IB Biology HL (HIGHER level)- 2024 – Practice Questions- All Topics
Topic 1.6 Introduction to cells
Topic 1 Weightage : 8 %
All Questions for Topic 1.6 –Cell Cycle, Interphase, DNA Supercoiling, Mitosis, Cytokinesis, Mitotic Index, Cyclins, Cancer Development, Smoking and Cancer, Cell Checkpoints, Cell Death
Question
Students examined micrographs and counted cells in the different stages of mitosis as well as those cells with no visible chromosomes.
The table shows their results.
Stage | Prophase | Metaphase | Anaphase | Telophase | Interphase |
Number of cells | 10 | 3 | 2 | 5 | 30 |
What is the mitotic index?
A. 0.2
B. 0.4
C. 0.6
D. 0.7
▶️Answer/Explanation
Ans: B
The mitotic index is a measure of the fraction of cells undergoing mitosis. It is calculated by dividing the total cells undergoing mitosis by the total cells visible Mitotic index = number of cells with visible chromosomes ÷ total number of cells
Mitotic index = (prophase + metaphase + anaphase + telophase) ÷ total number of cells
Question
What would show that a person has developed metastatic cancer?
A Alveolus cells forming a tumour in the lungs
B Cancer cells producing the skin pigment melanin in the liver
C A tumour in the prostate gland increasing levels of prostate-specific antigen
D Cancerous lymphocytes in blood plasma
▶️Answer/Explanation
B
When cancer cells produce melanin in the liver as a result of metastatic cancer, it initiates a signaling cascade involving cytokines, growth factors, bioactive lipids, and reactive oxygen and nitrogen species produced by the cancer cell, the endothelium, and also by different immune cells. Liver metastases are commonly detected in a range of malignancies including colorectal cancer (CRC), pancreatic cancer, melanoma, lung cancer and breast cancer.
Question
The micrograph shows some onion (Allium cepa) cells undergoing mitosis.
What is the mitotic index, taking into account all visible nuclei?
A. 0.1
B. 0.2
C. 0.4
D. 0.6
▶️Answer/Explanation
Ans:B
The mitotic index is a measure of the fraction of cells undergoing mitosis, It is calculated by dividing the total cells undergoing mitosis by the total cells visible
Mitotic index – number of cells with visible chromosomes total number of cells
Mitotic index(prophase metaphase anaphase+ telophase) total number of cell
Here 10 nuclei are visible and 2 of those are dividing, so mitotic index as per as given data will be (2+10-0.2) or 20%
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