How does fertilisation lead to genetic variation

Meiosis 4. Inheritance 5. Genetic Modification 4: Ecology 1. Energy Flow 3. Carbon Cycling 4. Climate Change 5: Evolution 1. Evolution Evidence 2. Natural Selection 3. Classification 4. Cladistics 6: Human Physiology 1. Digestion 2. The Blood System 3. Disease Defences 4. Gas Exchange 5. Homeostasis Higher Level 7: Nucleic Acids 1. DNA Structure 2. Transcription 3. Translation 8: Metabolism 1. Metabolism 2. Search for:. Genetic Variation in Meiosis Learning Outcomes Understand how meiosis contributes to genetic diversity.

Try It. Did you have an idea for improving this content? Reece, J. Urry, M. Cain, S. Wasserman, P. Although we are all unique, there are often obvious similarities within families. Maybe you have the same nose as your brother or red hair like your mother? Family similarities occur because we inherit traits from our parents in the form of the genes that contribute to the traits. This passing of genes from one generation to the next is called heredity. Simple organisms pass on genes by duplicating their genetic information and then splitting to form an identical organism.

More complex organisms, including humans, produce specialised sex cells gametes that carry half of the genetic information, then combine these to form new organisms. The process that produces gametes is called meiosis. During meiosis in humans, 1 diploid cell with 46 chromosomes or 23 pairs undergoes 2 cycles of cell division but only 1 round of DNA replication.

The result is 4 haploid daughter cells known as gametes or egg and sperm cells each with 23 chromosomes — 1 from each pair in the diploid cell. At conception, an egg cell and a sperm cell combine to form a zygote 46 chromosomes or 23 pairs. This is the 1st cell of a new individual.

The halving of the number of chromosomes in gametes ensures that zygotes have the same number of chromosomes from one generation to the next. This is critical for stable sexual reproduction through successive generations. Replication of DNA in preparation for meiosis. After replication, each chromosome becomes a structure comprising 2 identical chromatids.

The chromosomes condense into visible X shaped structures that can be easily seen under a microscope, and homologous chromosomes pair up.