Synapsis Definition
Synapsis is an event that occurs during meiosis in which homologous chromosomes pair with their counterparts and remain bound due to the exchange of genetic information. During meiosis, homologous chromosomes are paired and then separated to reduce the genetic content of the resulting gamete cells. Synapsis does not occur during mitosis, because homologous chromosomes do not pair with their counterparts. Synapsis starts when proteins connecting the various chromosomes to the nuclear membrane start to migrate. The proteins move around until their counterpart is found, and the synaptonemal complex is formed. The synaptonemal complex consists of protein and RNA, and hold the homologous chromosomes together.
Function of Synapsis
The synapsis of homologous chromosomes has a couple different functions in organisms. First, it holds the homologous chromosomes together through metaphase I of meiosis I, which allows them to be aligned on the metaphase plate and separated. This is a key task during meiosis, as this is how the genetic information in each gamete is reduced. Secondly, it allows homologous chromosomes to exchange information through crossing over. Crossing over occurs when similar portions of homologous chromosomes exchange position. This can redistribute how alleles interact with each other in the resulting organism. Synapsis ensures that alleles contained in these regions can be distributed independently of their parental source.
Related Biology Terms
- Meiosis – The process sexually-reproducing organisms use to create gametes with half the required genetic material to create a zygote.
- Crossing-over – Genetic recombination that occurs during meiosis, leading to novel forms.
- Recombination – The mixing of genetic material from different strands of DNA.
- Synaptonemal Complex – A protein and RNA structure that aids in forming the connections during synapsis of homologous chromosomes.
Quiz
1. If synapsis did not occur during meiosis, which of the following would be true?
A. Meiosis would be mitosis
B. No organism could exist
C. Gametes would still be created
2. During meiosis in an organisms, the process of synapsis malfunctions and does not release the homologs of a single pair of chromosomes. This extra copy gets transferred to the gamete, and eventually to the zygote. Why is this a potential problem?
A. Organisms cannot survive unless meiosis happens perfectly
B. The proteins produced by the chromosome may occur in excess
C. The extra chromosome will cause DNA damage
3. The synaptonemal complex holds homologous chromosomes together, all along their length. This is easy because homologous chromosomes are typically the same shape. In mammals, the sex chromosomes are specialized, and the female (X) chromosome is larger than the male (Y). What does this require during the synapsis of these homologous chromosomes?
A. The homologs do not undergo synapsis
B. The synaptonemal complex must only bond the homologs at the ends of the chromosomes
C. The chromosomes will undergo synapsis the same way most chromosomes do