Most scientists subscribe to the theory of endosymbiosis to explain the presence of mitochondria in eukaryotic cells. According to the theory of endosymbiosis, early pre-eukaryotic cells phagocytosed free living prokaryotes, but failed to digest them. As a result, these prokaryotes remained in residence in the pre-eukaryotes, and continued to generate energy. The host cells were able to use this energy to gain a selective advantage over their competitors, and eventually the energy-producing prokaryotes became mitochondria.

In many ways, mitochondria are different from other cellular organelles, and these differences puzzled scientists for many years. The theory of endosymbiosis concisely explains a number of these observations about mitochondria. Perhaps most of all, the theory explains why aerobic metabolism is entirely limited to this one organelle, while other kinds of metabolism are more distributed in the cellular cytosol.

Cells with abnormalities in critical systems, such as mitochondria, will often undergo apoptosis. Which of the following is true of apoptosis?

Which of the following are common occurances in apoptosis that are not seen during necrosis?

I. Membrane blebbing

II. DNA fragmentation

III. Cell shrinkage

There are two models for the operation of the Golgi apparatus in eukaryotic cells. As it is difficult to visualize the operation of cells at the molecular level in real time, scientists typically rely on static electron micrographs to see the morphology of organelles. As a result, the dynamic operation of these organelles can sometimes be unclear.

Cisternal Maturation Hypothesis

In the cisternal maturation hypothesis, the cisternae of the Golgi apparatus evolve. Proteins leave the endoplasmic reticulum, and enter the cis-Golgi. The cisterna of the cis-Golgi then matures, with its enzymatic contents and internal environment changing as it becomes the medial-Golgi, and, eventually, the trans-Golgi.

In this model, the proteins never physically leave their membrane-bound cisternae during their transit across the Golgi. Instead, the entire unit of contents remains within the evolving cisternae.

Vesicular Transport Hypothesis

In contrast to the cisternal maturation hypothesis, the vesicular transport hypothesis posits that the cis-, medial-, and trans-Golgi cisternae are more static structures. Instead of evolving around their contents, the contents are physically shuttled via vesicular intermediates from each cisterna to the next.

In the case of vesicular transport, vesicles are shuttled along microtubules. Motor proteins facilitate this movement, with unique proteins being used for each direction of movement along a microtubule.

The Golgi apparatus has been implicated in cell death pathways. A scientist finds that a cell death pathway involving the Golgi is used in the breakdown of extra skin between digits during embryonic development. This pathway __________.

Apoptosis can be induced by mitochondria via the release of which protein from the mitochondrial inner membrane? 

An important part of creating DNA primers when performing a PCR or other quantitative analysis is the melting point of the primer.  Which set of primers would most likely work well together as the forward and reverse primers of a PCR?

Which piece of DNA has the lowest melting point?

Note: only one strand is shown

The principal chemical component of chromosomes is nucleic acid, though proteins are also important elements. Which of the following is true of nucleic acids?

Pick the reason that is least likely to explain why two purines will never be seen attached to each other in a DNA helix.

Which segment of DNA would have the highest melting point when paired with its complimentary strand?

Which of the following options include degenerate codons?