Haploid and Diploid

• Haploid


  A cell has only one set of chromosomes
• Diploid


  A cell contains two sets of chromosomes
• Gametes


  • Have a haploid number of chromosomes
  • In humans, each gamete has one set of 23 chromosomes, so the haploid or n number is 23
• Fertilization


  1. Union of gametes creates a diploid cell called a zygote

  2. Zygote has two sets of chromosomes for a total of 46
• Homologous chromosomes

  Similar in shape and size, with the same types of genes in the same locations
• Somatic cells


  • Always diploid (2n), with two sets of 23 chromosomes for a total of 46 chromosomes
  • Other organisms have somatic cells with different diploid numbers of chromosomes
• Gametes


  • Always haploid, with half the diploid number of chromosomes
• Mitosis

  Somatic cells reproduce by mitosis, resulting in two genetically identical diploid daughter cells
• Meiosis


  Produces gametes, a diploid cell undergoes two cell divisions to produce four genetically different haploid gametes
• Diploid cells have two complete sets of chromosomes, one set from each parent
• Diploid cells have twice the number of chromosomes as haploid cells
• All somatic cells are diploid
• Diploid cells reproduce only by mitosis
• Gametes are never diploid, they are always haploid
• Haploid gametes form from diploid cells through meiosis, never through mitosis