DAT Question of the Day

Correct Answer: B. They are responsible for the supercoiling of DNA.

Histones are not responsible for methylating DNA(A) or helping topoisomerase enzymes bind. Histones interact with DNA through ELECTROSTATIC interactions, and an octet of histones plus a length of DNA forms a NUCLEOSOME and causes the DNA to form its tertiary structure and become supercoiled.

Subscribe below to get the DAT Question of the Day delivered straight to your inbox every morning.

Correct Answer: B. Blood

The three primary germ layers of the embryo include: the ectoderm, endoderm, and mesoderm. The endoderm differentiates to form the gastrointestinal tract, the lungs, the pharynx and parts of the urinary system. The ectoderm is the outer layer of the three germ layers and results in the formation of the epidermis and related structures like hair, nails, and external sense organs. The ectoderm also forms the spinal cord and the brain. The mesoderm is the middle layer of the three germ layers and eventually develops into connective tissues (including bone), cartilage, muscle, and the blood vessels. Blood is considered a type of connective tissue, thus the correct answer is [B].

Subscribe below to receive the DAT Question of the Day delivered straight to your inbox every morning.

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.

Subscribe below to receive the DAT Question of the Day delivered straight to your inbox every morning.

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.

Subscribe below to receive the DAT Question of the Day delivered straight to your inbox every morning.

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.

Subscribe below to receive the DAT Question of the Day delivered straight to your inbox every morning.

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.

Subscribe below to receive the DAT Question of the Day delivered straight to your inbox every morning.

Correct Answer: B. perforin

Cytotoxic T-cells are able to rid the body of infections that have spread to cells. To do this, cytotoxic T-cells release perforin, which disintegrates the cell membrane, causing the infected cell to lyse and then be engulfed by macrophages. Antibodies are released from B-cells that then aggregate to an antigen, tagging it to be eaten by macrophages. Actin and tubulin are proteins present in the cytoskeleton and histamine is a chemical released during an allergic reaction or to initiate an inflammatory response.

Subscribe below to get the DAT Question of the Day delivered straight to your inbox every morning.

Correct Answer: C. pH levels

The brain triggers the diaphragm to contract and lower to spur inhalation when the pH levels begin to drop. In the presence of high amounts of CO2, the blood’s pH begins to become acidic, which is detected by chemoreceptors. This will initiate inhalation, where CO2 will be expelled and oxygen will be absorbed into the capillaries in the alveoli, thereby restoring blood’s neutral pH.

Subscribe below to get the DAT Question of the Day delivered straight to your inbox every morning.