Sex Limited Trait
A phenotype expressed in only one sex, although it may be due to a sex linked or autosomal gene.

Sex Linked
Traits or diseases associated with the X or Y chromosome; generally seen in males.

Sex Linked Inheritance
A special inheritance pattern for genes located on the X chromosome; the trait in question may be observed only in heterogametic individuals, and much less frequently in homogametic individuals.

SGA
Small for gestational age the child is born smaller than expected for their age (usually describing smaller than the third percentile) for the gestational age.

Shine Delgarno sequence
A nucleotide sequence (AGGAGG) that is present in the 5 untranslated region of prokaryotic mRNAs. This sequence serves as a binding site for ribosomes.

Short Stature
Smaller in height than expected for chronological age.

Shotgun method
Sequencing in height than expected for chronological age.

Sickle Cell Disease
An autosomal recessive genetic condition where the hemoglobin protein is mutated giving red blood cells a sickle shape that can block circulation. This condition caused lifelong anemia and other chronic problems and is found mostly in individuals of African or Mediterranean origin.

Sickle Cell Anemia
A genetic disease in humans, caused by a single amino acid change in the beta chain of globin. Affected erythrocytes have a sickle shape instead of the typical biconcave disk shape. The trait is autosomal recessive, and is often fatal in the homozygous condition.
2. A disease in which poorly formed red blood cells cannot bind correctly to oxygen, resulting in low iron, blood clotting, and joint pain.