The term for a number of conditions that occur together and characterize a particular disease or condition (e.g., Down syndrome). | medical syndrome |
The general term for a chromosomal abnormality in which there is only one chromosome instead of the usual two homologous chromosomes for a particular pair. This is an example of aneuploidy. | monosomy |
The general term for a chromosomal abnormality in which there are 3 chromosomes instead of just 2 for a specific homologous pair. This is an example of aneuploidy. | trisomy |
The medical syndrome that is associated with an irregularity of autosome pair 21. In most cases, there is an extra chromosome (i.e., trisomy-21). More rarely (3-5%), there is a structural modification in this chromosome. The resulting syndrome involves mental retardation and abnormal physical appearance. | Down syndrome |
The medical syndrome that commonly causes people to have broad, short heads with small low-set ears, small concave saddle-shaped or flattened noses, relatively large ridged tongues that roll over a protruding lower lip, low muscle tone, and loose joints. Frequently, their eyes have an epicanthic fold. This medical syndrome also results in mental retardation. | Down syndrome |
The innermost membrane of the flexible sac enclosing a human or other mammal fetus. It is filled with amniotic fluid, which helps cushion the fetus and protect it from injury. | amnion or amniotic sac |
The membrane that develops around an embryo and contributes to the formation of the placenta in humans and other mammals. Later, as a fetus develops, this membrane fuses with the amnion. | chorion |
A fold of skin over the inner corner of each eyelid. This is characteristic of normal East Asians. It is also typical of people with Down syndrome from any population in the world. | epicanthic fold |
The period between conception and birth during which an unborn young is within its mother's uterus. Pregnancy is another word for it. | gestation |
An unborn child during the later stages of pregnancy. In humans, it develops from an embryo usually after the 8th week of gestation. Unlike embryos, they have clearly recognizable physical characteristics of the species and gender. | fetus |
An organ that develops from the chorion of an embryo during gestation and grows into the wall of the uterus. It is connected to an unborn child by the umbilical cord. This organ provides oxygen, nutrients, and antibodies for a fetus. Following birth, this organ and the umbilical cord are naturally expelled from the uterus as the "afterbirth." | placenta |