AP BIOLOGY

Detailed explanation-1: -Each cell expresses, or turns on, only a fraction of its genes at any given time. The rest of the genes are repressed, or turned off. The process of turning genes on and off is known as gene regulation. Gene regulation is an important part of normal development.

Detailed explanation-2: -DNA Methylation Typically, this group is added to specific places on the DNA, where it blocks the proteins that attach to DNA to “read” the gene. This chemical group can be removed through a process called demethylation. Typically, methylation turns genes “off” and demethylation turns genes “on.”

Detailed explanation-3: -That is how gene regulation works during transcription. A protein, called the transcription factor, can either cover up the gene directions or reveal them, thus determining whether the gene is on or off.

Detailed explanation-4: -As researchers untangled the genetic code and the structure of genes in the 1950s and 60s, they began to see genes as a collection of plans, one plan for each protein. But genes do not produce their proteins all the time, suggesting that organisms can regulate gene expression.

Detailed explanation-5: -Similarly, drugs, chemicals, temperature, and light are among the external environmental factors that can determine which genes are turned on and off, thereby influencing the way an organism develops and functions.