DAT Question of the Day

Correct Answer: C. Cellular slime molds

Bryophytes are a type of plant and can be eliminated. While the rest of the choices are unicellular protists, only cellular slime molds exhibit an amoeboid characteristic and “slug stage”, when many cells combine in a mass.

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Correct Answer: B. Golgi apparatus.

The Golgi apparatus is an organelle which somewhat resembles a stack of pita bread or pancakes. Its purpose is to modify proteins that are manufactured by the endoplasmic reticulum. Within the Golgi are resident enzymes, which catalyze the cargo proteins. The modification processes are glycosylation – the adding or removing of sugars from the protein, sulfation – addition of sulfate groups and phosphorylation – adding phosphate groups.

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Correct Answer: A. Prophase I

The process described is crossing over. Crossing over occurs during the first stage of meiosis called prophase I. In this stage the homologous chromosomes begin to come together and they form tetrads. The homologous chromosomes are able to “cross over” sections of the chromosome between the homologous pair. The point at which the new chromosomal pieces attach is referred to as the chiasmata.

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Correct Answer: B. Secondary Succession

Succession is the process that ecological areas go through to repopulate a community. Following a forest fire, the environment is beginning from the producers level and must first grow small grasses, then small shrubs, before consumers and higher-level consumers will repopulate the area. In the event of a volcano, this would be an example of primary succession, as there is no soil to sustain plants. Instead, bacteria populate the area, and eventually give rise to soil and plants and animals. Homeostasis refers to the internal regulation of an organism as opposed to the process an external environment goes through. Biological regeneration is a distractor answer choice testing your true knowledge of the topic at hand.

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Correct Answer: D. DNA polymerases require a primer base-paired to the template and with a free 3′-end.

DNA polymerase can add dNTPs (deoxynucleoside triphosphates) only to a pre-existing oligonucleotide chain that is annealed to the template DNA. The enzyme adds dNTPs on a free 3′-OH- group. Primers in replication are RNA based. These primers are then cut out via endonuclease activity and replaced with DNA nucleotides. Finally, DNA ligase fuses the gap between the fragments of DNA.

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Correct Answer: A. Testes

This is a great example of a conceptual question on the DAT. There are many pieces of information here, but if we take it one step at a time, it really isn’t that bad.

First, we have to explain why Cell Type 2 has such a low intracellular concentration compared to the other Cell Types. Recall that steroid hormones are lipid-soluble, which means they freely diffuse through the cell membrane.

In contrast, peptide hormones are stored in granules and are only released when stimulated. So from this information, we can deduce that Cell Type 2 must be synthesizing a steroid hormone, and the other Cell Types must be a variant of a peptide hormone.

As Cell Type 2 was synthesizing its steroid hormone, it was just freely diffusing out, and not building up in concentration inside the cell, so when the researcher measured the intracellular concentration, she barely found any steroid hormone at all. In contrast, Cell Type’s 1, 3, 4, and 5 were synthesizing peptide hormones and building up their concentrations because they store peptide hormones in granules.

Lastly, the question asks where Cell Type 2 possibly came from. Cell Type 2 would need to be harvested from a part of the body that produces steroids, of which there are three main centers, and those are:

1. Adrenal cortex, which produces mineralocorticoids and glucocorticoids like aldosterone and cortisol. It also is a secondary site for androgen synthesis.

2. Testes, which mainly secrete testosterone in relation to hormone synthesis.

3. Ovaries, which mainly secrete estrogen and progesterone in relation to hormone synthesis.

Note: The placenta also produces steroid hormones during pregnancy.

Thus, the correct answer to this question is [A], the testes, as it is the only organ listed that synthesizes steroid hormones.
All of the other answer choices describe organs that do not produce steroid hormones, and are therefore incorrect.

B. Adrenal medulla – Composed mainly of chromaffin cells, which synthesize catecholamines (epinephrine, norepinephrine, and dopamine) from tyrosine.

C. Anterior pituitary – Produces FSH, LH, ACTH, TSH, Prolactin and GH. (Remember the acronym FLAT PiG).

D. Pineal gland – The pineal gland is responsible for synthesizing melatonin.

E. Pancreas – Synthesizes several important peptide hormones, including insulin, glucagon, and somatostatin.

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Correct Answer: C. prevents glucose from leaking through the plasma membrane.

Glycolysis takes place in the cytosol. It is a characteristic of eukaryotic and prokaryotic cells. The first reaction of glycolysis is irreversible since it requires an energy investment. Glucose-6-phosphate cannot pass back through the plasma membrane.

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Correct Answer: E. Both A and D.

The correct answer is E. Bacteria utilize a pillus for conjugation, in order to exchange genetic material. The lambdaphage viral vector can be used injecting a specific sequence of DNA into a target cell, but not for encouraging the cell to uptake plasmid DNA. Electroporation involves using a small charge to cause the cell membrane to become more porous and uptake the plasmid. Heat shock involves heating up the target cells to ~42ºC after keeping them on ice in the presence of CaCl2, the cell membranes will become more porous and uptake the plasmid as with electroporation.

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