acrosomal reaction

release of digestive enzymes by sperm that enables them to burrow through the corona radiata and penetrate the zona pellucida of an oocyte prior to fertilization

acrosome

cap-like vesicle located at the anterior-most region of a sperm that is rich with lysosomal enzymes capable of digesting the protective layers surrounding the oocyte

afterbirth

third stage of childbirth in which the placenta and associated fetal membranes are expelled

allantois

finger-like outpocketing of yolk sac forms the primitive excretory duct of the embryo; precursor to the urinary bladder

allele

alternative forms of a gene that occupy a specific locus on a specific gene

amnion

transparent membranous sac that encloses the developing fetus and fills with amniotic fluid

amniotic cavity

cavity that opens up between the inner cell mass and the trophoblast; develops into amnion

autosomal chromosome

in humans, the 22 pairs of chromosomes that are not the sex chromosomes (XX or XY)

autosomal dominant

pattern of dominant inheritance that corresponds to a gene on one of the 22 autosomal chromosomes

autosomal recessive

pattern of recessive inheritance that corresponds to a gene on one of the 22 autosomal chromosomes