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Male infertility—the inability of sperm cells to fertilize an egg cell—has several causes. if, during fetal development, the testes do…

Wrist and Bones of Hand PhalangesMetacarpalsTrapeziumScaphoidLunateTriquetrumPisiformHamateCapitateTrapezoid Radiograph: Wrist PisiformHamateCapitateTrapezoidTrapeziumScaphoidRadiusLunateTriquetrumUlna Radiograph in anterioposterior beam projection

People have studied cells for centuries. We know exactly what cells are made of, from their DNA and RNA to…

All living things use DNA or RNA to store genetic information. But eukaryotes are different from bacteria and archaea in…

DNA fingerprinting (also known as DNA profiling or DNA typing) refers to any technique for identifying individuals based on the…

Headaches have many triggers. Muscle tension, nighttime teeth-grinding, stress and anxiety, bright lights, and some food ingredients are just a…

Humans have about 20,000 protein-coding genes. Scientists have found that about 3800 of those genes are continually expressed in all…

Metabolism describes all the chemical reactions in a cell. Because our cells always lose energy as heat, they require constant…

No one knows exactly how growth rates will change in the future, so it is impossible to predict when or…

Two invertebrates, a roundworm and an arthropod, share the spotlight in this box. Both have the characteristics common to all…