Exercise 1: Cell Cycle Phases

Complete the following:

1. G1 phase is characterised by active _______ and _______ synthesis.
2. DNA replication occurs during _______ phase, doubling DNA content from _______ to _______.
3. After S phase, chromosome number remains _______ because sister chromatids are joined at the _______.
4. G2 phase involves synthesis of _______ for the spindle apparatus.
5. M phase consists of _______ + _______.
6. Cells in G0 phase include _______ and _______.

Answers: 1. RNA, protein 2. S, 2C, 4C 3. 2n, centromere 4. tubulin 5. karyokinesis (mitosis), cytokinesis 6. neurons, mature RBCs

Exercise 2: Prophase I Substages

Match the event to the correct substage (Leptotene/Zygotene/Pachytene/Diplotene/Diakinesis):

1. Crossing over: _______
2. Synapsis/pairing of homologues: _______
3. Chiasmata become visible: _______
4. Terminalization of chiasmata + nuclear membrane breaks down: _______
5. Chromosomes begin condensation (thin threads): _______

Answers: 1. Pachytene 2. Zygotene 3. Diplotene 4. Diakinesis 5. Leptotene

Exercise 3: Mitosis vs. Meiosis

Fill in the blank with "Mitosis" or "Meiosis" (I or II):

1. Produces 4 haploid cells: _______
2. Homologous chromosomes separate: _______ (anaphase ___)
3. Sister chromatids separate: _______ and _______ anaphase
4. Bivalents align at equatorial plate: _______ metaphase ___
5. Crossing over occurs: _______ (prophase ___, substage ________)

Answers: 1. Meiosis 2. Meiosis, anaphase I 3. Mitosis (anaphase), Meiosis II (anaphase II) 4. Meiosis, metaphase I 5. Meiosis, prophase I, pachytene

Exercise 4: Cytokinesis

1. Animal cells form a _______ furrow that proceeds _______.
2. Plant cells form a _______ from _______ vesicles, growing _______.
3. The direction of animal cell cytokinesis is called _______.
4. The direction of plant cell cytokinesis is called _______.

Answers: 1. cleavage, centripetally 2. cell plate, Golgi-derived, centrifugally 3. centripetal 4. centrifugal