Question: Which of the following is not correct about the classical theory of chiasma formation and recombination?
Options:
A chiasma is formed when non-sister chromatids of homologous chromosomes become associated during synapsis
Chiasma formation is the reason for crossing over
Each chiasma does not lead to crossing over
Crossing over occurs during pachytene
• While the classical theory correctly states that:
– A. Chiasmata form when non-sister chromatids of homologous chromosomes associate during synapsis. This association involves a protein structure called the synaptonemal complex.
-B. Chiasma formation is the physical manifestation of crossing over. Chiasmata represent the points where genetic material has been exchanged between non-sister chromatids.
-C. Each chiasma does not necessarily lead to crossing over. While chiasmata often indicate crossing over, it's not guaranteed. Sometimes, chiasmata can resolve without actual exchange of genetic material.
🔴Related Terminologies::
-Chiasma: An X-shaped structure visible during meiosis where homologous chromosomes appear to exchange genetic material.
-Crossing over: The actual exchange of genetic material between non-sister chromatids of homologous chromosomes.
-Synapsis: The pairing of homologous chromosomes during meiosis.
– Synaptonemal complex: A protein structure connecting homologous chromosomes during meiosis, facilitating crossing over.
-Pachytene: A later stage of prophase I in meiosis where chromosomes condense and become visible.
-Zygotene: An earlier stage of prophase I in meiosis where homologous chromosomes first pair.