Question

Cattle germ cell has a diploid number of 60 chromosomes. Complete the following table by stating the number of cells, the number of chromatids, and the number of chromosomes at the end of each of the following stages of meiosis and mitosis. (3 marks) B I E E U S X2 x C I с ✓c <> XQ Meiosis Mitosis Prophase Prophase II Telophase Number of Cells Number of Chromatids N/A Number of Chromosomes Formation of Twins

Answer 1

Okay, remember that a cell will duplicate the number of chromatides in replication, that would be to have 120 chromatides (2 per each chromosome) when replciation is over, and then mitosis will divide this number by 2 to give each daughter cell one of these 60 chromosomes. Diploidy is never lost in mitosis.

Now, meiosis will actually lose diploidy, and this happens since the first division (meiosis I), in this stage the homologous chromosomes will segregate thus producing daughter cells with only 30 chromosomes but 60 chromatides. The chromatides will segregate in Meosis II and this will bring cells with 30 chromosomes and 30 chromatides.

Now, let us fill the table:

Meiosis Mitosis Prophase Prophase II Telophase Number of Cells 1 2 2 Number of Chromatids 120 60 per cell N/A Number of Chromosomes 60 30 per cell 60 per cell

Another thing to have in mind when solving this kind of problems is that segregation occurs in Anaphase, that means Prophase and Metaphase occur previously to segregation.