Which processes lead to the most genetic variation in sexually reproducing organisms? Select all that apply. Crossing over, independent orientation of chromosomes in meiosis, random fertilization, cytokinesis.
The Correct Answer and Explanation is:
Correct Answer:
✔ Crossing over
✔ Independent orientation of chromosomes in meiosis
✔ Random fertilization
Explanation:
Genetic variation is essential in sexually reproducing organisms because it contributes to diversity within a population. This diversity increases the chances of survival when environmental conditions change. Several key processes during sexual reproduction introduce this variation:
1. Crossing Over:
During prophase I of meiosis, homologous chromosomes pair up and exchange genetic material in a process known as crossing over or recombination. This results in chromosomes that carry a unique mix of genes from both parents. As segments of DNA are swapped between maternal and paternal chromosomes, entirely new combinations of alleles are created, significantly boosting genetic diversity in offspring.
2. Independent Orientation of Chromosomes in Meiosis:
In metaphase I of meiosis, homologous chromosome pairs align randomly at the cell’s equator. This means the maternal and paternal chromosomes are distributed into gametes independently of each other. The number of possible combinations depends on the number of chromosome pairs, calculated as 2ⁿ, where n is the haploid number. This random assortment generates a wide range of possible genetic combinations in gametes.
3. Random Fertilization:
Fertilization itself is random, meaning any sperm can fuse with any egg. Each gamete carries a different combination of genes due to crossing over and independent assortment. When fertilization occurs, the resulting zygote has a unique genetic identity that further increases variation within the population.
Cytokinesis, on the other hand, is the physical process of cell division that occurs at the end of mitosis or meiosis. It separates the cytoplasm and organelles into daughter cells but does not contribute directly to genetic variation. Its role is more mechanical than genetic.
Therefore, the processes that most contribute to genetic variation in sexually reproducing organisms are crossing over, independent orientation of chromosomes, and random fertilization.
