Final answer:
Genes are the functional units of chromosomes and contain instructions for making proteins, affecting various traits in an organism. Hundreds or thousands of genes can be found on a single chromosome, collectively influencing the organism's development and function.
Step-by-step explanation:
Chromosomes are coiled structures made of DNA and proteins, specifically histones, which are responsible for packaging and organizing the DNA in the cell nucleus. The DNA that makes up these chromosomes is encoded with genetic instructions, which are organized into functional units referred to as genes. These genes contain the instructions necessary for making proteins, which are crucial for the development and functioning of an organism. Most genes are in charge of the instructions for a single protein, but since there can be hundreds or even thousands of genes on a single chromosome, the potential for encoding various proteins is significant. Each gene can influence one or more visible characteristics, known as traits, such as eye color or hair color, which result from the combined effects of genetic makeup and environmental factors.
For example, a particular gene might be responsible for determining hair color, with different alleles of that gene resulting in blonde, brunette, or red hair. During cell division, it is essential that the DNA remains intact, so the chromatin condenses into chromosomes, efficient structures for safely transporting genetic material to new 'daughter cells.' The study of the complete set of genetic material within an organism is referred to as genomics, and within the realm of eukaryotic organisms, such as humans, this involves careful organization of chromosomes within the nucleus.