BiologyCambridge IGCSE


Inheritance is the transmission of genetic information from generation to generation. Genetic information is stored in the form of DNA within the cell nucleus. Each organism has pairs of chromosomes, one inherited from the mother and one from the father. The chromosomes carry genes, which are segments of DNA that code....


  • Inheritance is the transmission of genetic information from generation to generation

Chromosomes, Genes and Proteins

  • A chromosome is a thread-like structure of DNA, carrying genetic information in the form of genes
  • A gene is a length of DNA that codes for a protein
  • An allele is a version of a gene
  • A haploid nucleus is a nucleus containing a single set of unpaired chromosomes, e.g., in gametes (sex cells have n number of chromosomes)
  • A diploid nucleus is a nucleus containing two sets of chromosomes, e.g., in body cells. In a diploid cell, there is a pair of each type of chromosome. In a human diploid cell, there are 23 such pairs (body cells have 2n number of chromosomes)


  • Mitosis is the nuclear division giving rise to genetically identical cells

This type of cell division is used for:

  • Growth
  • Repair of damaged tissues
  • Replacement of cells
  • Asexual reproduction (such as binary fission or budding)

Before mitosis, the exact duplication of chromosomes occur. During mitosis, the copies of chromosomes separate, maintaining the chromosome number. This happens in all the parts of the body.

The fusion of the male and female gamete is known as fertilization and it forms a zygote. This will then divide (by mitosis) to form a ball of identical cells called the embryo. The embryo of an organism consists of stem cells. These unspecialized cells can divide by mitosis to produce daughter cells that will specialize to form different parts of the organism to carry out specific functions. This process is known as cell specialization.


  • Meiosis is the reduction division in which the chromosome number is halved from diploid to haploid, resulting in genetically different cells

In meiosis, the chromosomes are halved, therefore it is involved in the production of gametes. It will take place in the sex organs of an organism. This provides genetic variation as many combinations of maternal and paternal chromosomes form genetically different sex cells, and therefore an offspring will be unique as 2 of the genetically different sex cells fuse to form the zygote.

Mitosis Meiosis
2 cells produced 4 cells produced
Diploid daughter cells Haploid daughter cells
Daughter cells are genetically identical to each other and the parent cell Daughter cells are genetically different from each other and the parent cell
1 cell division occurs 2 cell divisions occur

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