; 3 brown and straight; 1 brown and curled. Considering these traits, which alleles separated at which stages of meiosis? Select one:a. Red segregated from brown in meiosis II, and straight segregated from curled in meiosis II.b. Red segregated from brown in meiosis I, and straight segregated from curled in meiosis II.c. Red segregated from brown in meiosis II, and straight segregated from curled in meiosis I.d. Red segregated from straight in meiosis I, and brown segregated from curled in meiosis II.e. Red segregated from brown in meiosis I, and straight segregated from curled in meiosis I.
Red segregated from brown in meiosis I, and straight segregated from curled in meiosis I.
Explanation:
According to independent assortment genes for different traits separate independent of each other. Hence in a dihybrid cross the progeny comes out in 9 : 3 : 3 : 1 ratio. Here the same ratio is observed in a dihybrid cross hence the two genes assort independently.
According to law of segregation, alleles of a gene separate from each other during gamete formation. It can be observed during meiosis I. Homologous chromosomes line up in random orientations in middle of the cells. The chromosomes cross over and then separate. Hence, here the red trait segregated from brown and straight segregated from curled in Meiosis I. It is called as reductional division as after it chromosome number reduces from diploid to haploid.
Having an extra finger, also known as polydactyly, is relatively rare, and people with polydactyly are unlikely to have children with the trait unless both the mother and father <u><em>both</em></u> have it, making it a recessive trait.
As the diaphragm relaxes, the pleural cavity contracts, which exerts pressure on the lungs. As a consequence, the volume of the lungs reduces and the air is passively pushed out of the lungs. Exhalation is passive, thanks to the elastic properties of the lungs.
There are an estimated 200 million microvilli per square millimeter of small intestine, greatly expanding the surface area of the plasma membrane and thus greatly enhancing absorption.
