The nucleus of a cell contains chromosomes, which carry genetic information in a long molecule called DNA. Genes are regions of DNA that carry the code to control a particular cell activity or the production of a particular protein.
Asexual reproduction produces genetically identical individuals, but sexual reproduction produces unique individuals.
The nucleus of a cell contains chromosomeschromosomes: Rod shaped bodies found in the nucleus of cells that contain genetic information (DNA). that carry genetic information. Most body cells have the same number of chromosomes, but this varies between species. Human body cells, for example, each have 23 matching pairs of chromosomes.
Chromosomes are made from long, coiled molecules of DNA [DNA: The material inside the nucleus of cells, carrying genetic information. DNA stands for Deoxyribonucleic Acid. ]. A gene gene: The basic unit of genetic material inherited from our parents. A gene is a section of DNA which controls part of a cell's chemistry - particularly protein production. is a shorter region of DNA that carries the genetic code for a particular characteristic or cell activity.
DNA molecules contain chemicals called bases. Note that these are not the bases you come across in chemistry - which neutralise acids. DNA contains four different bases. Each gene has a different sequence of bases, coding for different products.
The four bases in DNA are labelled A, T, C and G.
Only some of the genes are used in any individual cell, with the rest being switched off. Genes code for the production for proteins. Some of these are enzymes which control how the cell functions.
This slideshow demonstrates how a protein is produced using the genetic code.How a protein is produced using the genetic code
Genes contain bases in groups of three
Each triplet of bases has the instructions for making a particular amino acid
The amino acids join together in the order given by the base triplets
Asexual reproduction only needs one parent. All the offspring are genetically identical to each other, and their parent. They are clones.
Sexual reproduction needs two parents. Each parent produces sex cells, called gametes:
Each gamete contains half the number of chromosomes that a body cell has. At fertilisation, a male and female gamete fuse or join together. The new cell contains the full number of chromosomes.
Half of its genes have come from the father, and half have come from the mother. The genetic material from both parents has combined to form a unique individual.
Genetic material is randomly mixed during fertilisation. Any two gametes can randomly meet and fuse, producing a unique combination of genetic information in the offspring.