Gene Expression & Regulation Flashcards
Define Epigenetics
The study of heritable phenotype changes that do not involve alterations in the DNA sequence.
Define Operon
A functioning unit of DNA containing a cluster of genes under the control of a single promoter.
An operon consists of a promoter, an operator, and structural genes.
Define Promoter
The site where RNA polymerase attaches, signaling the start of the gene.
Define Operator
The site where a repressor binds, stopping the transcription of that gene.
Define Structural Genes
Genes coding for an enzyme that are transcribed as a unit.
Define Inducible Gene
A gene that needs to be “turned on” or activated in order to be expressed.
Define Repressible Gene
A gene that needs to be “turned off” or deactivated in order to stop being expressed.
Define Enhancer
A DNA sequence that promotes transcription. Each enhancer is made up of short DNA sequences called distal control elements.
Define Single-Nucleotide Polymorphism (SNP)
A DNA sequence variation occurring when a single nucleotide in the genome differs between members of a species or paired chromosomes in an individual.
Define Homeotic Genes (HOX)
Master regulator genes that direct the development of particular body segments or structures.
When HOX are changed by mutations, body plans may undergo drastic changes.
Describe the evolution of gene regulation in prokaryotes
Prokaryotes are single-celled. They evolved to grow and divide rapidly, and must respond quickly to changes in external environment.
Gene regulation:
• turn genes on and off rapidly
• flexibility and reversibility
• adjust levels of enzymes for synthesis and digestion
Describe the evolution of gene regulation in eukaryotes
Eukaryotes are multicellular. They evolved to maintain constant internal conditions while facing changing external conditions, and regulate the body as a whole. They have long term processes for growth and development.
Gene regulation:
• turn on and off a large number of genes
• coordinate the body as a whole rather than serve the needs of individual cells
What are the points of control in gene expression?
The control of gene expression can occur at any step in the pathway from gene to functional protein. • packing/unpacking DNA • transcription • mRNA processing • mRNA transport • translation • protein processing • protein degradation
How does DNA packing regulate gene expression?
DNA packing regulates transcription. If DNA is wrapped tightly around histones, the gene isn’t transcribed.
How do histones contribute to gene regulation?
Histones are eight protein molecules containing positively charged amino acids. These amino acids bind tightly to the negatively charged DNA, regulating transcription.