Bio chapter 11

plant cloning is now used extensively in

agriculture

If a female has different versions of a gene on each of her x chromosomes,

About half of her cells will express one version, while the otehr alf will express the alternate version

If you drink a milk shake there will be a sudden rush of the sugar lactose. In response, E. Coli will express three genes for enzymes that enable the bacterium to absorb and digest this sugar. After the lactose is gone, these genes are turned off

Such regulation is at the heart of metabolism, the chemical reactions that transform energy and matter within all cells

X chromosome inactivation occurs in female mammals,

Takes place early in embryonic development, and is when one of the two X chromosomes in each cell is inactivated at random

RNA processing includes

The addition of a cap and tail, the removal of introns(noncoding DNA segments that interrupt the genetic message), and RNA splicing(the splicing together of exons)

Phase 1

The body along major axes

When these genes are mutated

The proteins malfunction and cell may become cancerous

Repressor proteins, which may bind to DNA sequences called silencers

Inhibit the start of transcription

Lac operon in "on" mode

Lactose is present

tumor suppressor gene

A gene whose protein products inhibit cell division, thereby preventing uncontrolled cell growth (cancer).

A signal molecule can act by binding to a receptor protein and initiating a signal transduction pathway,

A series of molecular changes that converts a signal received outside a cell to a specific response inside the target cell

After one xx chromosome is inactivated in each embroynic cell,

All of that cell's descendants will have the same x chromosome turned off

In the lac operon, when the operator switch is turned on,

All the enzymes needed to metabolize lactose are made at once

Within a cell, exon splicing can occur in more than one way, generating different mRNA molecules fro the same starting RNA molecule. With _________________, an organism can produce more than one type of polypeptide from a single gene

Alternative RNA splicing

Genes determine the nucleotide sequence of specific mRNA molecules,

And mRNA in turn determines the sequence of amino acids in proteins

Small single stranded RNA molecules, called microRNAs(miRNAs), can

Bind to complementary sequences on mRNA molecules

Within a multicellular organism, information must be communicated within

Cells

The cells in you body are specialized in structure and function. How do cells develop differently from one another

Cells with the sam genetic information can develop into different types of cells through gene regulation, mechanisms that turn on certain genes while other genes remain turned off. Regulating gene activity allows for specialization of cells within the body

Transcriptional regulation in eukaryotes is complex, typically involving many proteins,

Collectively called transcription factors, acting together to bind to DNA sequences called enhances and the promot

After an mRNA is produced in its final form, its lifetime can be highly variable, fro hours to weeks to months

Controlling the timing of mRNA breakdown provides another opportunity for regulation. But all mRNAs are eventually broken down and their parts recycled

Interactions between the cells of an embryo through chemical signals

Coordinate development

scientists who study gene regulation often want to determine which genes are active in tissues. rather than studying just one gene, researchers can study many or even all genes at once using

DNA microarrays

Phase 4

Differentiated

Many operons have been identified in bacteria. Some are quite similar to the lac operon, whereas others have different mechanisms of control

For example, operons that control amino acid synthesis cause bacteria to stop making these molecules when they are already present in the environment, saving materials and energy. In these case, the amino acid activates the repressor.

A significant amount of the genome is trancribed into

Functioning but nonprotein coding RNAs

Every cell in your body has the same DNA as the zygote and every somatic cell contains every

Gene

A gene that is turned on is being transcribed and translated into specific proteins. The overall process by which genetic information flows from genes to proteins is called

Gene expression

For example, a cellcan produce and secrete chemicals, such as hormones, that afect

Gene regulation in other cells

The ability to regulate genes underlies all of life's processes, such as

Growth, metabolism, and the ability to adapt to a changing environment

Eukaryotes, especially multicellular ones,

Have more sophisticated mechanisms than bacteria for regulating the expression of their genes

If a woman's breast cancer is treated in its earliest stages

Her chance of surviving fie years or more is nearly 100%

If her breast cancer is not treated until it has spread throughout her body

Her five year survival rate is less than 25%

Pattn formation in animals occurs in 4 phaess controlled by

Hierarchy or transcription factors

Treatment typically involves surgery, followed by ________ __________and ____________ to kill cancer cells

Hormone therapy, radiation

Cells may use DNA packing for

Long term inactivation of genes

Lac operon in "off" mode

No lactose available, transcription turned ff because a protein called a repressor binds to the operator and physically blocks the attachment of RNA polymerase to the promoter

Between the promoter and the enzyme genes, a DNA segment called an

Operator acts as a switch that is turned on or off, depending on whether a specific protein is bound there

Such a cluster of related genes and sequences that control them is called an

Operon.(lac operon)

For example, the hormone insulin must be chopped into pieces before it comes active.

