The diagram shows an outline of the mitotic cell cycle.
Which numbered stages of the cell cycle include a period of time when each chromosome consists of sister chromatids joined by a centromere?
▶️ Answer/Explanation
Ans: A
Sister chromatids are present from DNA replication (S phase, part of 1) until anaphase (part of 2). Stage 1 (interphase) includes S phase, and stage 2 (mitosis) includes phases before chromatid separation. Thus, A (1 and 2) is correct.
The photomicrograph shows cells in an onion root tip.
Which labelled cells are in anaphase, metaphase and prophase?
▶️ Answer/Explanation
Ans: D
In mitosis: Prophase (X) shows condensed chromosomes, Metaphase (Y) has chromosomes aligned at equator, and Anaphase (Z) shows chromosomes separating. The correct sequence is Z (anaphase), Y (metaphase), X (prophase), making D the right answer.
Which process does not involve mitosis?
▶️ Answer/Explanation
Ans: B
Unicellular organisms grow by increasing their cell size, not through mitosis. Mitosis is involved in asexual reproduction (A), tissue repair (C), and cell replacement (D) which all require cell division. Therefore, the correct answer is B.
Which processes occur in bone marrow cells that are in a mitotic cell cycle?
- Phosphate groups bind to ADP molecules to form ATP.
- Bonds form between nucleotides in a DNA strand.
- Hydrogen bonds form between tRNA anticodons and mRNA codons.
▶️ Answer/Explanation
Ans: A
1: ATP formation occurs continuously for energy. 2: DNA replication occurs in S-phase. 3: Protein synthesis (translation) occurs throughout interphase to produce proteins needed for cell division. Thus all three processes occur during the mitotic cycle.