Asexual reproduction

Asexual reproduction is the production of offspring from one parent, without a genetic contribution from a second parent. The offspring receive genetic information from that one parent, so they are genetically identical to the parent and to one another.

Identifying asexual reproduction

In a diagram, image or written description, look for evidence that one parent produces offspring without a genetic contribution from another parent. The number of offspring does not determine whether reproduction is asexual: the key evidence is where their genetic information comes from. An image showing only one parent may not, by itself, establish whether a second parent contributed genetic information.

Sexual reproduction

Sexual reproduction produces a new organism when two sex cells, called gametes, join. Each gamete carries a nucleus containing genetic material from a parent.

The nuclei of the two gametes fuse during fertilisation. This produces a zygote, the first cell of the new organism. The zygote contains genetic material from both parents and develops into the offspring.

Genetic variation in sexual reproduction

Offspring produced by sexual reproduction receive genetic material from two parents. Different offspring usually receive different combinations of that material, so they are genetically different from each other. These genetic differences are called genetic variation.

Fertilisation is the specific step in which the gamete nuclei fuse. Sexual reproduction is the wider process: it includes fertilisation and the formation of a zygote, and it leads to genetic variation among offspring.

Mitosis

Mitosis produces two new cells from one parent cell. The two new cells, called daughter cells, have the same number of chromosomes as the parent cell and normally have the same genetic information as the parent cell and each other.

Before the cell divides, it copies its DNA. During mitosis, the chromosome copies are separated into two nuclei, so each nucleus receives the same genetic information. The cell then divides to form two daughter cells, each with one of the nuclei.

Mitosis in asexual reproduction

Asexual reproduction produces offspring from one parent. It uses mitosis, so the offspring have the same genetic information as the parent: they are genetically identical clones. There is no fusion of gametes and no mixing of genetic information from two parents.

Gametes

Gametes are reproductive sex cells. Sperm cells and egg cells are examples of gametes.

Most body cells contain two sets of chromosomes. A gamete contains only one set, so it is described as haploid. Chromosomes carry genes, and a gamete normally carries one allele of each gene present on its chromosomes. An allele is a version of a gene.

At fertilisation, two gametes fuse and their chromosome sets combine. The resulting cell therefore has two sets of chromosomes, with one set from each parent. This means the offspring receives genetic information from both parents.