Human chromosomes are divided into two arms, a long q arm and a short p arm.  A karyotype is the organization of a human cell’s total genetic complement.  A typical karyotype is generated by ordering chromosome 1 to chromosome 23 in order of decreasing size. 

When viewing a karyotype, it can often become apparent that changes in chromosome number, arrangement, or structure are present.  Among the most common genetic changes are Robertsonian translocations, involving transposition of chromosomal material between long arms of certain chromosomes to form one derivative chromosome.  Chromosomes 14 and 21, for example, often undergo a Robertsonian translocation, as below.

A karyotype of this individual for chromosomes 14 and 21 would thus appear as follows:

Though an individual with aberrations such as a Robertsonian translocation may be phenotypically normal, they can generate gametes through meiosis that have atypical organizations of chromosomes, resulting in recurrent fetal abnormalities or miscarriages.

During mitosis and meiosis chromosomes are separated from homologous pairs at the metaphase plate. A disorder in which of the following proteins could be expected to produce an aberration in cell division?

Sexually transmitted diseases are a common problem among young people in the United States. One of the more common diseases is caused by the bacterium Neisseria gonorrhoeae, which leads to inflammation and purulent discharge in the male and female reproductive tracts.

The bacterium has a number of systems to evade host defenses. Upon infection, it uses pili to adhere to host epithelium. The bacterium also uses an enzyme, gonococcal sialyltransferase, to transfer a sialyic acid residue to a gonococcal surface lipooligosaccharide (LOS). A depiction of this can be seen in Figure 1. The sialyic acid residue mimics the protective capsule found on other bacterial species.

Once infection is established, Neisseria preferentially infects columnar epithelial cells in the female reproductive tract, and leads to a loss of cilia on these cells. Damage to the reproductive tract can result in pelvic inflammatory disease, which can complicate pregnancies later in the life of the woman.

A scientist discovers that Neisseria uses flagella to move between host cells. Which of the following is true of the flagella?

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.

Phagocytosis of the sort that was involved in endosymbiosis makes use of microtubules to orient the cell appropriately. Which of the following processes also directly uses microtubules?

Which of the following is true of microtubules?

Which of the following is not a function of microtubules?

What happens at the minus-end of actin filaments when the concentration of G-actin is above its critical concentration?

Actin is the major protein that composes which part of the cytoskeleton?

Which of the following structures that promote cell motility generates motion by sliding actin microfilaments?

Arp2/3 is a protein complex that helps nucleate branch points on __________ chains.

In which of the following structures do actin microfilaments play a crucial role?

I. Contractile ring formed during cytokinesis

II. Sarcomeres

III. Adherens junctions

IV. Eukaryotic flagella