Lecture 13
what does the fluorescent cDNA represent
all of the genes being actively transcribed in the cell
what does the operator do in lac operon
all the enzymes needed to metabolize lactose are made at once
cloning example in agriculture
farm animals with specific sets of desirable traits might be cloned to produce identical herds
how can a cell acquire an oncogene
from a virus or from the mutation of one of its own proto-oncogenes
if the animal cloned is a mammal
further development requires implanting the early embryo into the uterus of a surrogate mother. the resulting animal will be a clone of the donor
"housekeeping" genes
genes that are turned on in multicellular eukaryotes because of the routine activities such as the digestion of glucose
cloning example in research
genetically identical animals can provide perfect "control animals" for experiements
adult stem cells from donor bone marrow
have been used as a source of immune system cells in patients whose own immune systems have been destroyed by disease or cancer treatments
cell signaling
in a multicellular organism, the regulation process can cross cell boundaries, allowing information to be communicated between and among cells
example of protein activation
insulin is synthesized as one long inactive polypeptide that must be chopped into pieces before it becomes activex
transcriptional regulation
involved many proteins (called transcription factors) acting in concert to bind to DNA sequences called enhancers to the promoter
nuclear transplantation
involves replacing the nucleus of an egg cell or a zygote with a nucleus removed from an adult body cell
what happens with the collection of mRNA
is mixed with reverse transcriptase
what does the binding of the signal molecule activate
it activates a signal transduction pathway consisting of a series of relay proteins within the target cell. each relay molecule activates the next
what can RNA polymerase now do
it is no longer blocked so it can bind to the promoter and transcribe the genes for the lactose enzymes into mRNA
what process is animal cloning acheived through
nuclear transplantation
bacterial operons
operons that control amino acid synthesis cause bacteria to stop making these molecules when they are in the environment, saving materials and energy for the cells
activators
proteins that turn genes ON by binding to DNA
reproductive cloning
results in birth of a new animal
genes coding for related enzymes
share specific kind of enhancer, allowing the genes to be activated at the same time
enhancer
short region of DNA that can be found by TF proteins to increase the likelihood that transcription of a particular gene will occur
what does excessive exposure to UV radiation cause
skin cancer, and more deadly skin cancer melanoma
microRNAs
small single-stranded RNA molecules
what does the last relay molecule do
activates a transcription factor that triggers the transcription of a specific gene
cause of the polyp in colon cancer
the inactivation of the tumor-suppressor gene causes growth of the polyp
RNA interference
the injection of small RNA molecules into a cell to turn off specific genes
how the repressor's shape is changed in lactose operon
the lactose interferes with the attachment of the lac repressor to the operator by binding to the repressor
signal molecule
the molecule binds to a specific receptor protein embedded in the target cell's plasma membrane
gene expression
the overall process by which genetic information flows from genes to proteins
why would cells use DNA packing
for the long-term inactivation of genes
human cloning
the cloning of mammals has heightened speculation that humans are cloned
what percentage of colorectal cancers involve inherited mutations
15%
how many mutations does it take for a cell to become cancerous
6 DNA mutations (enabling one active oncogene and disabling one tumor-suppressor gene)
operator
DNA segment that acts as a switch that is turned on or off, depending on whether a specific protein is bound there
default state
most genes in multicellular eukaryotes seems to be off
example of cell signaling
a cell can produce and secrete chemicals, such as hormones, that affect gene regulation in another cell
operon
a cluster of relates genes and sequences that control them
oncogene
a gene that causes cancer
for a proto-oncogene to become a oncogene
a mutation must occur in the cell's DNA
proto-oncogene
a normal gene with the potential to become an oncogene
repressor
a protein that binds to the operator and physically blocks the attachment of RNA polymerase to the promoter
DNA microarray process
a researcher collects all of the mRNA transcribed in a particular type of cell at any given moment
signal transduction pathway
a series of molecular changes that converts a signal received outside a cell to a specific response inside the target cell
what do the induced pluripotent stem cells represent
a single source of cells that could be used to replace those lost to damage or disease and hold promise in the field of regenerative medicine
DNA microarray
a slide with thousands of different kinds of single-stranded DNA fragments attached in a tightly spaced array (grid)
malignant tumor
a tumor that has the potential to spread
normal cell growth
a tumor-suppressor gene normally codes for a protein that inhibits cell growth and division. such genes help prevent cancerous tumors from arising or spreading
reverse transcripatse
