Biology Chapter 11 (Gene Regulation)

Embryonic stem cells (ES cells)

cells in mammals which are obtained by removing cells from an early embryo and growing them in a laboratory culture

In the umbilical cord and placenta ES cells are...

partially differentiated

Gene regulation was first discovered in...

prokaryotes (because it is the method bacteria utilize to regulate genes)

Flaws of human cloning

extremely difficult and inefficient, only a small percent develop normally and they appear to be more unhealthy, ethically unsure

Applications of reproductive cloning

farm animals: cloning a specific set of desirable traits produces identical herds research: identical herds provide control groups for experiments medicine: human organs in animals could become life-saving transplants

What do cells use for the long term inactivation of genes?

gene packing

Lifetime of mRNA

highly variable: ranging from hours to weeks to months

Consequence of X chromosome inactivation

if a female has differed versions of a gene on each of her X chromosomes, about half of her cells will express one version, while the other half will express the alternate version

X chromosome inactivation

in female mammals, one X chromosome in each somatic cell is highly compacted and almost entirely inactive (this first takes place early in embryonic development when one of the two X chromosomes in each cell is inactivated at random/after that one X chromosome is inactivated in each embryonic cell, all the cells descendants will have the same X chromosome turned off)

Conclusions from reproductive cloning at the Frozen Zoo

it is possible to produce a baby even when a female donor species is unavailable

RNA interference

new technology designed to attempt to exploit the miRNAs through the injection of small RNA molecules into a cell to turn off specific genes

The selective breakdown of proteins

occurs after translation and allows a cell to adjust to the kinds and the amounts of the proteins in response to changes in the environment (some proteins that trigger metabolic changes in cells are broken down within a few minutes or hours)

Colon cancer

one of the best understood types of human cancers (strikes nearly 150,000 Americans)

Example of a plant for which cling is its only method of reproduction

orchid

Gene packing

prevents gene expression by preventing RNA polymerase and other transcription proteins

Restriction enzymes

proteins that recognize DNA and cut it at specific sequences

Growth factors

proteins that stimulate cell division (for other factors that affect the cell cycle)

Activators

proteins that turn genes on by binding to DNA (more common than repressor proteins that turn genes off

Vetangs

put into cow eggs to clone them when they became nearly extinct form Indonesia

Example of gene regulation during the process of translation

red blood cells have a protein that prevents the translation of hemoglobin mRNA unless the cell has a supply of heme, an iron-containing chemical group essential for hemoglobin function

Reproductive cloning

results in the birth of a new animal by prompting further development by implanting the early embryo into the uterus of a surrogate mother

For which types of plants is cloning the sole means of mass production?

seedless plants which cannot reproduce sexually

Homeotic genes are _____________ in every eukaryotic organism

similar

Why are BRCA 1 and BRCA 2 considered tumor suppressors?

the normal versions protect against breast cancer

Gene expression

the overall process by which genetic information flows from genes to proteins

Nuclear transplantation

the procedure used to perform animal cloning which was first performed in the 1950s on frog embryos (involves replacing the nucleus of an egg cell or a zygote with a nucleus removed from an adult body cell) later, repeated division forms

Where were microRNAs discovered?

(accidentally) in petunias

Steps in the progression of colon cancer...

1. ... 2. ... 3. ...

Transcription is turned off in the (lac) operon

1. a protein called a repressor binds to the operator 2. the protein physically blocks the attachment of RNA polymerase to the promoter 3. ...

How are microarrays used?

1. mRNA is isolated 2. mRNA is combined with reverse transcriptase 3. the reverse transcriptase produces DNA completely complementary to the mRNA referred to as cDNA (the cDNA is synthesized using nucleotides which have been modified to to fluoresce, so the glowing cDNA represents the genes that have been actively transcribed) 4. a small amount of the fluorescent cDNA is added to the DNA in the microarray. if a molecule in the cDNA mixture is complementary to a DNA fragment in the grid, the cDNA molecule binds and becomes fixed there. 5.once the unbound cDNA is rinsed away, the remaining cDNA glows in the microarray (the pattern of glowing lights shows which genes are being transcribed in the starting cells)

Process of reproductive cloning from the Frozen Zoo

1. scientists implant nuclei from the frozen cells into nucleus-free eggs from dairy cows 2. embryos are implanted into surrogate cows 3. healthy baby bated is produced

Steps in cell-cell signaling when response is transcription

1. signaling cell secretes the signal molecule 2. molecule binds to a specific receptor protein embedded in the target cell's plasma membrane 3. binding activates a signal transduction pathway consisting of a series of relay proteins 4. relay molecule in the series activates a transcription factor 5. transcription factor triggers the transcription of a certain gene 6. translation of the mRNA produces a protein that can perform the function the signal originally called for

Transcription is turned on in the (lac) operon

1. the sugar interferes with the repressor to the operator by binding to it 2. the repressor's shape. in its new shape the repressor cannot bind to the operator and the operator switch remains on 3. RNA polymerase is no longer blocked, so it can now bind to the promoter 4. RNA polymerase transcribes the genes for the specific protein (example: lactase enzymes) 5. translation produces all 3 proteins (example: all 3 lactose enzymes)

What percent of DNA is actually coded for proteins?

1..5%

A typical human gene contains ________ exons

10 (nearly all genes are spliced at least two different ways and some are spliced hundred of different ways)

Mutations of which genes are commonly found in inherited breast cancers?

