An embryo develops rudiments of all organs by week ________ of prenatal development.
A) 8
B) 4
C) 6
D) 3
A) 8
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Scaffolding proteins are _____
A) ladderlike proteins that allow receptor-ligand complexes to climb through cells from one position to another B) microtubular protein arrays that allow lipid-soluble hormones to get from the cell membrane to the nuclear pores C) large molecules to which several relay proteins attach to facilitate cascade effects D) relay proteins that orient receptors and their ligands in appropriate directions to facilitate their complexing E) proteins that can reach into the nucleus of a cell to affect transcription
The recessive allele that causes phenylketonuria (PKU) is harmful, except when an infant's diet has appropriate levels of the amino acid phenylalanine. What maintains the presence of this harmful allele in a population's gene pool?
A) heterozygote advantage B) stabilizing selection C) diploidy D) balancing selection
Trisomy 21 (Down syndrome) is the only example of an autosomal trisomy in which the fetus develops to term and is born alive
A. true B. false
Sweat is released by exocrine glands on the skin surface as a means to lower body temperature
Indicate whether the statement is true or false