Differiente Meosis And Mitosis

Question 1

What are the 5 stages of mitosis?

Answer 1

1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
5. Cytokinesis

Question 2

Define the stages of cell cycle

Answer 2

G1 phase: cell grows in size and volume
S phase (DNA replication): chromosome replicate, forming two identical copies of DNA. Therefore, following the S phase, the cell now has 92 chromosomes and is nearly ready to divide by mitosis.
G2 phase: further growth and preparation for cell division
M phase: mitosis

Question 3

Explain prophase

Answer 3

Replicated chromatin become tightly coiled.
Each of the original 46 chromosomes is paired with its copy in a double chromosome unit.
Two chromatids are joined to each other at the centromere.
Mitotic apparatus appears, this consists of two centrioles separated by the mitotic spindle, which is formed from microtubles.
The centrioles migrate, one to each end of the cell, and the nuclear envelope disappears.

Question 4

Explain metaphase

Answer 4

The chromatids align on the centre of the spindle, attached by their centromeres.

Question 5

Explain anaphase

Answer 5

The centromeres separate, and one of each pair of sister chromatids (now called chromosomes agains) migrates to each end of the spindle as the microtubles that form the mitotic spindle shorten.

Question 6

Explain telophase

Answer 6

The mitotic spindle disappears, the chromosomes uncoil and the nuclear envelope reforms.

Question 7

Explain cytokinesis

Answer 7

The physical process where the cell divides the cytoplasm of a parental cell into two daughter cells

Question 8

Describe meiosis

Answer 8

DNA replication occurred beforehand, so each pair of chromosomes is now four chromatids, and they gather together into a tight bundle.

The chromosomes are very tightly associated and so it is possible for them to exchange genes. This is the process of crossing over and results in the four chromatids acquiring different combinations of genes.

Following crossing over, the pairs of chromosomes then separate in preparation for the first meiosis division, and transfer of material and paternal chromosomes to either daughter cell is random.
This means that two daughter cells have an unpredictable assortment of maternal and paternal DNA, giving rise to a huge number of possible combinations of chromosomes in them.

Each pair of chromosomes separated and one travel to each end of the cell, guided by a spindle, as in mitosis, producing two genetically unique diploid daughter cells.

For a gamete to be produced, the amount of genetic material present in the two daughter cells following the first meiosis divisions must be halved.
This is accomplished by the second division.

The centromeres separate and the two sister chromatids travel to opposite ends of the cell, which then divides. Each of the four haploid daughter cells now has only one chromosome from each original pair.

Fusion with another gamete creates a zygote (fertilised ovum), a diploid that can go to grow and develop into a human being by mitosis.