Respuesta :
Meiosis occurs in a series of different phases and creates genetically unique reproductive cells. The process which helps make meiotic cells genetically different and occurs during prophase I, but not during prophase II, is crossing over (C). Crossing over is the exchange of genetic material between two homogenous chromosomes. It is one of the final phases of prophase I. This process is called synapsis. It occurs when the matching regions on the matching chromosomes break and then reconnect to the other chromosome
The process of crossing over takes place in prophase I and creates genetic diversity in the meiotic cells whereas prophase II is devoid of any such process.
Further Explanation:
The type of cell division which helps in gamete production is meiosis. It starts with prophase I in which the cell contains duplicated chromosomes. The chromosome duplication occurs during interphase which is followed by prophase I.
In the prophase I, the homologous chromosomes align with each other resulting in a tetrad formation. As the chromosomes line up, the genetic material is interchanged between the chromosomes. This is called crossing over which allows the formation of genetically unique daughter cells during the process of meiosis. Crossing over enhances the genetic diversity among the chromosomes as the hybrid chromosomes formed after crossing over have unique patterns. During crossing over, synapse occurs which is the pairing of two homologous chromosomes. A crisscross structure is formed between the two non-sister chromatids. It is the point of contact where the genetic exchange takes place to form new combinations of alleles.
As the crossing over completes, the homolog pairs move towards the center of the cell or alignment and this stage is called metaphase I. The pairs separate during anaphase I and migrate to their respective poles keeping the sister chromatids together. By the end of the telophase I, two new haploid cells are formed.
As the meiosis II proceeds with prophase II, no chromosome duplication takes place. The chromosome condenses followed by the breakdown of the nuclear envelope. The spindle formation occurs and the microtubules bind to the chromosomes. The chromosomes containing the sister chromatids line up during metaphase II at the center and gets separated in the anaphase II. Finally, at the telophase II daughter cells are formed which are four in numbers with each containing different sets of chromosomes as a result of random segregation or crossing over.
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Answer Details:
Grade: High School
Subject: Biology
Chapter: Meiosis
Keywords:
Meiosis, prophase, metaphase, anaphase, telophase, crossing over, chiasmata, synapse, sister chromatids, non-sister chromatids, homologous chromosomes, chromosomes, alleles, genetic diversity, genetic variation, chromosome duplication.
