DAT Question of the Day

Correct Answer: E. Haversian canals

Innervated refers to the structure having nerves and blood vessels that run through it. Nails and hair are consider dead/dying cells and would not have blood vessels that run through the exterior nail structure. Cartilage is not innervated which attributes to the long healing time of sprained joints. Osteoclasts are cells that help to break down bone cells and these cells themselves do not have blood vessels or nerves. The Haversian canals are a network of opening in the bone that allow for nerves and blood vessels to weave in and out of the bone.

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Correct Answer: C. competitive inhibitor

If the particle can bind to the active site, it is competing for the active site with the substrate. A non-competitive inhibitor would bind to an allosteric site on the enzyme, causing a conformational change to the active site, preventing the substrate from binding. Positive and negative inhibitors are terms that do not exist in biology.

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Correct Answer: C. Complete Dominance

Both of the brothers are phenotypically identical in regards to their hair texture. Genotypically, the two are different, as one is homozygous dominant and the other is heterozygous for hair texture. Despite the genotype differences the brothers are phenotypically similar with their hair texture because the dominant allele is the one being expressed. In both the case of Hh and HH, the presence of the dominant allele results in straight hair. This is due to complete dominance. In incomplete dominance, the heterozygote phenotypically is a hybrid between the two parents (i.e. a red and white flower make a pink flower). Whereas with codominance the heterozygote is phenotypically like both parents, i.e. red and white flower makes white plant with red spots. Law of independent assortment and law of segregation refer to Mendelian genetics, but are not the explanations for the phenotypic similarity between the two genotypes.

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Correct Answer: C. Salt glands secrete the excess salt.

This is a great DAT comprehension question. Let’s run through the answer choices and see what we can eliminate. Choice [A] is wrong because there is no structure in the intestine that can physically eliminate salt. Choice [B] is wrong because most chordates have similar osmolarities. Choice [D] is incorrect because nephrons become longer to resorb MORE ions and water, not less. A classic example are rodents in the desert that have very long loops of Henle to resorb as much water and ions as possible. Lastly, specialized bacteria will still eliminate the salts after they’ve used them, so it does not solve the problem of excessive salt. Choice [C] is correct, sea birds have supraorbital glands, or salt glands, above their eyes, which secrete excess salt from their blood. It functions similar to a kidney, but is much more efficient at excreting salt.

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Correct Answer: B. Transport proteins are often used by many substrates while channel proteins are generally used by ions.

Both of these types of proteins have a large variety in their shapes, sizes, and complexities. Therefore, no generalization can be made about them, and [C], [D], and [E] can be eliminated. Many transport proteins can use passive transport as well via uniport, for example, so [A] can be eliminated too. This leaves [B], where it states that channel proteins are used generally by ions. They aren’t called “ion channels” for nothing!

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Correct Answer: C. methylation.

The bacterial DNA contains numerous methylated adenines and cytosines. This methylation allows restriction endonucleases to discriminate between the host and viral DNA. Bacterial DNA don’t have nucleosomes and don’t coil.

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Correct Answer: E. Merkel cells.

Merkel cells are oval shaped and usually can be found in clusters under ridged epidermal areas. These are the cells responsible for fine-touch differentiation. Keratinocytes produce keratin and are the cells responsible for creating the skin barrier against infection. Fibroblasts manufacture collagen and are found in the dermal layer since collagen is one of the connective tissues. Melanin, the pigment responsible for skin color, is produced by melanocytes. The function of the Langerhans’ cell is to fight against skin infection by processing microbial antigens.

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Correct Answer: A. NADH and FADH2 are oxidized, hydrogen ions move into the intermembrane space, ATP is generated.

In animal cells the electron transport chain (commonly referred to as the ETC) is instrumental in cellular respiration. During the ETC, the two energy carriers, NADH and FADH2, are oxidized. Their electrons are transferred to the cytochromes embedded in the intermembrane of the mitochondria. As the electrons “jump” along the ETC, hydrogen ions are pumped out of the matrix into the intermembrane space. As a result of the hydrogen ion gradient (an electrochemical gradient), the hydrogen ions move through the ATP synthase out of the intermembrane space back into the matrix, thereby making ATP for the cell. The only answer option that details this process accurately is [A]. Note: NADPH, is an energy carrier in photosynthesis. You can think that the “P” is for plants to help remember, but it is really for phosphorus.

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Correct Answer: D. Stimulate sodium reabsorption by the kidneys.

When the adrenal cortex secretes glucocorticoids, many actions are initiated. Cortisol, for example, is released during times of stress. Gluconeogenesis (the process of creating glucose from non-carbohydrates) and lipolysis (the breakdown of fats) are both activated to generate more energy for the both during times of stress. Immunologic response, inflammatory response, glucose uptake by muscle and fat tissues, and protein construction are all restricted as these are energetically expensive and the body needs to place its energy reserves into other areas. Sodium reabsorption by the kidneys is regulated by secretion of mineralocorticoids of the adrenal cortex, such as aldosterone.

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