DNA and Chromosomes

Inside the nucleus of a cell, there are thread-like structures called chromosomes. Each chromosome is made out of a long, coiled strand of DNA (genetic material), which means that each chromosome contains many genes.

Normally, there are 46 chromosomes inside the nucleus of each human body cell. These chromosomes are usually found in pairs.

Diagram of a chromosome and DNA structure showing the somatic cell, nucleus, and chromosome

A diploid cell contains two complete sets of chromosomes within its nucleus, one inherited from each parent. In humans, all body cells are diploid cells. Human diploid cells contain 23 pairs of chromosomes (46 in total). The diploid number is often represented as 2n, where n represents the number of chromosomes. For humans, 2n = 46.

The term haploid means half. It describes a cell that holds a single set of chromosomes. The symbol n is often used to show the haploid number. For humans, n = 23. Human sex cells (egg and sperm cells) contain a single set of chromosomes, so they are haploid cells.

  • Sex cells are also called gametes

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