George beadle and edward tatum used mutant strains of neurospora to formulate the one-gene-one-enzyme hypothesis. researchers later updated this hypothesis to propose that one gene encodes one polypeptide because proteins can have multiple subunits. consider a heterodimeric protein. how many genes are required to form this protein?

(a) two
(b) four
(c) six
(d) three
(e) one

(A) two

Explanation:

A heterodimeric protein consists of two polypeptides (a polypeptide is a  chain of amino acids) that differ in amino acid composition, number or order in the chain sequence. Each polypeptide makes a different subunit of the protein.

One gene encodes one polypeptide, so if the protein has two different polypeptides, two genes are required to form this protein.

answer: ice crystals in air

the water from the water body or another source of water gets evaporated as water vapor as an effect of heat on water. these water vapor rises in the upper layers of the earth atmosphere under high atmospheric pressure. the atmospheric pressure of these water molecules starts to decrease due to the effect of cold air. the invisible water vapor condenses into visible water droplets and ice crystals.these ice crystals and water droplets being less denser than the surrounding air floats on air as clouds.