Ch. 11 The Control of Gene Expression Flashcards
Gene Expression
When certain regions of the chromosome are transcribed and translated into proteins
- the flow of genetic info from genes to proteins
- to produce proteins when and where needed
- genotype -> phenotype
- regulated by turning on/off transcription
Promoter
Nucleotide sequence at the start of a gene
- start of genes designed to produce certain enzymes
- binding site for active repressor
Operator
The sequence of nucleotides b/w the promotor and gene
- binding site for the active repressor
- shuts transcription down, off switch
Operon
The unit of genetic regulation in prokaryotes
- cluster of genes designed to produce certain enzymes
Repressor
A protein that clocks the transcription of a gene/operon
- proteins that block the transcription of a gene
Regulatory gene
A gene that codes for a protein, such as a repressor, that controls the transcription of another gene or group of genes
- codes for active repressor, located outside the person
Activators
Protein that turns the operon on by binding to the DNA
- switch on gene
Cellular Differentiation
The specialization in the structure and function of cells that occurs during the development of an organism; results from selective activation/deactivation of the cell’s genes
Clone
To produce genetically identical copies of cell, organism, or DNA molecule
Histones
A small basic protein molecule associated w/ DNA and important in DNA packing in the eukaryotic chromosomes
- framework for DNA
- provide structure/organization for DNA strand
Nucleosome
The beadlike unit of DNA packaging in a eukaryotic cell; consists of DNA wound around a protein core made up of 8 histone molecules
What can prevent gene expression?
DNA Packing
X Chromosome Inactivation
Inherited by cell’s descendants
What is the most important stage for regulating gene expression?
Initiation
What differs in eukaryotic genes?
Own promoter and control sequences.
Activator proteins > Repressors
“default state” = “off”
Transcription Factors
In the eukaryotic cell, a protein that functions in initiating or regulating transcription; bind to DNA or to other proteins that bind to DNA
Enhancer
A eukaryotic DNA sequence that helps stimulate the transcription of a gene at some distance from it; functions by means of an activator which binds to it and then to rest of transcription apparatus
- stimulates the transcription of a gene
Silencers
A eukaryotic DNA sequence that functions to inhibit the start of gene transcription; may act analogously to an enhancer by binding a repressor
- inhibits the state of gene transcription
Introns
In eukaryotes, a non expressed (noncoding) portion of a gene; it is excised from the RNA transcript
Exons
In eukaryotes, a coding potion of a gene
RNA splicing
The removal of introns and joining of exons in eukaryotic RNA, forming an mRNA molecule with a continuous coding sequences
- occurs before mRNA leaves nucleus
Alternative splicing
Generating different mRNA from the same RNA transcript
Homeotic gene
A master control gene that determines the identity of a body structure of a developing organism, presumably by controlling the developmental fate of groups of cells
Signal-Transduction Pathway
A series of molecular changes that converts a signal on a target cell’s surface into a specific response inside the cell
What are the steps of Signal-Transduction Pathway?
1) Signaling cell first secrets the signal molecule
2) Signal molecule binds to a specific receptor protein embedded in target cell’s plasma membrane
3) Binding activates the first in a series of relay proteins w/in the target cell
4) Last relay molecule in series activates a transcription factor
5) Factor triggers transcription of specific gene
6) Translation of mRNA produces a protein
Homeoboxes
A 180 nucleotide sequence w/in a homeotic gene encoding the part of the protein that binds to the DNA of the genes regulated by the protein
Why do cells escape from control?
Changes in cell’s gene or how they are expressed
Oncogene
A cancer-causing gene; usually contributes to malignancy by abnormally enhancing the amount/activity of a growth factor made by cell
Proto-oncogene
A normal gene that can be converted to a cancer causing gene
Tumor Suppressor genes
A gene whose product inhibits cell division, thereby preventing uncontrolled cell growth
Carcinogens
A cancer-causing agent, either high energy radiation or a chemical
What is the difference b/w gene expression in prokaryotes and eukaryotes?
Prokaryotes…simple b/c have no cell specialization
Eukaryotes…have different proteins for each cell b/c specialization
What does E. coli do?
Constantly turning genes on/off when the cell is surrounded by sugar or carb or protein etc.
How can the operon be turned on if the repressor is always present?
Lactose binds to the repressor, changing its shape, preventing the repressor from attaching
How does cloning work?
Take an egg cell, expose it to radiation to destroy nucleus
- insert nucleus of a different cell into that cell
- implant into an animal’s womb
What is gene expression based on and what is transcription based on?
Gene expression is based on the regulation of transcription
Transcription is based on the regulation of transcription factors
What is more important for eukaryotes? Activation or repression?
Activation
RNA transcript
The copying of DNA’s code onto mRNA
- result of transcription
What are the 3 modifications added to RNA before leaving nucleus?
1) Capped
- single guanine nucleotide is placed at one end
2) Tailed
- long chain of adenine nucleotides are attached to other end
3) Edited
- Introns are edited out, externs are spliced together
What does capped and tailed modifications do?
Prevents attack from cellular enzymes and identifies mRNA.
What is cancer a disease of?
A disease of gene expression b/w cell escapes control
