Just like chromosome, HTML consist of codes (DNA) that help structure the "body" of the web page

Just like genotype, CSS consist of codes that help give appearances to the web page

JavaScript uses scripts to help branch the Front-end and Back-end to a Database (Brain) to make the web page become functionable (Sensory) and interactive (Motor) for the users

With the help of HTML, CSS, and JavaScript, they create the visual look for the web page. This refers to as Front-end. HTML and CSS give the appearance while JavaScript is the nerves. If a person's nerves have any problem and become paralyzed. Their look will become awkward and you need a Front-end developer to help fix it. For more details on looking under Job Field

Back-end send and retrieve information from the Database (Brain) like the Spinal Cord. With the help of JavaScript (Nerves), it help make the web page become functionable (sensory) and be interactive (motor).

Just lIke the brain, the Database storage information that the web page need.