3.10 The Cell Cycle (not done)

Question 1

What is mitosis for?

Answer 1

needed for growth and repair
needed for asexual reproduction

Question 2

Describe the cell cycle:

Answer 2

• Interphase:
• G1: cell grows and new organelles and proteins are made
• S: DNA synthesis occurs (cell replicates its DNA)
• G2: cell produces more organelles and proteins
• Mitosis:
• prophase
• metaphase
• anaphase
• telophase
• Cytokinesis:
• the cytoplasm divides
• in animals, a cleavage furrow forms and the cells are pinched apart into two
• in plants, vesicles move to the equator to form two membranes called a cell plate. a new cell wall is laid down between the membranes

Question 3

Describe interphase in detail:

Answer 3

• DNA is unravelled and replicated
• organelles are replicated
• ATP content increases to provide energy for cell division

Question 4

Describe mitosis in detail:

Answer 4

• prophase:
• chromosomes condense and are visible as pairs of sister chromatids, joined at the centromere
• centrioles move to the opposite poles of the cell
• nucleolus disappears
• metaphase:
• nuclear envelope disappears
• chromosomes line up in the middle of the cell
• chromosomes are attached to the centrioles by spindle fibres
• anaphase:
• the centromeres divide, separating the sister chromatids
• the spindle fibres contract, pulling the chromatids toward the opposite poles of the cell, with the centromere going first
• telephase:
• the spindle fibres disperse
• the nuclear envelopes form and the chromosomes unravel
• the nucleoli form

Question 5

What is the mitotic index?

Answer 5

number of cells with visible chromosomes (undergoing mitosis)/total number of cells observed