Nucleus

The nucleus is the organelle that holds the cell’s genetic material and controls the activities of the cell ¹. It is present in plant and animal cells, and absent from bacterial cells, whose circular DNA lies free in the cytoplasm.

Genetic Material

• Chromosomes are made of DNA, which contains genetic information in the form of genes.
• A gene is a length of DNA that codes for a protein, and DNA controls cell function by controlling the production of proteins, including enzymes and receptors ¹.
• The sequence of bases in a gene determines the sequence of amino acids used to make a specific protein.

Nucleus in Reproduction

Nuclei are the structures that carry genetic information from generation to generation: the nuclei of gametes are haploid, and fertilisation — the fusion of the nuclei of two gametes — forms a diploid zygote ¹. Each offspring therefore inherits genetic material from two parents.

Related

• Nuclear Envelope - Double membrane enclosing the nucleus.
• DNA - Molecule carrying the genetic information.
• Ribosome - Builds proteins from the instructions the DNA carries.
• Cell - Structural unit containing the nucleus.
• Reproduction - Gamete nuclei fuse at fertilisation.
• Biology - Cambridge IGCSE life-science area.