5.01 Growth and Reproduction of Cells

Question 1

Describe the role of cell division in growth and reproduction. (4 marks)

Mark Scheme:

1. Cell division is essential for growth and reproduction in all living organisms. (1 mark)
2. During growth, cell division increases the number of cells, allowing organisms to develop and repair tissues. (1 mark)
3. In reproduction, cell division produces genetically identical daughter cells through mitosis, ensuring genetic continuity. (1 mark)
4. Precision during cell division prevents genetic loss and maintains cellular function. (1 mark)

Question 2

Explain the importance of the nucleus in cell division. (5 marks)

Mark Scheme:

1. The nucleus contains DNA, which carries the genetic instructions for cellular functions. (1 mark)
2. Before cell division, the nucleus must divide to ensure each daughter cell receives a complete set of genetic material. (1 mark)
3. DNA within the nucleus ensures that genetic instructions are transferred accurately to the daughter cells. (1 mark)
4. This transfer maintains the genetic identity of all body cells in multicellular organisms, except gametes. (1 mark)
5. Errors in nuclear division could lead to genetic disorders or loss of essential cellular functions. (1 mark)

Question 3

Outline the main stages of the mitotic cell cycle and their significance. (6 marks)

Mark Scheme:

1. Interphase: The cell grows, and DNA is replicated to prepare for division. (1 mark)
2. Mitosis: The nucleus divides, ensuring each daughter cell receives an identical set of chromosomes. (1 mark)
3. Cytokinesis: The cytoplasm divides, forming two genetically identical daughter cells. (1 mark)
4. The mitotic cycle ensures genetic continuity by transferring identical genetic material to daughter cells. (1 mark)
5. This process starts with the zygote and produces all body cells through repeated divisions. (1 mark)
6. Mitosis supports growth, tissue repair, and asexual reproduction in multicellular organisms. (1 mark)

Question 4

What is mitosis, and how does it ensure genetic continuity? (5 marks)

Mark Scheme:

1. Mitosis is a nuclear division process that produces two identical nuclei for daughter cells. (1 mark)
2. During mitosis, chromosomes are replicated and equally distributed between the two daughter nuclei. (1 mark)
3. This ensures that each daughter cell receives an identical set of genetic material. (1 mark)
4. Genetic continuity is maintained, allowing cells to carry out the same functions as the parent cell. (1 mark)
5. Mitosis prevents genetic loss or errors during division, supporting normal growth and repair. (1 mark)

Question 5

Explain how body cells in multicellular organisms maintain genetic identity. (6 marks)

Mark Scheme:

1. All body cells, except gametes, originate from the zygote formed by the fusion of parental gametes. (1 mark)
2. The zygote divides repeatedly through mitosis, producing genetically identical daughter cells. (1 mark)
3. During mitosis, DNA replication ensures each daughter cell receives an identical copy of genetic material. (1 mark)
4. The genetic instructions in DNA direct the same cellular functions in all body cells. (1 mark)
5. The precision of mitosis maintains the genetic identity across all cells. (1 mark)
6. This uniformity is crucial for coordinated functioning in multicellular organisms. (1 mark)

Question 6

Describe the relationship between the zygote, mitosis, and the formation of the human body. (5 marks)

Mark Scheme:

1. The zygote is the single cell formed by the fusion of sperm and egg gametes during fertilization. (1 mark)
2. The zygote divides repeatedly through mitosis, producing genetically identical cells. (1 mark)
3. These divisions lead to the formation of approximately 30 trillion cells in the human body. (1 mark)
4. Mitosis ensures that all cells contain identical genetic material, derived from the zygote. (1 mark)
5. This process supports growth, development, and tissue specialization in the human body. (1 mark)

Question 7

What are the consequences of errors during mitosis for genetic continuity? (4 marks)

Mark Scheme:

1. Errors during mitosis can result in unequal distribution of chromosomes to daughter cells. (1 mark)
2. This may lead to genetic disorders or the formation of non-functional cells. (1 mark)
3. Loss or duplication of genetic material can disrupt cellular functions or cause cell death. (1 mark)
4. In multicellular organisms, such errors could impair tissue repair, growth, or lead to diseases like cancer. (1 mark)

Question 8

Explain why mitosis is crucial for growth and repair in multicellular organisms. (5 marks)

Mark Scheme:

1. Mitosis increases the number of cells, enabling tissues to grow and expand. (1 mark)
2. It replaces damaged or dead cells with new, genetically identical cells. (1 mark)
3. The replication and transfer of identical DNA during mitosis ensure that new cells can perform the same functions as the original cells. (1 mark)
4. This process supports the repair of injuries and the maintenance of tissue integrity. (1 mark)
5. Mitosis also ensures that the organism retains its genetic identity throughout its lifetime. (1 mark)

Question 9

Discuss the significance of DNA replication before mitosis. (4 marks)

Mark Scheme:

1. DNA replication occurs during interphase, before mitosis begins. (1 mark)
2. This ensures that each daughter cell receives an identical copy of genetic material. (1 mark)
3. Accurate replication is critical to maintaining the genetic continuity of cells. (1 mark)
4. Errors in DNA replication could lead to mutations, potentially causing diseases or functional defects. (1 mark)

Question 10

How does the mitotic cell cycle contribute to the genetic uniformity of body cells? (5 marks)

Mark Scheme:

• The mitotic cycle consists of DNA replication, mitosis, and cytokinesis, producing two identical daughter cells. (1 mark)
• During mitosis, chromosomes are duplicated and distributed evenly to each nucleus. (1 mark)
• This ensures that all body cells have the same genetic material as the parent cell. (1 mark)
• Genetic uniformity enables consistent cellular functions across different tissues. (1 mark)
• The repeated mitotic cycle from the zygote ensures the entire organism shares the same genetic identity. (1 mark)