Other proteins require chemical modification before they become active. The selective breakdown of proteins allows cells to adjust the kinds and amounts of its protein

Phase 3

Particular body parts

How do DNA control sequences turn genes on and off?

Promoter(one control sequence) is the site where the enzyme RNA polymerase attaches and initiates transcription

The DNA protein assembly

Promotes the binding of RNA polymerase to the promoter

Repressor proteins that turn genes off are less common in eukaryotes than activators,

Proteins that turn genes on by binding to DNA. Activators act by making it easier for RNA polymerase to bind to the promoter

Many cancer associated genes encode

Proteins that turn other genes on or off

The pathway from gene to protein in eukaryotic cells is a long one,

Providing a number of points where the process can be turned on or off, speeded up or slowed down

Master control genes called homeotic genes

Regulate groups of other genes that determine what body parts will develop in which locations. Similar homeotic genes direct early development in nearly every eukaryotic organism examined. Mutations in homeotic genes can produce bizarre effects

In addition to microRNAs, there is another class of small RNA molecules called

Small interfering RNAs(siRNAs.) the blocking of gene expression by siRNAs is called RNA interference(RNAi)

Phase 2

Segmentation

The initiation of transcription is

The most important stage for regulating gene expression

Every cell in your body was produced through successive rounds of mitosis starting from the zygote

The original cell that formed after fusion of sperm and egg

How does the presence or absence of lactose influence the activity of the genes that code for the lactose enzymes

Three lactose digesting genes are adjacent in the DnA and turned on and off as a single unit. The regulation is achieved through short stretches of DNA that help turn all three genes on and off at once.

The final opportunities for regulating gene expression occur after

Translation

Cell to cell signaling and the control of gene expression are particularly important during early embryonic development,

When a single celled zygote develops into a multicellular organism

Within a eukaryotic cell, transcription occurs in the nucleus,

Where RNA transcripts are processed into mRNA before moving to the cytoplasm for translation by the ribosome

The operator and protein together determine

Whether RNA polymerase can attach to the promoter and start transcribing the genes

The process of translation,

Which an mRNA is used to make a protein, offers additional opportunity for control by regulatory molecules

Scientists can now tell

Which genes are mutated in a given tumor

Natural selection has favored bacteria that express only the genes

Whose products are needed by the cell

The default state for most genes in multicellular eukaryotes seems to be off,

With the exception of housekeeping genes for routine activities such as the digestion of glucose

oncogene

a gene that causes cancer

proto oncogene

a normal gene with the potential to become an oncogene

a cell can acquire oncogene from

a virus or mutation of one of its own proto oncogenes

cord blood stem cells

appear to cure babies of Krabbe's disease, a fatal inherited disorder of nervous system, and have been used as treatment for leukemia

embryonic stem cells can divide indefinitely and

can develop into a wide variety of specialized cells

most cancers arise from mutations that are caused by carcinogens

cancer causing agents found in the environment, including ultraviolet radiation and tobacco products

when a salamander loses a tail

certain cells in the tail stump reverse their differentiated state, divide, then differentiate again to give rise to a new tail

gene regulation affects

cloning and cancer

development of malignmant tumor is accompanied by a gradual accumulation of mutations that

convert proto oncogenes to oncogenes and knock out tumor suppressor genes

cloning may create problems such as

detract from efforts to preserve natural habitat, does not increase genetic diversity, not as beneficial to endangered species as natural reproduction

the drospophila embryo is subdivided into 15 segments,

each of which gives rise to unique structures in the adult

all body cells contain a complete complement of genes

even if theyare not expressing all of them

adult stem cells are

further along the road to differentiation than ES cells, can therefore give rise to only a few related types of specialized cells, can also generate replacement for some of body's cells

homeotic genes

genes that specift the fate of a particular segment or region of the body

colon cancer

gradual process, produced by more than one mutation

DNA microarray

is a glass slide with many tiny wells, each containing a different fragment of single stranded DNA that derives from a particular gene

Often, the cDNAs from two samples are labled with

molecules that emit different colors and tested on the same microarray

the purpose of therapeutic cloning is

not to produce a living organism but rather to produce embryonic stem cells

many proto oncogenes code for growth factors,

proteins that stimulate cell division, or for other proteins that affect cell cycle

regeneration

regrowth of lost body parts

in mammals, embryonic stem cells are obtained by

removing cells from several day old embryo and growing them in laboratory culture

nuclear transplantation involves

replacing the nucleus of an egg cell or zygote with nucleus removed from adult body cell

fate

the ultimate morphological features that a cell or group of cells adopts

a single differentiated plant cell can

undergo cell division and give rise to a complete adult plant