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