During crossing-over
Select one:
a. chromosomes switch poles.
b. chromatin becomes chromosomes.
c. chromosomes become chromatin.
d. chromatids exchange segments of genetic material.
e. mitosis becomes meiosis.
The correct answer and explanation is:
The correct answer is d. chromatids exchange segments of genetic material.
Explanation:
Crossing-over is a key event that occurs during prophase I of meiosis, the type of cell division that reduces the chromosome number by half to produce gametes (sperm and eggs). This process plays an important role in genetic diversity.
During crossing-over, homologous chromosomes, which are chromosomes that have the same genes but may have different alleles, come together in pairs. These chromosomes are made up of sister chromatids (identical copies of the same chromosome). In the process of crossing-over, sections of chromatids from one chromosome are exchanged with corresponding sections of the chromatid from the other homologous chromosome. This results in new combinations of alleles, contributing to genetic variation in the offspring.
The process of crossing-over occurs at specific regions called chiasmata. When crossing-over happens, the chromatids physically break and then reconnect, but in a different orientation, so parts of one chromatid swap with parts of the other chromatid. This process leads to chromatids that carry a mixture of genetic information from both the maternal and paternal chromosomes.
Crossing-over is critical in increasing genetic variation because it ensures that each gamete carries a unique set of genetic instructions. This is important for evolution and survival as it allows populations to adapt to changing environments.
In summary, crossing-over involves the exchange of segments of genetic material between chromatids of homologous chromosomes, leading to genetic recombination and increased diversity in offspring.