Cell division：練習題

Where is meristem tissue found in plants, allowing them to differentiate into any type of plant cell throughout their life?

During the cell cycle, a cell must double its genetic material before it divides. Which of the following happens immediately after the DNA replicates but before the cytoplasm and cell membranes divide?

Which of the following correctly describes the process of meiosis in the human reproductive organs?

In human body cells, how are chromosomes normally found?

During the cell cycle, what must happen before a cell can divide by mitosis?

In mitosis, what happens to the copies of chromosomes that were made during the growth stage of the cell cycle?

During the cell cycle, what must happen to the DNA before the cell divides, and why is division by mitosis essential for a growing child?

A specific species of bacteria has a mean division time of \(20\) minutes. If a single bacterium begins dividing in a nutrient-rich agar plate, calculate the total number of bacteria present after exactly \(3\) hours.
Show your working and express your final answer in standard form.

Cells in multicellular organisms go through a series of stages called the cell cycle to produce new cells.

a) During the first stage of the cell cycle, the cell grows and increases the number of its sub-cellular structures. Name two such structures that the cell produces more of before it can divide.

b) Mitosis is the second stage of the cell cycle. Describe what happens to the chromosomes during this stage to ensure the new cells are genetically identical.

c) State one reason why cell division by mitosis is important for a growing child.

A student observes a bacterial population growing in a nutrient broth solution. The bacteria multiply by simple cell division (binary fission).

a) If the mean division time for this species of bacteria is \(30\) minutes and the initial population size is \(100\) cells, calculate the number of bacteria that will be present after \(4\) hours. Give your answer in standard form.

b) Describe two aseptic techniques the student should use to prepare an uncontaminated culture on an agar gel plate, and explain why each technique is necessary.