In the crusade to create a vaccine for Poliomyelitis, Jonas Salk and Albert Sabin created two separate vaccines that proved to be successful in preventing Polio onset.

The Salk vaccine, which is given by standard injection, contained virus particles inactivated by an organic solvent. This method has the advantage of inactivating each of the three Polio strains with no bias.

Albert Sabin's vaccine, given by oral inoculation via sugar water, contained live virus particles that had been genetically attenuated. With this method, each of the three Polio strains acquired separate mutations that made them unable to infect the human host cells. Strain 2 in particular contained one single nucleotide polymorphism in the internal ribosomal entry site (IRES) that prevented successful viral replication.

What is the function of the internal ribosomal entry site (IRES) utilized by the Poliovirus? 

Which of the following statements about translation is incorrect?

Type 1 diabetes is a well-understood autoimmune disease. Autoimmune diseases result from an immune system-mediated attack on one’s own body tissues. In normal development, an organ called the thymus introduces immune cells to the body’s normal proteins. This process is called negative selection, as those immune cells that recognize normal proteins are deleted. If cells evade this process, those that recognize normal proteins enter into circulation, where they can attack body tissues. The thymus is also important for activating T-cells that recognize foreign proteins.

As the figure below shows, immune cells typically originate in the bone marrow.  Some immune cells, called T-cells, then go to the thymus for negative selection. Those that survive negative selection, enter into general circulation to fight infection. Other cells, called B-cells, directly enter general circulation from the bone marrow. It is a breakdown in this carefully orchestrated process that leads to autoimmune disease, such as type 1 diabetes.

When activated, T-cells use a number of proteins to kill cells that they recognize as foreign. A scientist develops an experimental drug to treat autoimmune disease by disrupting one of these proteins. The drug degrades the cytosolic mRNA for this protein in a T-cell. Which of the following is true if this drug is used successfully?

I. The protein is synthesized, but in an inactive form

II. The protein gene is transcribed

III. The total complement tRNA used for synthesis of the protein is not mobilized to active ribosomes

Temperature sensitive (Ts) mutations are a powerful genetic tool in yeast and fruit flies. Ts mutations allow researchers to examine biological functions of specific genes at permissive (phenotypically normal) and restrictive (phenotypically abnormal) temperatures. What is the likely result of the Ts mutation at the restrictive temperature?

In 2013, scientists linked a cellular response called the unfolded protein response (UPR) to a series of neurodegenerative diseases, including such major health issues as Parkinson’s and Alzheimer’s Disease. According to their work, the unfolded protein response is a reduction in translation as a result of a series of enzymes that modify a translation initiation factor, eIF2, as below:

In the above sequence, the unfolded protein sensor binds to unfolded protein, such as the pathogenic amyloid-beta found in the brains of Alzheimer’s Disease patients. This sensor then phosphorylates PERK, or protein kinase RNA-like endoplasmic reticulum kinase. This leads to downstream effects on eIF2, inhibition of which represses translation. It is thought that symptoms of neurodegenerative disease may be a result of this reduced translation.

Which of the following is true of the process of translation discussed in the passage?

A surface protein would most likely be translated from mRNA by the __________.

Each of the following membrane transport processes requires the use of specific proteins that allow for movement across the plasma membrane EXCEPT __________.

The cell is the most basic functional unit of life.  Everything that we consider to be living is made up of cells, and while there are different kinds of cells, they all have some essential features that link them all together under the category of "life."  One of the most important parts of a cell is the membrane that surrounds it, seperating it from the rest of the environment.

While organisms from the three main domains live in incredibly different environments, they all possess similar cell membranes.  This phospholipid bilayer protects the cell, giving it a way to allow certain things in while keeping other things out.  Though organisms from different domains have different kinds of fatty linkages in their membranes, they all serve this essential purpose.

Membranes contain all kinds of essential proteins and signal molecules that allow the inside of the cell to respond to the outside of the cell.  In a multicellular eukaryote, this ability can be used to allow cells to communicate.  In a bacterial colony, an extracellular signal could be used to signal other bacteria.  Signals cascade through a series of molecular pathways that go from the outside of the cell all the way to the nucleus and back out again, giving the cell control on a genetic level.  This allows cellular responses to be quick and effective, and it also allows the cell to control how long it stays in that state.

One of the most important membrane proteins is the sodium-potassium pump. What would happen to a cell if this pump suddenly stopped working?

The sodium-potassium pump helps to maintain electrolyte gradients through use of ATP. Which of the following best describes this type of transport?

Assume that there are thirty sodium ions outside the cell and twenty potassium ions inside the cell. What will happen after one cycle of the sodium-potassium pump?