11: Cell Cycle and Division - Problems Flashcards
(DSE 2014 IB Q3)
Before the early 20th century, scientists believed that cell division results in the loss of genetic material so that each cell in a multicellular organism would contain only the genetic material specific to its particular cell type.
In 1902, Hans Spemann used a fine hair to separate the cells of a two-celled amphibian embryo, and found that each cell was able to develop into a complete organism.
Explain why Spemann’s experiment disprove the early belief about cell division. (1)
Since each of the separated cells were able to develop into an complete organism, this shows that a whole set of genetic material is present in each cell.
(DSE 2014 IB Q3)
Before the early 20th century, scientists believed that cell division results in the loss of genetic material so that each cell in a multicellular organism would contain only the genetic material specific to its particular cell type.
In 1902, Hans Spemann used a fine hair to separate the cells of a two-celled amphibian embryo, and found that each cell was able to develop into a complete organism.
Using the current understanding about cell division, explain how genetic material is preserved in mitosis. (3)
Genetic material is duplicated right before cell division.
The chromosomes in duplicated state will line up at the middle part of the cell for separation.
Each sister chromatid of the chromosomes in the duplicated state will then separate and divide equally into each daughter cell, so each daughter cell has a complete set of genetic material identical to that of the parent cell.
A tumour is a mass of abnormal cells resulting from uncontrolled cell division. A doctor investigated a sample of tissue X which is suspected to be a tumour. The table below shows the percentages of cells at different stages of the cell cycle in X and another sample of the same type of the tissue which is normal (Y).
Suggest how the doctor could distinguish the cells at interphase from the cells at other stages. (1)
Chromosomes are not visible in the cells at interphase.
A tumour is a mass of abnormal cells resulting from uncontrolled cell division. A doctor investigated a sample of tissue X which is suspected to be a tumour. The table below shows the percentages of cells at different stages of the cell cycle in X and another sample of the same type of the tissue which is normal (Y).
Cells in tissue Y take approximately 24 hours to complete one cell cycle. Calculate the relative time the cells in tissue Y spend at interphase. (2)
The relative time the cells spend in interphase:
85/100 x 24 = 20.4 hours
A tumour is a mass of abnormal cells resulting from uncontrolled cell division. A doctor investigated a sample of tissue X which is suspected to be a tumour. The table below shows the percentages of cells at different stages of the cell cycle in X and another sample of the same type of the tissue which is normal (Y).
Explain whether tissue X is likely to be a tumour and support your answer with information given in the table. (2)
Yes.
The percentage of dividing cells in tissue X (60%) is much higher than that in tissue Y (17%).
This means cells in tissue X may be dividing more often than those in normal tissue.
A tumour is a mass of abnormal cells resulting from uncontrolled cell division. A doctor investigated a sample of tissue X which is suspected to be a tumour. The table below shows the percentages of cells at different stages of the cell cycle in X and another sample of the same type of the tissue which is normal (Y).
An inhibitor targeting an enzyme which is involved in the process of DNA replication can be used to treat tumour. Suggest how the inhibitor works. (2)
When DNA replication is inhibited, cells cannot divide.
This stops the formation of new tumour cells.
The diagram below shows a plant cell undergoing a type of cell division.
Which type of cell division is the cell undergoing? Support your answer with tow pieces of evidence from the diagram.
Meiotic cell division
Homologous chromosomes paired up.
Crossing over has occurred between non-sister chromatids of homologous chromosomes.
The diagram below shows a plant cell undergoing a type of cell division.
In terms of chromosome number in the daughter cells produced, explain the importance of this type of cell division.
Meiotic cell division reduces the chromosome number in the daughter cells to half.
The diploid number of chromosomes can be restored when the male gamete and the female gamete fuse during fertilisation.
This allows a species to preserve a constant number of chromosomes from generation to generation.
(DSE 2015 IB Q2)
The photomicrograph below shows the appearance of genetic materials at two different stages of the cell cycle.
With reference to the appearance of the genetic materials shown in the photomicrograph, explain at which stage is transcription more likely to take place.
Stage A,
since the genetic materials are dispersed and loosely packed, indicating that the DNA molecules are ready fro transcription.
(DSE 2015 IB Q2)
Mitosis produces 2 daughter cells but meiosis produces 4 daughter cells. Explain the difference in the number of daughter cells in mitosis and meiosis. (1)
Mitosis involves one division but meiosis involves two divisions.
(DSE 2015 IB Q2)
Mitosis produces diploid daughter cells but meiosis produces haploid daughter cells. Explain the difference in the DNA content in mitosis and meiosis. (1)
Homologous chromosomes pair up and are separated into each daughter cell in meiosis but not in mitosis.
Mitosis and meiosis are important processes that ensure the continuity of life. Contrast thee two processes and state the significance of their differences. (8+3)
Differences: (3)
There is pairing of homologous chromosomes along the equatorial plane in first division of meiosis but no such process in mitosis.
The pairs of homologous chromosomes segregate into the daughter nuclei during the first meiotic cell division.
Mitosis involves one division only but meiosis involves two divisions.
Significance: (5)
Mitosis: The daughter cells resulted from mitosis are genetically identical to the parent cell which is important for growth and asexual reproduction.
Meiosis:
The daughter cells formed after meiosis contain one member of each homologous pairs.
The daughter cells / gametes formed in resulted from meiosis contain half the genetic content of the parent cell, such that the amount of genetic content can be restored after fertilisation.
Random segregation of homologous chromosomes results in variations between gametes formed in meiosis.
Crossing over may occur in meiosis, the exchange of genetic materials between non-sister chromatids gives rises to new genetic combinations.