a viral enzyme that produces DNA that is complementary to each mRNA sequence
repressor in bacterial operons
amino acid activates the repressor
inherited cancer
an individual inheriting an oncogene or a mutant version of a tumor-suppressor gene is one step closer to accumulating the mutations for cancer to develop
embryonic stem cells
are obtained by removing cells from an early embryo and growing them in laboratory culture
colon cancer
begins when an oncogene arises through mutation, causing unusually frequent division of normal-looking cells in the colon lining
example of pluripotent
bone marrow stem cells
bacterium
can adjust its gene expression to changes in the environment
adult stem cells
can also replace some of the body's cells after birth due to damage and growth
what can cells with the same genetic information do
can develop into different types of cells through gene regulation
multipotent
can differentiate into a few cell types, but only those of a closely related family of cells
dividing of embryonic stem cells
can divide indefinitely, and under the right conditions can develop into a wide variety of different specialized cells
the second-leading cause of death (after heart disease)
cancer
carcrinogens
cancer causing agents found in the environment
totipotent
capable of giving rise to any cell type thereby possibly developing into a complete organism
a single microarray
carries DNA from thousands of genes
what other genes are involved in cancer
changes in genes whose products inhibit cell division
pluripotent
descended from totipotent stem cells with limited functions - capable of giving rise to several different cell types
discovery of induced pluripotent stem cells
discovered in 2006 by Shinya Yamanaka (Japan), which utilized a method to convert mature body cells back into stem cells using specific gene manipulation
example of totipotent
embryo cells
what does the pattern of glowing spots do
enables the researcher to determine which genes were being transcribed in the starting cells
how activators act
make it easier for RNA polymerase to bind to the promoter
gene regulation
mechanisms that turn on certain genes while other genes remain turned off
gene regulation in eukaryotic cells
more sophisticated. the pathway from gene to protein is long, with a number of points where the process can be turned on or off, speeded up or slowed down
selective breakdown of proteins
some proteins that trigger metabolic changes in cells are broken down with a few minutes or hours
what does regulating gene activity allow for
specialization of cells within the body
Complementary DNA (cDNA)
synthesized using nucleotides that have been modified to fluoresce (glow)
DNA packing
tends to prevent gene expression by preventing RNA polymerase and other transcription proteins from binding to the DNA
what do people speculate about embryonic stem cells
the ES cells may be used to replace cells damaged by spinal cord injuries or heart attacks
if a molecule in the cDNA mixture is complementary to a DNA fragment at a particular location on the grid
the cDNA molecules binds to it, becoming fixed there
miRNAs regulate what
the expression of one half of all human genes
Protein activation
the final opportunities for regulating gene expression occur after translation and other proteins require chemical modification before they become active
after the lactose is gone
the genes are turned off and the bacterium does not waste its energy producing the enzymes
tumor-suppressor genes
the proteins they encode normally help prevent uncontrolled cell growth
after unbound cDNA is rinsed away
the remaining cDNA glows in the microarray
why is the use of embryonic stem cells controversial
the removal of ES cells destroys the embryo
what happens in the new shape
the repressor cannot bind to the operator, and the operator switch remains on
promoter
the site where the enzyme RNA polymerase attaches and initiates transcription of the genes for lactose-digesting enzymes
the lactose operon
the three lactose-digesting genes are adjacent in the DNA and turned off as a single unit. the regulation is achieved through short stretches of DNA that turn all three genes on and off at once, coordinating their expression
gene regulation in bacteria
there will be a rush of the sugar lactose. The E coli will express three genes for enzymes that enable the bacterium to absorb and digest the sugar
important roles for miRNAs
they can bind to complementary sequences on mRNA molecules in the cytoplasm. after binding miRNAs trigger breakdown of their target miRNA, whereas others block translation
most intriguing use of reproductive cloning
to restock populations of endangered animals
all three lactose enzymes are produced by what process
translation
induced pluripotent stem cells
type of pluripotent stem cell that can be generated directly from a somatic cell
most potent carcinogen
ultraviolet radiation (UV)
uncontrolled cell growth (cancer)
when a mutation in a tumor-suppressor gene makes its protein defective, cells that are usually under the control of the normal protein may divide excessively, forming a tumor
when is lactose present
when the operon is in "on" mode
what do both the operator and protein determine together
whether RNA polymerase can attach to the promoter and start transcribing genes
what can researchers learn from DNA microarray process
which genes are active in different tissues, at different times, or in tissues from individuals in different states of health