Gene Expression & Cell Specialization

My AP Biology Thoughts Unit 6 Gene Expression and Regulation

Welcome to My AP Biology Thoughts podcast, my name is Shriya Karthikvatsan and I am your host for episode #110 called Unit 6: Gene Expression and Regulation. Today we will be discussing the mechanisms used by cells to increase or decrease the production of specific gene types, and how this fits into the overarching unit.

Segment 1: Introduction to Gene Expression and Regulation

• We will begin by going over a few helpful terms and ideas to provide context for the topic of gene expression and regulation which is a pretty broad topic as a whole
• A gene consists of a string of DNA hidden in a cell’s nucleus, and what we will unpack is how it knows when to express itself and cause the production of a string of amino acids called a protein
• The overall process is that a string of DNA is expressed to make RNA
• Then, something called mRNA is translated from nucleic acid coding to protein coding to form a protein
• In terms of regulation, genes can’t control an organism on their own so they must interact with and respond to the organism’s environment
• Some genes are always “on” regardless of environmental conditions, and these genes are among the most important elements of the genome because they control the ability of DNA to replicate, express itself, repair itself, and perform protein synthesis
• Overall, regulated genes are needed occasionally and get turned “on” or “off”
• Regulation differs between prokaryotes and eukaryotes because in prokaryotes, most regulatory proteins are negative and turn genes off
• In eukaryotes, cell-cell differences are determined by expression of different sets of genes
• This means that an undifferentiated fertilized egg looks and acts quite different from a skin cell, a neuron, or a muscle cell because of differences in the genes each cell expresses
• In the next segment we will go into further detail of the specific processes involved in expression and regulation

Segment 2: More About Gene Expression and Regulation

• Gene expression begins with transcription which makes mRNA and the overall process is the same in both prokaryotes and eukaryotes
• Prokaryotes lack a nuclear envelope, and eukaryotes use an extra step called RNA processing where RNA is edited and introns are edited out and exons are spliced together
• It is catalyzed by RNA polymerase which separates DNA strands and links RNA nucleotides at the 3’ end (side notes: prokaryotes have 1 type of polymerase and eukaryotes have 3)
• Transcription is initiated when RNA polymerase binds to a promoter and unwinds the DNA strands
• Initiation site and a small sequence after are recognized by transcription factors which are...