Final answer:
In summary, each chromatid consists of a single double-stranded DNA molecule and carries the same set of genes. Chromosomes, each having two sister chromatids, contain DNA and proteins. Human somatic cells are normally diploid with 46 chromosomes, but have 92 chromatids following DNA replication.
Step-by-step explanation:
The Structure of Chromosomes
The human body is made up of billions of cells that divide every day. After DNA replication in the synthesis phase (S phase) of interphase, each cell contains two copies of each chromosome. These copies are called sister chromatids, which are held together by the centromere.
Each chromatid is composed of a single molecule of double-stranded DNA and contains an identical set of genes, which determine specific characteristics of an organism. Chromosomes are made of both DNA and proteins, including histones, which form a structure known as chromatin. This chromatin further condenses during cell division, when chromosomes become highly coiled.
Human somatic cells normally contain 46 chromosomes, and after DNA replication, 92 chromatids are present. Eukaryotic cells, like human cells, have a characteristic number of chromosomes. In humans, each somatic cell is diploid (2n), containing two sets of chromosomes, while gametes (sperm and eggs) are haploid (n), containing one set.