Sexual reproduction increases genetic variability through:
a) crossing over in prophase I of meiosis
b) independent assortment in meiosis
c) fertilization
d) binary fission
e) a, b, and c
The correct answer and explanation is:
The correct answer is e) a, b, and c.
Sexual reproduction increases genetic variability through several mechanisms that occur during meiosis and fertilization.
- Crossing over in prophase I of meiosis: During prophase I of meiosis, homologous chromosomes pair up and exchange segments in a process called crossing over. This exchange of genetic material results in new combinations of alleles on each chromosome, increasing genetic diversity. Since crossing over happens between homologous chromosomes, it ensures that offspring inherit a unique combination of genes from both parents.
- Independent assortment in meiosis: During metaphase I of meiosis, homologous chromosome pairs align randomly along the cell’s equator. This random arrangement of chromosomes is called independent assortment. It means that each gamete (egg or sperm) will have a different combination of maternal and paternal chromosomes, further increasing genetic variation. The number of possible combinations of chromosomes is 2^n, where n is the number of chromosome pairs. For humans, this results in over 8 million possible combinations of chromosomes in each gamete.
- Fertilization: After meiosis, gametes from two parents combine during fertilization to form a zygote. The combination of genetic material from two individuals produces offspring with a unique genetic makeup. Fertilization, therefore, contributes significantly to genetic variability because it creates new combinations of alleles from two distinct sources.
On the other hand, binary fission is a form of asexual reproduction that produces genetically identical offspring, so it does not increase genetic variability.
In summary, crossing over, independent assortment, and fertilization are all crucial processes in sexual reproduction that contribute to genetic diversity. This genetic variability is important for the adaptability and evolution of populations over time.