BRCA 1 and BRCA 2

CRISPR

Clustered Regularly Interspaced Short Palindromic Repeats genetic loci in bacteria that contain many short repeated sequences with short intervening sequences of exogenous DNA (derived from foreign bacteriophages or plasmids). the system acts as a prokaryotic 'immune system' resisting exposure to these exogenous DNA sequences and those that resemble them

Supercoiling

DNA is so tightly wound around histone proteins that polymerase cannot fit and mRNA is not produced

Enhancers

DNA sequences which are bond to the promoter and transcription factors (sequences of DNA that tells genes to turn on or off)

Silencer

DNA sequences which inhibit the start of transcription

An infusion of umbilical cord blood stem cells shows the potential to cure...

Krabbe disease

Operator

a DNA segment between the promoter and the enzyme genes which acts as the switch that is turned on or off depending on whether a specific protein is bound there.

Operon

a cluster of related genes and sequences in a prokaryote that control them by turning them on and off to regulate their expression (includes a promoter, operator, and the genes that make proteins)

All body cells contain...

a complete complement of genes, even if they do no express all of them

BPDE

a component of tobacco smoke which was added to human lung cells growing in a lab. scientists found that the BPDE binds to a gene within the cells called p53, which helps suppress the growth of tumors. BPDE caused mutations in the p53 gene that deactivated the protein for suppressing tumor and therefore allowed tumors to grow.

"The Frozen Zoo"

a facility in San Diego, CA which stores samples of rare endangered animals for conservation

Oncogene

a gene that causes cancer

What must occur for a porto-oncogene to become an oncogene?

a mutation in the cell's DNA

Proto-oncogene

a normal, healthy gene that has the potential to become an oncogene if altered

Repressor

a protein that binds to the operator and physically blocks the attachment of the RNA polymerase

CRISPR cast-9

a restriction enzyme that snips DNA

Signal transduction pathway

a series of molecular changes that converts a signal received outside a cell to a specific response inside the target cell (initiated by a signal molecule binding to a receptor protein)

First mammal cloned from an adult cell

a sheep named Dolly (1996) (resembled the nucleus donor, not the egg donor of the surrogate mother)

DNA microarray

a slide with thousands of different kinds of single-stranded DNA fragments attached in a tightly spaced array (each DNA fragment is obtained from a particular gene so a microarray carries DNA from thousands of genes

Adult stem cells from bone marrow are used as...

a source of immune system cells

Human papillomavirus (HPV)

a virus that harbors cancer-causing genes which can be transmitted through sexual contact (associated with cancers such as cervical)

Alternative RNA splicing

allows an organism to produce more than one type of polypeptide from a single gene exon splicing which generates different mRNA molecules form the same starting RNA molecule

Adult stem cells

although they are further along the road of differentiation, they can generate replacements for some of the body cells (though in less variety than ES cells)

Barbody

another word for an inactive form of a chromosome

Why are aren't adult stem cells ethically problematic?

because no embryonic tissue is allowed in their harvest

Source of stem cells (other than embryo)

blood collected from umbilical cord and placenta at birth

All mRNAs are eventually...

broken down and their parts are recycled

Abilities of embryonic stem cells

can divide indefinitely and develop into a variety of specialized cells

Carcinogens

cancer-causing agents found in the environment

Mechanisms of enzymes that control amino acid synthesis

cause bacteria to stop making these molecules when they are already present in the environment in order to save materials and energy for the cell (amino acid activates the repressor)

Therapeutic cloning

cloning to produce embryonic stem cells`

Nucleosome

composed of a short length of DNA wrapped around a core of 8 histone proteins (linkers are in between them)

Gene regulation in multi-cellular organisms...

crosses cell boundaries

When is cell signaling most important?

during early embryonic development

Tumor-suppresor genes

encode for proteins that normally help prevent uncontrolled cell growth (therefore, changes in these genes are involved in cancer)

Transcription factors

many proteins involved with transcriptional regulation in eukaryotes and acting in concert to bind enhancers and to the promoter

Homeotic genes

master control genes that regulate groups of other genes which will determine what body parts will develop in which location

Dangers of animal cloning

may detract from efforts to preserve natural habitats, genetic diversity does not increase, and cloned animals are less healthy than those produced via fertilization

Gene regulation

mechanisms that turn on certain genes while other genes remain turned off in order to allow different types of cells to develop from the same genetic information.

To produce a full-fledged cancer cell...

more than 1 mutation is needed (typically at least 6)

microRNAs

small single-stranded which can bind to complementary sequences on mRNA molecules in the cytoplasm (may regulate the expression of one half of all human genes) after binding: some trigger breakdown of their target mRNA while others block translation

Although some occur _____, most cancers arise from _____

spontaneously/mutations

Example of gene regulation after translation

the hormone insulin is synthesized as one long, inactive polypeptide that must be chopped into pieces before it becomes active

Regeneration

the regrowth of lost body parts ex: salamander

The methods eukaryotic cells use for gene regulation

the regulation of DNA packing, the invitation of transcription, RNA processing and breakdown, the initiation of translation, and protein activation and breakdown

Controversy over ES cells

the removal of the ES cell destroys the embryo

Promoter

the site where the enzyme RNA polymerase attaches and initiates transcription

Which bacteria cell does natural selection favor?

those that can conserve resources and energy by not squandering valuable resources to make nutrients from scratch when a nutrient is plentiful.

Repressible

transcription is typically in the "off" position but is capable of being turned off

Inducible

transcription is typically in the "on" position but is capable of being turned on

Example of a repressible gene

trp operon (typically on)