Binary fission and mitosis

Question 1

Stages of the cell cycle

Answer 1

1. Interphase - no division takes place, 90% of the cell cycle
   - G1 (first growth) - proteins are synthesised and produces to form new organelles
   - S (synthesis) - DNA replication
   - G2 (second growth) - organelles grow and divide, energy stores increased
2. Nuclear division - nucleus divides into 2 (by mitosis) or 4 (by meiosis) nuclei
3. Cell division - cell divides into 2 (by mitosis) or 4 (by meiosis) cells

Question 2

mitosis vs meiosis

Answer 2

mitosis
- produces 2 diploid daughter cells
- same number of chromosomes as the parent

meiosis -
- produces 4 haploid daughter cells
- half the number of chromosomes of the parent cell

Question 3

Stages of mitosis

Answer 3

1. Prophase - chromosomes become visible, nuclear envelope disintegrates
2. Metaphase - spindle forms, chromosomes line up in the middle
3. Anaphase - spindle fibres attach, chromatids are pulled to opposite poles
4. Telophase - nuclear envelope reforms

Question 4

What mitosis is needed for?

Answer 4

1. growth - forming a new organism from a gamete
2. differentiation - forming tissues, groups of cells that perform a specific function
3. repair - replacing damaged or dead cells

Question 5

How do eukaryotic and prokaryotic cells divide?

Answer 5

eukaryotic - by mitosis
prokaryotic - by binary fission

Question 6

process of binary fission

Answer 6

1. One copy of the origin moves to the other end of the cell
2. Chromosome replicates, now having two origins
3. The other copy of the origin will move to the opposite end of the cell
4. Replication finishes, plasma membrane grows inwards, cell wall deposited

• each daughter cell has a copy of the circular DNA
• each daughter cell has a variable number of plasmids

Question 7

conjugation / horizontal gene transmission process

Answer 7

1. One cell produces a thin projection that forms a conjugation tube between two cells
2. Circular piece of DNA, plasmid, is replicated in the donor cell
3. Plasmid is broken to make it linear
4. Linear DNA is passed through the conjugation tube
5. Linear DNA received forms a circle - new plasmid

*contact between cells is brief, so only a portion of DNA is transferred

Question 8

Horizontal gene transmission -

Answer 8

Horizontal gene transmission - DNA in the form of genes is passed form one species to another species

Question 9

Investigating mitosis practical

Answer 9

1. samples taken from the root tip - cells go through mitosis most often
2. toluidine blue dye - to stain the chromosomes and make them visible
3. acetic arcein dye no longer used - hazardous and damages DNA and cells
4. sample soaked in HCl acid - breaks down tissue to form a single layer of cells
5. cover slide pushed down but not sideways - to squash and spread out the sample, but not damage the cells or chromosomes

Question 10

mitotic index =

Answer 10

mitotic index = number of cells in mitosis / total number of cells