MCAT Biology : Embryogenesis
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Example Question #1 : Biology
To form a female zygote, the sperm cell must contribute which chromosome(s)?
An X-chromosome
Two X-chromosomes
Both an X- and a Y-chromosome
A Y-chromosome
Two Y-chromosomes
An X-chromosome
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 : Embryogenesis
What is a totipotent cell?
A cell that has the ability to form a complete organism through embryogenesis
A cell that has the ability to differentiate into any type of tissue if exposed to the appropriate chemical signals
Stem cells from adult tissues
A cell that has the ability to differentiate into a limited number of tissue types if exposed to the appropriate chemical signals
Stem cells from the inner cell mass
A cell that has the ability to form a complete organism through embryogenesis
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"?
None of the other answers
Cells lose genetic material over time, becoming less totipotent
All cells come from other cells
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
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
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 __________.
think
produce urine
move
circulate blood
breathe
breathe
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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