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positive gene regulation
activator protein binds to operator for expression to occur
negative gene regulation
repressor protein that is normally bound to the operator of DNA must be removed in order for expression to occur
constitutive regulation
genes that are always on and involved in metabolic processes without any regulation mechanism
"housekeeper genes"
inducible regulation
mechanism that actively turns genes on
repressible regulation
mechanism that actively turns genes off
promoter
nucleotide sequence to which RNA pol binds to and initiates transciption
operon
a group of genes that make up a regulatory or control unit.

consists of the operator, promoter, and various structural genes.
activator
product of a regulator gene that turns or, or activates, the expression of other genes
repressor gene
a gene that encodes a repressor protein that turns off gene expression
structural genes
genes that specify for the synthesis of polypeptides
Regions of lac operon
PI-I-|P-O-LACZ-LACY-LACA|
PI- I gene promoter. Promoter for regulatory gene.
I- I gene repressor. Regulatory gene that codes for repressor protein.
P- Promoter for structural genes
O-Operator- segments of DNA that repressor/activator bind to
LacZ- b-galactosidase, cleaves lactose
LacZ- b gal permease, membrane bound prot pumps lactose into cell
LacA- b gal transacetylase. transfers acetyl group
inducible operons- genes that are actively turned on

lac operon uses a negatively controlled inducible operon
-lactose present-
binds to the repressor and causes it to release from the operator, causing the expression of structural genes

-glucose present-
repressor bound to gene that codes for b-gal structural genes
repressible operons- genes that are actively turned off

tryp operon is a negative repressible operon
-tryp absent-
genes are turned on to synthesize trp

-tryp present-
co-repressor/repressor binds to the operator region and prevents RNA pol from transcribing
graphs of induction and repression

minutes vs activity of enzymes involved in lactose utilization
induction-
when lactose is added, enzymes required for the catabolic pathway of lactose are created and used

repression-
of enzyme synthesis. turns off synthesis of tryp when there are high levels present. low levels of enzyme syn always occur wether meabolites are present or absent
Jacob and Monod 1961
Developed the operon model (negative control mechanism) to explain the regulation of genes requried for lactose utilization in e coli.

proposed that transctip of a set of contiguous structural genes is regulated by 2 controlling elements, the repressor and operator.
Lac Operon- glucose absent
-set of genes required to break down lactose in prokaryotes when glucose is absent.

-consists of promoter, operator, and structural genes ZYA

-gene promotoer and repressor are upstream from operon

-when Lac+ Glu-, regulator gene (I) is expressed.

-Lactose (the inducer) binds to the I protein repressor and prevents it from binding to the operato.
Lac Operon- glucose present
-lac operon is downregulated and uses catabolite repression

-cAMP and CAP required to bind to lac op promoter

-glucose prevents ATP from becoming CAMP. since both cAMP and CAP are required, when there are low concentrations of cAMP, RNA pol cannot sucessfully bind to the promoter without the said complex.
transciption factors
a protein that regulates the transcription of genes
alternate splicing
a single gene can code for many polypeptides

exons of RNA are reconnected in multiples ways during RNA splicing resulting in different RNAs.

proteins that are related. Isoforms
heat shock proteins
proteins activated by heat.
maintain cellular environment
expression increased when cells are exposed to elevated temperatures
act as molecular chaperones to prevent denaturation
peptide hormones
linear chains of amino acid that are too large to traverse cell membrane.
transmits signals to interior of cell by membrane bound receptor in a process known as signal transduction.
steroid hormones
small, lipid based molecules that enter a cell and bind to receptors in the cell.
hormone response elements
-sequences that mediate hormone induced gene expression.
-DNA binding sites for transciption factors
basal transcription factors
bind to specific sequences within the promoter to facilitate RNA polymerase binding.
In translational regulation, what factors influence RNA stability and longetivity?
Poly adenylation.
-poly A tail on the 3' end of processed RNA
-longer tail=longer life in cell
Environmental and biological factors affecting transciption?
heat & light
heat
-use heatshock proteins. Turn on at high temps. Prevents other proteins from changing shape and helps to stabilize the cellular environment working as molecular chaperones.
light- RBC in plants, a photosynthetic enzyme that is light induced. changes shape in light.

Biological hormones
steroid
- hormones taht are small and lipid based molecules. go into cell and bind to hormone receptors.
peptide- large amino acid linear molecules. bind to receptors out of cell.
Explain how heat can regulate protein expression?
Heat shock protein transcription factors are activated by heat.

