What part of DNA directs a cell to make a certain protein

A gene is the part of DNA that produces the certain proteins.

A gene

Explanation: A gene is the part of DNA that encodes information needed to produce a functional biological product or a protein. DNAs are made up of:

1). segments that do not code for any biological functional product or protein. These DNA segments are called introns or intervening sequences.

2). Segments that code for an RNA or a protein. A gene is a segment of a DNA that codes for a protein or an RNA. These segments are called exons.

not necessarily. higher fitness requires the organism to be reproductive successful. for example, an organism at age 10 with 15 offspring is much more fit than an organism at age 15 with only 5 offspring.

which fault and or fold did you find most difficult to diagram