Ch.11 How Genes Are Controlled Flashcards
Proteins interact with DNA and turn prokaryotic genes on or off in response to ______ ____.
Environmental changes
The turning on and off of genes is called? It helps organisms respond to environmental changes.
Gene regulation
In gene regulation the genes determine the sequence of what?
The nucleotide sequence of specific messenger RNA molecules
In gene regulation mRNA determines the sequence of what?
Determine the sequence of amino acids in protein molecules
What does a gene that is turned on do?
It is being transcribed into mRNA with the message being transcribed into specific proteins molecules.
This is the overall process by which genetic information flows from genes to proteins-genotype to phenotype. It makes it possible for cells to provide specific kinds of proteins when and where they are needed.
Gene expression
Most enzymes are proteins and their production is an outcome of ____ _____.
Gene expression
These are short sections of DNA that help control the expression of these genes.
Control sequences
These are the site on a control sequence where the transcription enzyme, RNA polymerase, attaches and initiates transcription.
Promoter
This is a switch between the promotor and the enzyme genes. It determines whether RNA polymerase can attach to the promoter and start transcribing the genes
Operator
This is a cluster of genes with related functions along with the control sequence.
Operon
Operons only exist in _____.
Prokaryotes
A single on/off switch can control what?
The whole gene cluster of an operon.
When an operon is turned off what happens to transcription?
Transcription is turned off because of the repressor.
What is a repressor and what does it bind to?
The repressor physically blocks the attachment of RNA polymerase to the promotor. It binds to the operator.
This codes for the repressor and is where the repressor comes from. It is located outside the operon.
Regulatory gene
What happens when the operon is turned on?
- Lactose interferes with the attachment of the repressor by binding to it and changing its shape.
- The switch remains open because the repressor cannot bind to the operator.
- RNA polymerase is then able to bind to the promotor and transcribe the genes of the operon.
mRNA has multiple codons signaling the ____ and ____ of translation.
Start and stop
This is an operon that is usually turned off but can be stimulated by a molecule
Inducible operon
This type of operon is normally turned on but can be inhibited when a specific molecule is present in abundance.
Repressor operon
These are proteins that turn on operons by binding to DNA and stimulating gene transcription.
Activators
______ act by making it easier for RNA polymerase to bind to the promotor rather than blocking.
Activators
Chromosome structure and chemical modifications can affect _____ ______.
Gene expression
All organisms must be able to turn off and on ___ in response to signals from their internal and external environments
Genes
This is the specialization in the structure and function of cells that occurs during development of an organism.
Differentiation
Differentiation results from what?
Results from the selective activation and deactivation of the cells genes.
Differences between cells is due to ____.
Selective gene expression
These are small proteins in DNA. They are important in DNA packing in the eukaryotic cell and account for 1/2 the mass of the chromosome.
Histones
This is a “bead” DNA wound around a protein core of 8 histone molecules
Nucleosome
These are short stretches of DNA that join consecutive “beads” of nucleosomes.
Linkers.
This tends to block gene expression by preventing RNA polymerase and other transcription proteins from contacting the DNA.
DNA packing.
Eukaryotic chromosomes can be chemically modified in ways that help regulate _____ ______.
Gene expression
Inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence.
Epigenetic inheritance
In females one X chromosome in each somatic cell is chemically modified and highly compacted rendering it almost entirely inactive.
X inactivation
X inactivation requires the modification of ____ and ____ proteins that help compact it.
DNA and histone
When is X chromosome inactivation initiated?
Early in embryonic development.
This is the inactive x in each cell of a female. It is condensed into a compact object.
Barr body
In your body a nerve cell has a very different structure and performs very different functions than a skin cell. Because the two cell types have the same genes how can the cells be so different?
Each cell type must be expressing certain genes hat are present in but not expresses in the other cell type.
Complex assemblies of proteins control _____ ____.
Eukaryotic transcription
What is the most important stage for regulating gene expression?
The initiation of transcription.
_______ proteins are more important than repressors in eukaryotic cells.
Activators
What is the default state for most genes?
“Off”
What is the exception to the default state of “off” for most genes?
Housekeeping genes that are continually active in all cells for routine activities.
A protein in the eukaryotic cell that functions in initiating or regulating transcription are called?
Transcription factors
What do transcription factors bind to?
DNA or other proteins that bind to DNA.
These are DNA control sequences located far away on the chromosome to help regulate.
Enhancers
RNA processing includes what?
- Addition of a cap and tail
- Removal of introns
- Splicing together of the remaining exons.
Splicing process may help control the flow of ______ from nucleus to cytoplasm.
mRNA
What happens once splicing is complete?
The RNA is attached to the molecules of the splicing machinery and passes through a nuclear pore.
A cell can carry out splicing in more than one way generating different mRNA molecules from the same RNA transcript.
Alternative RNA splicing.
Each kind of polypeptide is encoded by an mRNA molecule containing a different combination of exons through what process?
Alternative splicing.
