Dosage compensation in mammals typically involves the random inactivation of one of the two x chromosomes relatively early in development. such x chromosome inactivation often leads to phenotypic mosaicism. assume that black fur in cats is due to the x-linked recessive gene b, whereas its dominant allele b produces yellow fur. a bb heterozygote is a mosaic called "tortoise shell" or "calico." a mating between a black male and a calico female occurred. give the phenotypes of the offspring.

1/4 Xᵇ Xᴮ: calico, female

1/4 Xᵇ Xᵇ : black fur, female

1/4 Xᴮ Y: yellow fur, male

1/4 Xᵇ Y: black fur, male

Explanation:

The fur color in cats is an X-linked trait.

XᴮXᴮ: yellow fur, female

XᴮXᵇ: calico, female

XᵇXᵇ: black fur, female

XᴮY: yellow fur, male

XᵇY: black fur, male

A mating between a black male (XᵇY) and a calico female (XᴮXᵇ) occurred.

The male can produce the gametes Xᵇ and Y. The female produces Xᴮ and Xᵇ gametes.

The following offpsring could be observed from the combination of those gametes:

1/4 Xᵇ Xᴮ: calico, female

1/4 Xᵇ Xᵇ : black fur, female

1/4 Xᴮ Y: yellow fur, male

1/4 Xᵇ Y: black fur, male

correct answer is a. and d.

before, trains worked using the steam engine. thus, it uses heat so it is crucial to apply heat balance. the steam engine absorbs energy during the stage of boiling water. so, this is the endothermic reaction. when the steam is used to work the piston, it has to release this energy through running the train. the excess energy is released as an exhaust to the chimney. this is the exothermic process because it releases energy to the surroundings.