Cell cycle & mitosis

• Biologie
• Middelbare school
• vwo
• Leerjaar 4

Cell cycle & Mitosis

What are the three reasons why cells remain small?

1. Large cells have difficulty diffusing nutrients rapidly enough
2. As cells grow, their ratio of surface area to volume decreases
3. Transportation of wastes become a problem for larger cells
4. All of the above

What is the effect of surface area on diffusion?

The bigger the surface area, the faster the molecules will be evenly distributed over the available area

How many pairs of chromosomes are present in one human cell?

In growth of tissues cells divide/ double. What needs to be done with the DNA if a cell divides?

Learning objectives

• List and describe the steps of the cell cycle
• List and describe the phases of mitosis
•  Describe changes in number of chromosomes during the steps of the cell cycle and mitosis
• Describe changes in DNA content during the steps of the cell cycle and mitosis

Cell cycle

• Interphase:
    - G1-phase: growth, forming organelles
    - S-phase: DNA replication
    - G2-phase: growth, prep M-phase
•  Cell division: M-phase
     - Mitosis or Meiosis

S-phase

• DNA replication
• Chromosomes: DNA wrapped around proteins
• Centromere: point at which two chromatids connect
• Number of chromosomes = number of centromeres 
• Chromatid: half of a replicated chromosome
• n: number of different types of chromosomes in that species, n=23 for humans. We have chromosomes in pairs (except in gametes), remember Aa from inheritance last year.

The G1, S and G2 phase together make up the:

1. Cell cycle
2. Interphase
3. Mitosis
4. Growth phase

In which phase of the cell cycle are organelles formed?

1. M phase
2. G1 Phase
3. G2 Phase
4. S phase

What is the structure called that connects the chromatids?

1. Centriole
2. Centromere
3. Controsome

Which applies?

1. 4 chromosomes, 8 chromatids
2. 8 chromosomes, 8 chromatids
3. 8 chromosomes, 4 chromatids
4. 8 chromosomes, 16 chromatids

Which applies?

1. 4 chromosomes, 8 chromatids
2. 8 chromosomes, 8 chromatids
3. 8 chromosomes, 4 chromatids
4. 8 chromosomes, 16 chromatids

M-phase

• Cell division
• Two options:
    - Mitosis: creating exact copies of the original cell for growth and repair
    - Meiosis: creating cells with half the number of chromosomes for reproduction (the gametes)

Mitosis

One cell will split in two exact copies

2n (46) --> 2n + 2n

Prophase

• Chromosomes condense: each has two chromatids
• Nuclear membrane starts breaking down
• Spindle apparatus appears 

Metaphase

• Centromeres lined up on the equator
• Each chromatid attached to a spindle fibre 

Anaphase

• Separation of the sister chromatids 
• Sister chromatids move to opposite poles, now called chromosomes

Telophase

• Chromosomes have reached poles
• Nuclear membranes start forming
• Chromosomes uncoil, become less visible 

Cytokinesis

• Actual splitting of cytoplasm 

Homework

• Watch the two video's below
• Complete the worksheet Mitosis 
• Study the Quizlet words: https://quizlet.com/_98nhb9?x=1qqt&i=134sd6  

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