MCAT Biology : Systems Biology and Tissue Types

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

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Example Question #1 : Biology

To form a female zygote, the sperm cell must contribute which chromosome(s)?

Possible Answers:

A Y-chromosome

Two Y-chromosomes

Two X-chromosomes

Both an X- and a Y-chromosome

An X-chromosome

Correct answer:

An X-chromosome

Explanation:

The necessary genotype for a female zygote is XX.

The mother will share this XX genotype (since she is also female) and will contribute one X-chromosome. The father, however, will be male and have the genotype XY. This means he has a 50% chance of passing on an X-chromosome and a 50% chance of passing on a Y-chromosome. If the zygote inherits a Y-chromosome from the father's sperm, then the offspring will be male. If the zygote inherits an X-chromosome from the father's sperm, then the resulting genotype will be XX and the offspring will be female.

Example Question #1 : Reproductive System And Development

What is a totipotent cell?

Possible Answers:

Stem cells from the inner cell mass

A cell that has the ability to differentiate into a limited number of tissue types if exposed to the appropriate chemical signals

A cell that has the ability to differentiate into any type of tissue if exposed to the appropriate chemical signals

A cell that has the ability to form a complete organism through embryogenesis

Stem cells from adult tissues

Correct answer:

A cell that has the ability to form a complete organism through embryogenesis

Explanation:

Totipotent cells have the ability to propogate and differentiate into any cell types, including the trophoblast. They are different from stem cells, which could be considered multipotent (able to differentiate into multiple tissue types) or pleuripotent (able to differentiate into any major tissue type, but cannot create trophoblast). The only truly totipotent cells are the first two blastomeres.

Example Question #1 : Systems Biology And Tissue Types

What is the "common dogma"?

Possible Answers:

Cells lose genetic material over time, becoming less totipotent

All cells come from other cells

None of the other answers

Most cells in the body contain a complete genome, despite the fact that most of the genes in the genome are not necessary for each cell's specific function

All organisms are made of cells

Correct answer:

Most cells in the body contain a complete genome, despite the fact that most of the genes in the genome are not necessary for each cell's specific function

Explanation:

Most cells contain a complete genome, but not all genes are activated in each cell. Activation of particular genes produces appropriate protein function.

Example Question #1 : Reproductive System And Development

Differentiation of the endoderm in a developing human embryo will eventually give the human the ability to __________.

Possible Answers:

breathe

think

move

produce urine

circulate blood

Correct answer:

breathe

Explanation:

The endoderm develops into a number of internal organs, including the lung, which are vital for breathing.

The kidneys (urine production), muscles (movement), and blood vessels (blood circulation) develop from the mesoderm. The brain (thought) develops from the ectoderm.

Example Question #1 : Biology

A new medication has been created that is very effective at treating brain tumors; however, the medication has a short half-life once inside the body. If the medication travels through the blood stream, which method of administration would give the medication the most time to affect a tumor in the brain? (Assume an equal dosage of the medicine is used for each potential method.)

Possible Answers:

Inhalation

Sublingual

Subcutaneous Injection

Intravenous Injection (Jugular Vein)

Correct answer:

Inhalation

Explanation:

This question is targeting your knowledge of the circulatory system. Since the medication has a short half-life, it is necessary that it be carried by the patient's blood stream to the tumor as quickly as possible. Blood travels through the right side of the heart, to the lungs, through the left side of the heart, then to the body. Therefore, inhalation of a chemical would require the least amount of traveling (Lungs, Left Atrium, Left Ventricle, Body). Each other method of administration, including IV, would require more time to travel to the brain. For example, for the IV answer choice, the pathway would be Vein, Right Atrium, Right Ventricle, Lungs, Left Atrium, Left Ventricle, Body.

Example Question #1 : Reproductive System

Follicle-stimulating hormone (FSH) stimulates the growth of a follicle in the ovary, a process that occurs __________.

Possible Answers:

between fertilization and birth

only before the female is born

between puberty and menopause

between birth and puberty

Correct answer:

between puberty and menopause

Explanation:

At puberty, the oocytes arrested at birth in meiosis I resume growth. This most often happens once a month, if fertilization has not occurred, and continues from puberty until menopause. The oocytes arrested at birth complete meiosis I, and are then arrested in meiosis II until fertilization occurs. During ovulation, the follicle ruptures and develops into the corpus luteum. Without fertilization, the endometrium is shed and the cycle continues. Once menopause is reached, this cycle ceases and most often women are no longer fertile.

Example Question #1 : Systems Biology And Tissue Types

The hormones FSH and LH are involed in oogenesis in women. When LH surges in the ovarian cycle, what event will result?

Possible Answers:

Ovulation

Corpus luteum degradation

Menstruation

None of the above

Endometrium proliferation

Correct answer:

Ovulation

Explanation:

Follicles are stimulated to grow when FSH level rises. The follicles produce estrogen that exerts a positive feedback on LH, whose levele begin to rise. When LH levels peak on the 14th day of the cycle, the follicle ruptures, releasing the egg from the ovary and leaving the corpus luteum behind in the ovary. After ovulation, the corpus luteum secretes both estrogen and progesterone to inhibit GnRH. When GnRH is inhibited, FSH and LH will also be inhibited. 

Example Question #2 : Reproductive System And Development

An environmental toxin has been found to directly disrupt normal gamete production in women. What tissue or organ is the toxin likely localizing to?

Possible Answers:

Ovaries

None of these

Oviduct

Endometrium

Uterus

Correct answer:

Ovaries

Explanation:

The most likely localization of the toxin would be to the ovaries, since this is where gamete production begins for females. For males, gametes are produced in the testes. The incorrect answers are all parts of the female reproductive system. The oviduct is where fertilization takes place. The endometrium (the lining of the uterus) is where the embryo will eventually implant.

Example Question #1 : Reproductive System

Which of the following describes the function of follicle-stimulating hormone in females?

Possible Answers:

Promote growth of immature follicles in ovaries

Increase basal metabolic rate

Promote milk production

Stimulate estrogen secretion from ovaries

Correct answer:

Promote growth of immature follicles in ovaries

Explanation:

Follicle-stimulating hormone stimulates the growth of granulosa cells surrounding the primary oocyte within the ovary, which further promotes maturity of the immature follicle. Prolactin is the hormone that promotes milk production from mammary glands during pregnancy. In females, luteinizing hormone (LH) supports theca cells in the ovaries, which subsequently give rise to precursors to estrogen production. Thyroid hormones regulate metabolism by increasing basal metabolic rate. 

Example Question #1 : Female Reproductive Physiology

Progesterone is primarily secreted by which of the following structures?

Possible Answers:

Primary follicle

Corpus luteum

Ovum

Secondary follicle

Spermatozoon

Correct answer:

Corpus luteum

Explanation:

The corpus luteum is the remnant structure of the secondary follicle after the egg is released during ovulation. It secretes progesterone following this process. The other structures do not release appreciable amounts of progesterone; the primary follicle differentiates into the secondary follicle, which in turn releases the ovum, or the egg. The spermatozoon is involved with the fertilization of the egg, and does not release any progesterone. 

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