Question

the cell cycle
name:

1. define:

chromosome:
sister chromatid:
centromere:
equator:
zygote:
mutation:

1. do cells reproduce sexually or asexually? defend your answer.
2. in which phase do cells spend most of their life?
3. what do they do in that phase?
4. at which point in interphase are cells officially committed to reproduction?
5. what are the 4 steps of mitosis?
6. how is cytokinesis different in plant and animal cells?
7. what happens if a cell divides with damages present in its dna?

Explanation:

1. Definitions:

• Chromosome: A condensed structure of DNA and proteins that carries genetic information, visible during cell division.
• Sister Chromatid: One of two identical copies of a single chromosome formed after DNA replication, joined at the centromere.
• Centromere: The constricted region of a chromosome that holds sister chromatids together and attaches to spindle fibers during division.
• Equator: The central plane of a cell where chromosomes align during metaphase of mitosis/meiosis.
• Zygote: A diploid cell formed by the fusion of two haploid gametes (sperm and egg), the first cell of a new organism.
• Mutation: A permanent change in the DNA sequence of a cell's genome, which can alter traits.

1. Cell Reproduction: Cells can reproduce both ways. Body (somatic) cells use asexual mitosis to make identical copies for growth/repair. Gametes use sexual meiosis to make genetically unique cells for reproduction.
2. Longest Cell Cycle Phase: Interphase is the longest phase, making up ~90% of the cell cycle.
3. Activity in Interphase: Cells grow, perform their specialized functions, and replicate their DNA in preparation for division.
4. Commitment Point in Interphase: The Restriction Point (R point) in the G1 phase; after this, the cell will proceed to complete the cell cycle.
5. Steps of Mitosis: The four sequential steps are prophase, metaphase, anaphase, and telophase.
6. Cytokinesis Difference: Animal cells form a cleavage furrow (pinching the cell membrane inward) to split the cytoplasm; plant cells form a cell plate (new cell wall material) that grows to divide the cell.
7. Division with Damaged DNA: Damaged DNA can lead to mutations in daughter cells, which may cause abnormal cell function, uncontrolled growth (cancer), or cell death if the damage is too severe.

Answer:

1.

• Chromosome: A condensed DNA-protein structure carrying genes.
• Sister Chromatid: Identical replicated chromosome copy, linked at centromere.
• Centromere: Chromosome region holding chromatids together.
• Equator: Central cell plane for metaphase chromosome alignment.
• Zygote: Diploid cell from sperm-egg fusion.
• Mutation: Permanent DNA sequence alteration.

1. Cells can reproduce both asexually and sexually. Somatic cells use asexual mitosis to produce identical cells for growth and repair; gamete-forming cells use sexual meiosis to produce genetically unique cells for sexual reproduction.
2. Interphase
3. Cells grow, carry out their normal functions, and replicate their DNA.
4. The Restriction Point (R point) in the G1 phase of interphase.
5. Prophase, metaphase, anaphase, telophase
6. Animal cells form a cleavage furrow to pinch the cell into two; plant cells form a cell plate that develops into a new cell wall to divide the cell.
7. Damaged DNA can lead to heritable mutations in daughter cells, potentially causing abnormal cell behavior, uncontrolled cell growth (cancer), or cell death.