Lecture 21: Mitosis

Question 1

Know the definition of cell division and describe the two important requirements of this process.

Answer 1

The process by which a single cell becomes two daughter cells.
Important Requirements
1. Each daughter cell must receive the full complement of genetic material from the parent cell
2. The parent cell must be large enough to divide in two and provide sufficient cytoplasmic components to the daughter cells

Question 2

Know the process of Binary fission and the type of cell in which this process occurs

Answer 2

.

Question 3

Compare cell division in eukaryotes vs prokaryotes

Answer 3

Eukaryotic cells:

• genome is large and linear
• DNA in the nucleus

Prokaryotic cells:

• genome is small and circular
• DNA in the cytoplasm

Question 4

Know and describe the two distinct stages of the cell cycle; including which stage a cell spends the most amount of time in

Answer 4

Two distinct stages:
1. M phase: the time during which the parent cell divides into two daughter
cells
2. Interphase: the time between M phases

Question 5

Describe interphase, including the four phases that comprise it.

Answer 5

G1 (first “gap”) phase:
the size and protein content of the
cell increases in preparation for the S phase
regulatory proteins are made and activated

S (Synthesis) phase:
the entire DNA content in the nucleus of the cell is replicated

G2 (second gap) phase:
the cell prepares for mitosis and cytokinesis

G0 phase:
- differs from G1 because there is no preparation taking place for cell division
- this phase is present in cell types that do not actively divide: liver and nerve cells

Question 6

Describe how DNA is organized in eukaryotic cells

Answer 6

• Eukaryotic DNA Organization DNA is organized with histones and
  other proteins into chromosomes
• Cells of the human body contain 46
  chromosomes (23 pairs)
  Humans have 22 pairs of homologous chromosomes and 1 pair of sex chromosomes
• Homologous chromosomes: carry the same set of genes, one from the mother and one from the father
  • Sex chromosomes: X and Y
  • Cells with one complete set of chromosomes are haploid, cells with two complete sets are diploid

Question 7

Know and describe the 5 stages of Mitosis

Answer 7

1. Prophase
   Chromosomes condense, centrosomes radiate microtubules and migrate to opposite poles.
2. Prometaphase
   Microtubules of the mitotic spindle attach to chromosomes.
3. Metaphase
   Chromosomes align in middle of cell.

4. Anaphase
Sister chromatids (which become individual chromosomes when the centromere splits) separate and travel to opposite poles.

5. Telophase
   Nuclear envelope reforms and chromosomes decondense.