Question

Gametic cells from Drosophila melanogaster have 4 chromosomes and contain approximately 1.84 nanograms (ng) of nuclear DNA. Fill in the blanks of chromosome, and chromatid number. Also, amount of nuclear DNA that are found at each stage. MAKE SURE THE NUMBERS ARE SPECIFIC TO THE FRUIT FLY.

Stage of cell division	# chromosomes	# chromatids	Amount of nuclear DNA (ng)
End of Mitosis
End of Meiosis 1
End of Meiosis 2

Answer 1

Cell division starts with the replication of DNA. Replication takes place during the S-phase of cell cycle. After replication, the number of chromosomes is doubled and the chromatids remain the same number as before the replication.

During the mitosis, chromatids divide along with the chromosomes so the number of chromosomes number is same as chromatids. During meiosis, I chromatids numbers reduced to half because in meiosis I both the chromosomes attached to the chromatids moves towards the pole. Meiosis II is same as mitosis.

Stage of cell division	# chromosomes	# chromatids	Amount of nuclear DNA (ng)
End of Mitosis	8	8	3.68
End of Meiosis 1	8	4	3.68
End of Meiosis 2	4	4	1.84