In cats, the Manx (M) allele causes a short or absent tail, while a recessive allele (m) confers a normal, long tail. Cats of genotype MM are never born alive, as the M allele is fatal before birth when homozygous, because the spinal cord never develops. If 2 Manx cats mate, what proportion of living offspring will have long tails?

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.

for example, no new evidence will demonstrate that the earth does not orbit around the sun (heliocentric theory), or that living things are not made of cells (cell theory), that matter is not composed of atoms, or that the surface of the earth is not divided into solid plates that have moved over geological timescales .