What is a Bivalent?
A bivalent is the association of two homologous chromosomes from each parent. It consists of two chromosomes and four chromatids. The two chromosomes come in association as a result of crossing over. They are joined together at a point called chiasmata.
The bivalent is also referred to as a tetrad. It is formed during the prophase I of meiosis. The formation of such tetrads helps in the segregation of chromosomes in the later stages of meiosis.
What is a Synaptonemal Complex?
The synaptonemal complex is a proteinaceous structure that is formed between homologous chromosomes. It is a tripartite structure that consists of a central element and two parallel lateral regions.
The complex starts to assemble around the chromosomes at the starting of the leptotene stage; synapsis takes place at the zygotene stage, and by the end of the pachytene stage, the complex starts to disappear. It is lined along the length of the homologous chromosomes.
The three components of the tripartite complex are SYCP-1, SYCP-2 and SYCP-3. The formation of the synaptonemal complex helps in synapsis and recombination of the homologous chromosomes.
Bivalent vs. Synaptonemal Complex
|
Bivalent |
Synaptonemal Complex |
| Definition | |
| An association between two homologous chromosomes from two different parents is referred to as a bivalent. | A tripartite proteinaceous structure found around the homologous chromosomes is referred to as the synaptonemal complex. |
| Composition | |
| It is composed of two homologous chromosomes, i.e., four chromatids. | It is composed of three proteins: SYCP-1, SYCP-2 and SYCP-3. |
| Importance | |
| It helps in the recombination between the homologous chromosomes. | It joins the homologous chromosomes along their lengths. |
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Also Read:
- What Happens During Synapsis In Meiosis?
- What Happens To The Bivalent Chromosomes In Metaphase I?
- How Do You Identify Homologous Chromosomes?
Frequently Asked Questions
What is the difference between synaptonemal complex and chiasmata?
Synaptonemal complex is a structure formed around homologous chromosomes that supports the exchange of genetic material between them. On the other hand, chiasmata is the point of crossing over between homologous chromosomes.
What is the difference between chiasmata and chiasma?
Chiasma is a singular word, whereas chiasmata is a plural word.
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