Question

After crossing over, two chromatids are most likely to have a new sequence of DNA bases if they:

Answer 1

Answer:

C. are not sister chromatids.

Explanation:

Crossing over is a phenomenon which occurs between the non-sister chromatids of homologous chromosomes during meiosis I. Crossing over is the reason why there are so much variations amongst the individuals of a population which reproduce sexually. During crossing over, the DNA segments/sequences of non sister chromatids of homologous chromosomes are exchanged as a result of which non sister chromatids receive mixed DNA sequence at the end of meiosis-I.

Answer 2

The answer is C. Crossing over mostly occurs during meiosis I when sister chromosomes are lined up in the metaphase plate awaiting anaphase I where the sister chromosomes are pulled to separate daughter cells by spindle. It is during this period that the chromatids of the sister chromosomes come together at a point (chiasma)  and share genetic material in a process called crossing over.