What kind of letter is used for dominant traits

Upper case letters are used for dominant traits

In biology, a trait or character is a feature of an organism.  A trait refers to any genetically determined characteristic in the body. In technical terms, a genetic trait is amenable to segregation analysis rather than quantitative analysis. Dominant traits are those traits which are expressed even in the presence of one copy of an allele for a particular trait in the gene. For example the letter B is used to represent brown eye color as a dominant allele.

that scientist would be robert hooke

c. heat from the poles back down towards the equator.