| 1 | 2 | 3 | 4 | 5 | 6 |
| 7 | 8 | 9 |
Question 1
Mitosis and meiosis are two different types of cell division. The algal species Ulva lactuca uses both types of cell division. |
a) | Name the phase of meiosis in which single chromosomes line up on the equator of the cell.
|
b) | Describe two differences between mitosis and meiosis.
|
c) | Explain why the process of meiosis is important in the life cycle of Ulva lactuca.
|
d) | Crossing over is a process that occurs within meiosis. Describe how crossing over leads to genetic variation.
|
|
Question 2
The table below shows some of the events that take place in mitosis and meiosis. |
a) | Complete the table by placing a tick if the statement describes an event that occurs in the type of cell division or a cross if the event does not occur.
|
b) | Name the type of cell division that results in the production of gametes.
|
c) | Explain why meiosis is described as a reduction division.
|
d) | Describe the events that take place in anaphase I of meiosis.
|
|
Question 3
The diagram below shows a summary of meiosis.
|
a) | Name one event that takes place in the second division, but not the first division.
|
b) | Explain the appearance of one of the chromosomes in cell A.
|
c) | Name two processes that give rise to genetic variation, including the phase of meiosis each process takes place in.
|
d) | Apart from increasing genetic variation, explain why meiosis is important for sexually reproducing organisms.
|
|
Question 4
A garden snail body cell contains 54 chromosomes. |
a) | Give the number of chromosomes in a garden snail’s egg cell.
|
b) | Give two reasons why the egg cells produced by the same garden snail are genetically different from one another.
|
c) | In certain lab conditions, female garden snails can be treated so that they produce diploid egg cells. Give the number of chromosomes in body cells of the offspring produced from lab-treated female garden snails and untreated male garden snails.
|
d) | The offspring produced from lab-treated female garden snails and untreated male garden snails are sterile. Explain why.
|
|
Question 5
Edward’s syndrome is a genetic condition caused by a mutation that affects the number of chromosomes in each body cell. The diagram below shows the chromosomes from one of the cells of a male with Edward’s syndrome. |
a) | What is the effect of Edward’s syndrome on the chromosomes of this cell?
|
b) | Describe how the change in chromosome number in Edward’s syndrome may be produced.
|
c) | Explain why this chromosome mutation is found in all body cells of individuals with Edward’s syndrome.
|
d) | Some cancers that develop later in life are caused by chromosome mutations. Suggest why these cancers are unlikely to be the result of errors in meiosis.
|
|
Question 6
The diagram below shows a pair of homologous chromosomes at the start of meiosis. The letters represent the alleles found on each chromosome. |
a) | Describe and explain the appearance of the chromosomes shown above.
|
b) | What are homologous chromosomes?
|
c) | The diagram below shows the same chromosomes in four of the gametes produced after meiosis. Explain how gametes Y and Z have been produced.
|
d) | Most of the gametes contained the allele combinations found in gametes W and X. Suggest why only a few gametes contained the same combinations as cells Y and Z.
|
|
Question 7
The diagram below shows a cell with 8 chromosomes. |
a) | This cell divides by meiosis to form four cells. Draw a diagram to show the chromosomes in one of these four cells.
|
b) | How many different types of gametes could be produced from this cell as a result of different combinations of maternal and paternal chromosomes?
|
c) | Chromosomes contain alleles. What is an allele?
|
d) | Meiosis increases genetic variation. Describe and explain the events causing this variation.
|
|
Question 8
The life cycle of a moss plant involves diploid and haploid organisms. The diagram below shows the life cycle of a typical moss plant. The gametophyte contains haploid cells and produces both sperm and egg cells. The sporophyte contains diploid cells and produces spores which disperse through the air. These spores germinate and grow into gametophytes. |
a) | Which letter from A, B, or C shows where meiosis occurs in the life cycle of the moss plant?
|
b) | Explain how the chromosome number changes during meiosis.
|
c) | The zygote forms a sporophyte using the process of mitosis. The haploid gametophyte of one moss species contains 20 chromosomes. Calculate the number of DNA strands present in the nucleus of a zygote immediately after interphase.
|
d) | Genetic diversity is increased by crossing over in the process of meiosis. Describe how crossing over occurs and explain how it affects genetic diversity.
|
|
Question 9
The diagram below shows an example of a cell undergoing a type of cell division. |
a) | Name the type of cell division and the stage shown in the diagram above.
|
b) | Describe the evidence for your answer to part a.
|
c) | Another stage of meiosis is metaphase I. Explain how events taking place during metaphase I increase genetic variation.
|
|
| 1 | 2 | 3 | 4 | 5 | 6 |
| 7 | 8 | 9 |