AP BIOLOGY

Detailed explanation-1: -Gene expression is largely regulated at the transcription initiation site in prokaryotes. Regulatory proteins control the activity of RNA polymerase in recognizing the promoter region. Positive regulation is controlled by activators, while negative regulation is controlled by repressors.

Detailed explanation-2: -Positive experiences, such as exposure to rich learning opportunities, and negative influences, such as malnutrition or environmental toxins, can change the chemistry that encodes genes in brain cells-a change that can be temporary or permanent. This process is called epigenetic modification.

Detailed explanation-3: -In bacteria, genes are available for expression by default, but they are actively switched off by repressor proteins. Repressor proteins regulate expression by binding to a DNA sequence, called the operator, which is near the promoter of an operon, or a cluster of co-regulated genes.

Detailed explanation-4: -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.”