Prelim 3

lecture 14-18

Most frequently studied model organism for model vertebrate?

Zebrafish, their embryos are transparent and develop outside the mother, easy to observe stages

What did the early studies of Drosophila melanogaster show?

Genes are carried on chromosomes. Researchers observed that genes gontrolling eye color were inherited on the sex chromosome that determined male and female

most common plant model used by scientists

Arabidopsis.

Why do scientists study yeast?

because they carry out all of the basic tasks that a eukaryotic cell must perform, and they are closely related to animals as they are plants. while they may be easy to geneticlly manipulate, yeasts are eukaryotic and therefore have very defined nuclei that contain cellular DNA

What explains plants having more protein coding genes than fruit flies

PLants have genes that were duplicated during evolution, and thus their protein coding gene number is higher. repeated noncoding sequences cannot explain this observation, since these do not get counted in the number of protein coding genes

if a gene sequence is highly similar to the sequence in another organism it is called..

Gene sequences from one organism can be compared to another organism to see if they are homologous. Homology between genes (and thus their protein products) strongly suggest that they evolved from a common ancestral gene

A segment of DNA in the genome that is not a protein coding gene

Can be used to regulate gene activity. The genome of a complex organism is made up of protein coding genes, sequences that encode functional RNAs, and regulatory sequences used to finely tune gene activity. Other DNA noncoding sequences seem to be unimportant to the cell, but we might just not understand their function yet

The genome of the bacterium E.coli contains 4.6 (4.6 × 10^6) million nucleotide pairs, whereas the human genom contains some 3200 × 10^6 nucleotide pairs. what can be concluded based on these numbers

cannot conclude; cell size, number of genes, complexity of life, how many cells

component that associates with Cas9 protein

Cas9 protein along with guide rna

how can methods such as RNA interference or CRISPR be used to asses the role of a protein in cell signaling

they can eliminate the pathway of a gene by rna interference or CRISPR can reveal whether that gene participates in a particular signaling pathway

When cells respond to an extracellular signal, they most often convert the information carried by this molecule from one form to another. what is this process called

Signal transduction begins when the receptor on a target cell receives an incoming extracellular signal and then produces intracellular signaling molecules that altar cell behavior

when the hormone insulin is released into the bloodstream, what form of cell-cell signaling is being used?

endocrine signaling, part of the pancreas, for example, is an endocrine gland that produces several hormones, including insulin, which regulates glucose uptake in cells over the body

Many of the extracellular signal molecules that regulate inflammation are released locally at the site of infection. what form of cell-cell signaling is being used

paracrine. the extracellular signaling molecule acts as a local mediator on cells located nearby the signaling cell that produced it

what does a target cell require to respond to an extracellular signal molecule

a target cell does not need to be able to produce and secrete a signal molecule to which it will respond. instead, it must be exposed to that molecule and possess the correct combination of receptors, intracellular signaling pathways, and effector proteins to engage in the appropriate response

What is true about signaling

small molecules like acetylcholine, ex, usually bind to a pocket formed by an amino acids from several transmembrane segments of the receptor. these amino acids form noncovalent interactions with the signal molecule, allowing the receptor to recognize and bind specifically to its signal

what makes it possible for a combination of signal molecules to evoke a response that differs from the sum of the effects that each signal could trigger on its own

A cell can integrate and tailor its response to a combination of signals in part because the intracellular relay systems activated by the different signals interact. thus, the presence of one signal will often modify the effects of another

most extracellular signal molecules act on cell surface receptors rather than intracellular receptor. what is true about those extracellular molecules

molecules that are small or hydrophobic enough to pass through enough can pass through the plasma membrane and enter the cytosol of the target cell, where they can bind to intracellular receptors;

• they are too hydrophilic to pass directly across the plasma membrane

• they are too large to pass directly across the membrane.

under what condition will a target cell always respond quickly to an extracellular signal

changes in gene expression or the

researchers assayed the activity of enzyme F in three different types of tissue from the same mouse by determining the amount of enzyme product produced per milligram of tissue per unit time. As shown in the graph below, results indicate more product generation in the liver compared to the kidney and muscle samples

1. Differences in the translation of the mRNA encoding the protein among the tissue types

2. Differences in the post translational modifications of the enzyme among the tissue types Differences

3. Differences in the transcription of the gene encoding the enzyme among the tissue types

A cell that is specialized can return to its other forms, it is not fixed

true

Calls can respond to signals from

internal and external stimuli in order to change its gene expression

What is true about the differences between liver cells and kidney cells (within the same organism)

1. They contain different proteins

2. They contain the entire set of instructions needed to form the whole organism

3. They express different genes

Which molecule performs the primary signal transduction step in cell signaling

The CELL SURFACE RECEPTOR protein recognizes an extracellular signal and generates new intracellular signals in response

Positive feedback;

positive feedback regulation can generate an abrupt all or none response in which the cell moves from ignoring a signal to responding to it very strongly

What type of receptors to steroid hormones generally emply

Nuclear receptors

What are small intracellular signaling molecules often called

second messengers (and first messengers are extracellular)

signal integration

About 2% of approximately 19000 protein coding genes encode kinases; moreover, hundreds of distinct types of protein kinases are thought to be present in a single mammalian cell. These kinases often phosphorylation and regulate— positively or negatively— components in other signaling pathways, in addition to components in their own pathway

False of signal integration

it reguläres the generation of small intracellular messenger molecules

It can only takes palce between receptors of the same class

It relies on pos and neg feedback amplifying and dampening signal

Takes places when a single, activated target protein delivers a signal to many downstream effectors

How can methods such as RNA interference or CRISPR be used to assess the role of a protein in cell signaling

They can be used to eliminate the activity of a gene by RNA interference or CRISPR can reveal whether that gene participates in a particular signaling

Long range cell signaling and uses hormone signals?

Endocrine system

Slowest cell response?

a change in gene expression

The first step in a signaling pathway that responds to a molecule that stays in the extracellular space is

Binding of the signal molecule to a receptor… Signaling pathways that are activated in response to an extracellular signal must begin with the signal molecule binding to the receptor, often a membrane protein. Then the signal can be relayed and amplified inside the cell to produce a cellular response like activation of h, gene expression etc

describes a negative feedback regulation

Negative feedback is when a product of a signaling pathway inhibits steps earlier in the pathway. This leads to a dampening of the response in response to strong activation. Hence negative feedback can help a pathway rapidly switch between on and off states.

Enzymes called kinases add a phosphate to a protein; the phosphate could either activate or inactivate the protein, depending on the protein. Phosphotases remove phosphates

Steroid hormones trigger transcription of target genes by

binding to nuclear receptors that act as transcription factors for specific genes