Tetrad (meiosis)

A group of four chromatids formed during meiosis

Tetrad in the context of meiosis refers to a group of four closely associated chromatids of a homologous pair of chromosomes. This structure is crucial for the process of genetic recombination and segregation of chromosomes during meiosis.

Formation of Tetrads

During the early stages of meiosis, specifically in prophase I, homologous chromosomes pair up in a process known as synapsis. Each chromosome consists of two sister chromatids, and when homologous chromosomes pair, they form a structure known as a tetrad. This tetrad consists of four chromatids: two from each homologous chromosome.

Riccia sorocarpa spores

Function of Tetrads

The formation of tetrads is essential for the process of crossing over, where genetic material is exchanged between homologous chromosomes. This exchange of genetic material increases genetic diversity in the resulting gametes. The points where crossing over occurs are known as chiasmata, and they hold the homologous chromosomes together until they are separated during anaphase I of meiosis.

Separation of Tetrads

As meiosis progresses, the tetrads align at the metaphase plate during metaphase I. The homologous chromosomes are then pulled apart to opposite poles of the cell during anaphase I. This separation reduces the chromosome number by half, which is a key feature of meiosis, leading to the production of haploid cells.

Tetrads in Different Organisms

Tetrads are observed in various organisms during meiosis, including plants, fungi, and animals. In some fungi, such as yeast, the products of meiosis remain together in a structure called an ascus, which can be observed as a tetrad of spores.

Yeast tetrad

Significance of Tetrads

The formation and proper segregation of tetrads are crucial for ensuring genetic diversity and stability across generations. Errors in tetrad formation or separation can lead to nondisjunction, resulting in gametes with abnormal numbers of chromosomes, which can cause genetic disorders.

Related pages

• Meiosis
• Chromosome
• Genetic recombination
• Crossing over
• Nondisjunction