Question

Describe the steps of mitosis and create a mnemonic device to remember it with.

Compare and contrast two organelles

Answer 1

Ans- Mitosis is a process of cell division in which a single cell divides into two daughter cells. It consists of 5 stages which are described below-

1. Prophase- During this phase, the nuclear envelope breaks down and mitotic spindle formation takes place at the edges of the dividing cell which helps in division of the cell during the elongation. During early prophase, the chromosomes condense and during late prophase, nuclear envelope breaks down and microtubules reach from poles to the centre of cell. Other organelles like endoplasmic reticulum, golgi bodies also disappear during this phase.

2. Metaphase- The pairs of condensed chromosomes line up along the equator of the elongated cell. During prometaphase, nuclear membrane disappears and microtubules rapidly assemble and disassemble seeking out attachment sites at chromosome kinetochores. At the end of prometaphase, kinetochores on sister chromatids are connected by microtubules to opposite poles of spindle. During metaphase, chromosomes attain most compact size when they arrange at the equator.

3. Anaphase- During this phase, there is separation of sister chromatids. During the first part of anaphase, kinetochore microtubules shorten and chromosomes move towards opposite poles. During the second part, spindle poles separate as non kinetochore microtubules move past one another.

4. Telophase- This is the last phase where chromosomes reach the poles, nuclear envelope forms again and chromosomes begin to decondense. It is followed by cytokinesis where division of cytoplasm takes place to form two daughter cells. These daughter cells are genetically identical.

Mnemonic to remember the stages of prophase-

1. Interphase- I mmediately

2. Prophase- P lease

3. Metaphase- M eet

4. Anaphase- A t

5. Telophase- T he

6. Cytokinesis-  C ircus

Ans-2. Compare and contrast two organelles-

Organelle 1- Chloroplast

Organelle 2- Mitochondria

Similarities-

1. Both are enclosed by two membranes.

2. Both have their own DNA.

3. Both are semi-autonomous organelles.

4. They are involved in ATP production.

5. Both have electron transport chain

Differences-

1. Both animal and plant cells have mitochondria bit only plant cells have chloroplasts.

2. Mitochondria do not convert light energy into chemical energy.

3. Chloroplast have thylakoids inside which have pigments while there are no pigments in mitochondria.

4. The space within mitochondria is called matrix while in chloroplasts it is called stroma.

5. Mitochondria generate ATP from glucose during cellular respiration, chloroplasts generate ATP from light to create glucose for storage.