Genes are segments of DNA that contain the code for a specific protein that functions in one or more types of cells in the body. Chromosomes are structures within cells that contain a person's genes. Genes are contained in chromosomes, which are in the cell nucleus. And a trait is a gene-determined characteristic.
Forests may have several tree species but one very important feature of forests is their close canopy of dense trees, often arranged in several strata (or layers).
In eukaryotic cells (ex. plants and animals) the DNA is found in the nucleus of the cell. Structures called ribosomes build proteins (this process is called translation).