Question

Ch. 9 Review - due Tuesday, 3 March 1) A bottlenose dolphin has 22 chromosomes in its somatic cells. How many chromosomes did the bottlenose dolphin inherit from each of its parents? How many chromosomes are in each of the bottlenose dolphin's gametes? How many chromosomes will be in each somatic cell of the bottlenose dolphin's offspring? 2) Draw a diagram showing the cell cycle and provide a brief description of the events that occur during each of the major "phases." Your drawing should include the following: interphase, G1 phase, S phase, G2 phase, M phase, and cytokinesis. 3) Fill in the following table by providing a short description of the major events that occur during each of the 5 phases of mitosis. Phase of Short description of major ! !

Answer 1

1. The organism has 22 chromosomes in its diploid somatic cell. It has inherited 11 chromosomes from each of the parents. In the gametes, there will be haploid number of chromosomes i.e. 11 chromosomes. In each somatic cell, there will be diploid number i.e. 22 chromosomes.

2. Cell cycle involves 2 major events i.e. Interphase and M phase. Interphase is divided into 3 phases which are G1, S and G2 respectively.

G1 stands for gap 1. In G1 phase, growth of the cell takes place. The cell is metabolically active and produces proteins that are required for DNA replication.

S stands for synthesis. In S phase, DNA replication occurs. The amount of DNA per chromosome gets doubled as DNA produces a copy of itself.

G2 stands for gap 2. In G2 phase, cell growth continues. The cell gets ready for the division to take place. The cell produces proteins that are required for cell division.

In M phase, actual cell division takes place. It involves karyokinesis i.e. division of nucleus which is followed by cytokinesis i.e. division of cytoplasm. M phase involves 4 stages i.e. Prophase, Metaphase, Anaphase and Telophase.

G2 Phase S Phase - M Preophase Metaphase Anaphase 18 Interphase Telephare are G1 Phase Hokina Cytokinesis

3.

Prophase-

- Condensation of chromosomes.

- Degeneration of nuclear membrane and nucleolus.

- Disappearance of cell organelles

Metaphase-

- Attachment of spindle fibers to the kinetochores of the chromosomes.

- Movement of chromosomes towards the metaphase plate.

- Alignment of chromosomes on metaphase plate.

Anaphase-

- Separation of sister chromatids of chromosomes.

- Chromatids start moving towards opposite poles.

Telophase-

- Chromatids gather at opposite poles.

- Decondensation of chromosomes to become chromatin fibers.

- Regeneration of nuclear membrane and nucleolus.

- Reappearance of cell organelles.

Cytokinesis-

- Division of cytoplasm to form two daughter cells.

- Formation of cell plate in case of plants.

- Formation of contractile ring in case of animals.

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