DAT Question of the Day

Correct Answer: D. Obligate Anaerobes

The term obligate means that this is a required condition that has to be met to ensure the viability of the organism. An obligate aerobe has to have oxygen present to be able to survive, like humans. Likewise, an organism that cannot live in the presence of oxygen would be an obligate anaerobe. Facultative anaerobes can survive in the presence of oxygen, but prefer aerobic environments. Permissive anaerobe is a term that does not exist in biology. Aerotolerant organisms do not require oxygen, but they are not poisoned by it either.

1. Obligate aerobes need oxygen to survive because they rely on aerobic respiration.
2. Obligate anaerobes cannot survive with oxygen.
3. Facultative anaerobes grow with or without oxygen, but prefer oxygen environments because they can generate more ATP through aerobic respiration.
4. Microaerophiles need oxygen to survive, but they are poisoned by high concentrations of oxygen.
5. Aerotolerant organisms do not require oxygen, but they are not poisoned by it either.
Source from Wikipedia

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Correct Answer: B. The gap between the myelin sheath segments

The correct answer is B. The gap between the axon terminal and dendrite of the next neuron is called the synaptic cleft. The lipid-based coating that covers the neurons is the myelin sheath, and this sheath covers segments along the axon called internodes and the gaps between these internodes are called the Nodes of Ranvier.

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Correct Answer: D. enteropeptidase and trypsin

After releasing trypsinogen from the pancreas, enteropeptidase cleaves the inactive protein at specific sites. As a consequence of this action trypsin is generated. This enzyme has ability to generate trypsinogen on its own and to release an active enzyme.

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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.

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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].

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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: 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. 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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