MCAT Biology : Embryogenesis

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

Example Question #1 : Reproductive System And Development

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

Possible Answers:

Two Y-chromosomes

A Y-chromosome

An X-chromosome

Two X-chromosomes

Both an X- and a Y-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 #2 : Biology

What is a totipotent cell?

Possible Answers:

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

Stem cells from the inner cell mass

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 #2 : Reproductive System And Development

What is the "common dogma"?

Possible Answers:

All cells come from other cells

All organisms are made of cells

None of the other answers

Cells lose genetic material over time, becoming less totipotent

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

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 #3 : Reproductive System And Development

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

Possible Answers:

produce urine

circulate blood

breathe

move

think

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.

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