In rna the nucleotide is used in place of thymine in dna

In RNA, thymine is replaced with Uracil.

Explanation:

Genetic material (DNA and RNA) is made up of nucleotides. These are Adenine, Thymine, Guanine, Cytosine, and Uracil. Three of them (Adenine, Cytosine, and Guanine) are present in both types of genetic material, i.e. DNA and RNA. However, in DNA Thymine is present whereas in RNA, Uracil replaces Thymine. They are similar in structure except that Thymine has additional methyl group.

the dark variety, as they are not visible on the dark tree barks

explanation:

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.