Molecular Genetics

Chromosome Structure: The DNA molecule itself has two strands twisted into a double helix. At regular intervals, the DNA molecule (blue) wraps around a core of histone proteins (purple). The DNA and proteins associated with it twist tightly into a fiber. The fiber coils and then coils again to form a hollow cylinder. At its most condensed, a duplicated chromosome has an X shape.

The four nucleotides that make up DNA. Each kind has three phosphate groups, a deoxyribose sugar (orange), and a nitrogen-containing base (blue) after which it is named.

Rosalind Franklin and her x-ray diffraction image of DNA. This image was the final link in a long chain of clues that led to the discovery of DNA's structure.

DNA Structure

DNA replication, in which a doublestranded molecule of DNA is copied in entirety. Two double-stranded DNA molecules form; one strand of each is parental (old), and the other is new, so DNA replication is said to be semiconservative.

Two types of DNA damage that can lead to mutations.

Somatic cell nuclear transfer, using cattle cells. This series of micrographs was taken by scientists at Cyagra, a company that specializes in cloning livestock.

Visuals