DAT Question of the Day

Correct Answer: C. Estrogen

Follicle stimulating hormone causes the follicle in the ovary to begin to divide to complete meiosis II. The growing follicle that will eventually release the egg during ovulation secretes estrogen. The estrogen then spurs the secretion of luteinizing hormone by the anterior pituitary gland, causing the follicle to rupture and release the egg. It is the estrogen and progesterone that is responsible for readying the endometrium for implantation should fertilization occur.

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Correct Answer: C. Water is reabsorbed into the bloodstream.

The descending loop of Henle is only permeable to water. As the urine moves through the loop of Henle, it will become more concentrated as the water is reabsorbed back into the bloodstream. The ascending loop of Henle is permeable to sodium and during this portion of the loop, the urine will be come more diluted, as sodium ions are reabsorbed into the bloodstream.

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Correct Answer: B. Apoptosis

Apoptosis is programmed cell death or the process by which the cell self-destructs. It can be initiated under number of circumstances, such as when the cell has sustained significant damage to its DNA, and is carried out by a cellular cascade pathway. Apoptosis is beneficial to the organism because it can remove cells before the can become cancerous. Immortalization is a situation in which cells continue to divide past the number of times expected for that cell type. This is a common feature of cancer cells. Cellular senescence is a process of cellular aging in which the cell’s telomeres have shortened (through successive cell divisions) to the point that the cell no longer divides. Necrosis is cell death that is caused by some external insult, usually severe, and is not the result of a controlled, biological phenomenon.

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Correct Answer: C. Liverworts

A bryophyte lacks vascular tissues and seeds. These plants reproduce using spores and are dependent on water and air to carry the spores. A spruce is a type of cone-bearing plant, called a gymnosperm. A peach tree is an example of a fruit-bearing plant called an angiosperm. Ferns are vascular seedless plants and are in their own plant category. Bluegrass is a type of grass and grasses are considered to be an example of a monocot angiosperm. Liverworts and mosses are the most common examples of bryophytes.

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Correct Answer: E. Nematode – Invertebrate – Radial

For the animal kingdom, the simplest invertebrates are the sponges, which have no body symmetry. As animals become more advanced, invertebrates move from having no symmetry to having radial symmetry. The most advanced invertebrates have bilateral symmetry. Nematoda are round worms and are more advanced than the cnidarian like the jellyfish; therefore nematodes should have bilateral symmetry, not radial symmetry. Likewise, the chordate or vertebrate are all characterized as having bilateral symmetry. The only incorrect grouping is [E].

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Correct Answer: A. cilia.

The microtubules are part of the cytoskeleton and are comprised of a specialized protein called tubulin. Microtubules are integral in cell division and cell movement. Cilia are a type of cell movement and are made up of microtubules.

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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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