-code for heat shock proteins.
-serve as molecular chaperones in cell.
-prevent other proteins from changing shape.
-help to stabilize cellular environment during heat stress.
How do peptide hormones control gene expression?
1) hormone binds to membrane receptor
2) hormone/receptor activates cytoplasmic protein
3) cytoplasmic protein transduces signal to nucleus
4) signal induced transcription factos bind to DNA hormone response element
5) bound transcription factos stimulate transctiption

-active conformational change in signal molecule
-secondary molecule
How do steroid hormones control gene expression?
1) steroid hormone enters target cell and binds with hormone receptor.
2)hormone/receptor complex binds to hormone response element in DNA
3) complex stimulates transcription
What is meant by the statement "molecular control of transcription"?
The transcription of eukaryotic proteins and DNA sequences within or near the genes.

Basal- transcripton factos that bind to specific sequences within the promoter to faciliates RNA pol binding

special- transcription factors bind to response elements. enhances sequences that are located near a gene that may interact with basal and RNA pol.
cell differentiation
the process in which unspecialized cells develop charateristic structures and functions
cell determination
the process in which undifferentiated cells in an embryo become committed to develop into a specific cell type
cell specialization
the act of specialization of a cell to perform a specific function
morphogenesis
the development of form.

cell in specific locations become spatially organized into recognizable structures
imaginal discs
the mass of cells in the larvae of drosophils that give rise to particular adult organisms such as antenna, eyes, and wings
gap genes
-define segmental regions on embryo
-act on small group of body segments
-1st set of segmentation genes to be expressed.
-regulate the pair rule genes-
pair-rule genes
-affect patterns of segements in embryo
-divide embryo into 14 parasegments
-regulate the segment-polarity genes
segement polarity genes
-define the anterior and posterior compartments of individual segments along the anterior-posterior axis.
homeobox genes
-dna sequence that are involved in the specification of organs in different body parts in animals
-characteristics of genes that influence segmentation
morphogens
-a substance that stimulates the development of form or structure in an organism.
What is morphogenesis?
Morphogenesis is the development of form in an organism. Differential gene expression.

Cells in specific locations become spatially organized to form recognizable structures.
What does morphogenesis require?
Requires:
-signaling between cells
-cell migration
-ability for cells to change shape
Why is drosophila a good model organism for development?
-small chromosome # 2N=4
-many mutants are readily available
-developmental mutations have been identified
-genome sequenced
-many known mutants
-genes that determine form
-developmental homologs between fly and other organisms
-common set of developmental genes shared with other organisms.
Overview of drosophila life cycle
  1. egg fertilized and oviposited in rotting fruits
  2. egg surrounded by hard chorion with filaments for O2
  3. very rapid cell division to create a synctium, cell with multiple identical nuclei
  4. nuclei migrate to membrane on periphery of embryo and develop their own membranes
  5. embryo develops into larva after 1 day
  6. chews its way through egg shell and obtains nutrients from fruit.
  7. molts several times
  8. hardens to form pupae. larva tissue destroyed and imaginal discs take form
  9. completes with mature form
What are maternal effect genes?
Where do they come from?
What is their main function?
-a gene from the maternal genome whose products are required for early embryonic developments, such as the establishmetn of overall polarity of the embryo
-a gene whose produces acts in teh offspring of the female who carries the gene
-phenotype not seen in mother
Gap gene and mutation
-define segmental regions in embryo
-act on small group of body segments
-first set of segmentation genes to be expressed

mutation
-causes absense in one or more body segments in an embryo
Pair-rule gene and mutation
-affect pattern of segments in embryo
-divide embryo into 14 parasegments

mutation
-1/2 as many parasegments (every other missing)
-fushi tarazu and even skipped
Segment polarity gene and mutation
define anterior and posterior compartments in individual segments alond the anterior-posterior axis

mutation
-cause part of each segments to be replaced by a mirror image copy of an adjoining 1/2 segment.
What are hox gene clusters?
-one of a group of genes within a shared nucleotide segment that are involved in the formation of bodily segmentation durying embryonic development.
Why is differential expression of hox genes important?
-differentiation is the final step in cell determination
-cell becomes irreversibly committed.
-causes differences among cell types
-hox genes of all animals exist in clusters and correspond to the order of body regions as they develop
-can specify the identity of each segment as it acts later in development.
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