No, a cat cannot get pregnant by a dog. This is because cats and dogs are different species, which means that they have different numbers of chromosomes and genetic makeup. As a result, they cannot interbreed and produce offspring.
Cats have 38 chromosomes, while dogs have 78 chromosomes. Chromosomes are bundles of genetic material that contain the DNA of an organism. When two organisms mate, their chromosomes combine to form a new set of chromosomes in their offspring. However, because cats and dogs have different numbers of chromosomes, their genetic material cannot combine in this way.
Even if cats and dogs could mate, there would still be other biological barriers to producing offspring. For example, their reproductive systems are not compatible. Cats and dogs have different reproductive organs and mating behaviors, which means that they would not be able to successfully mate in the first place.
In addition, even if a cat and a dog were able to mate and produce offspring, the offspring would likely be sterile. This means that they would not be able to produce their own offspring because their reproductive systems would not work properly. Sterility is a common result of interbreeding between different species because their genetic material is not fully compatible.
There are some cases where different species can interbreed and produce offspring, but these cases are rare and usually involve closely related species. For example, horses and donkeys can mate to produce mules, which are a hybrid offspring. However, mules are usually sterile and cannot produce their own offspring. Similarly, ligers (a cross between a lion and a tiger) and zonkeys (a cross between a zebra and a donkey) are also hybrid offspring, but they are also sterile.
In conclusion, cats and dogs cannot interbreed and produce offspring because they are different species with different numbers of chromosomes and genetic makeup. Even if they could mate, their reproductive systems are not compatible, and any offspring they produced would likely be sterile. Therefore, it is impossible for a cat to get pregnant by a dog.