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
Both an X- and a Y-chromosome
Two Y-chromosomes
A Y-chromosome
Two X-chromosomes
An X-chromosome
The necessary genotype for a female zygote isXX.
The mother will share thisXXgenotype (since she is also female) and will contribute one X-chromosome. The father, however, will be male and have the genotypeXY. 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 beXXand the offspring will be female.
Example Question #1 :Biology
What is a totipotent cell?
A cell that has the ability to form a complete organism through embryogenesis
年代tem 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
年代tem cells from adult tissues
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
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 :Biology
What is the "common dogma"?
All cells come from other cells
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
None of the other answers
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 :Embryogenesis
Differentiation of the endoderm in a developing human embryo will eventually give the human the ability to__________.
produce urine
think
breathe
move
circulate blood
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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