Continuity of Cells Flashcards
What does Mitosis do?
Ensures the daughter cells produced during cell division have exactly the same chromosome makeup as the parent cell.
What is Mitosis?
The division of the chromosomes.
What is Cytokinesis?
The division of the cell into two daughter cells.
What order is the cell cycle?
G1 phase, S phase, G2 phase, Mitosis and Cytokinesis.
How is the cell cycle controlled?
Multiple checkpoints that monitor that the previous stages have been carried out correctly.
What does the G1 checkpoint ensure?
The cell has reached critical size, there are enough nutrients available for the next stages, there is no DNA damage.
When does and what happens during the G2 checkpoint?
At the end of the G2 phase, ensure DNA replication has taken place accurately and that there is no DNA damage. If there are no problems, mitosis will begin.
How is cancer caused?
Uncontrolled cell division, cancer cells break down the ability of checkpoints to regulate the cell cycle.
How do anti-cancer drugs work?
Disrupting the cell cycle and stopping the process of mitosis, this use of drugs is called chemotherapy.
What does DNA do in the S phase to prepare for mitosis?
The DNA doubles during the S phase.
What do DNA consist of?
An extended DNA molecule supported by histones. Histones are folded into compact stacks and the DNA coils tightly around the stack to form a nucleosome.
What does diploid mean?
A cell or nucleus consisting of two pairs of homologous (the same) chromosomes.
How many chromosomes do humans have?
46
What are the four stages of Mitosis?
Prophase, Metaphase, Anaphase and Telophase.
What happens during Prophase?
Chromatin in the nucleus becomes condensed. Nucleolus disappears, centrioles move towards opposite ends. Centrioles are involved in the formation of the spindle. By late prophase the centrioles would have completed migration and spindle will have formed. The nuclear membrane will have broken down and each chromosome can be seen to consist of two chromatids joined by a centromere.
What happens during Metaphase?
Chromosomes are aligned along the ‘equator’ of the cell, the spindle fibres attach to the centromeres.
What happens during Anaphase?
The centromeres attaching the two chromatids of each chromosome split and the contraction of the spindle fibres pulls the chromatids apart, as Anaphase continues chromosomes are pulled further apart to the opposite ends of the cell.
What happens during Telophase?
Sister chromatids end up at opposite poles of the cell and are usually referred to as chromosomes. The chromosomes decondense and become less visible, the nucleolus reappears, the nuclear membrane reforms and spindle fibres disappear.
What happens during Cytokinesis?
The cell divides during Cytokinesis to form two daughter cells, each with identical chromosome makeup.
What happens during Cytokinesis in animal cells?
In animal cells a cleavage furrow forms as the cell surface membrane invaginates and splits the cell into two.
What happens during cytokinesis in plant cells?
A cell plate precursor to a new cell wall is laid down.
What is the definition of Mitosis?
The process of nuclear division, a necessary prerequisite for cell division. Important in growth and tissue repair.
