1.6 Cell Division

Question 1

How do eukaryotic cells divide?

Answer 1

Mitosis. Create same DNA

Question 2

What is interphase?

Answer 2

An active period in the life of a cell when many metabolic reactions occur, including protein synthesis, DNA replication, and an increase in # of mitochondria and chloroplasts.

Question 3

What are the three stages of interphase?

Answer 3

G1: cell contents except DNA is duplicating as cell grows. S: DNA replication. G2: cell growth continues and DNA replication stops.

Question 4

What is mitosis?

Answer 4

The division of the nucleus into two genetically identical daughter nuclei. Growth, embryonic development, tissue repair and asexual reproduction involve mitosis.

Question 5

What are the four phases of mitosis?

Answer 5

Prophase, Metaphase, Anaphase, Telophase

Question 6

What happens in Prophase?

Answer 6

Chromatin supercoils to become chromosomes. Proteins called histones help w supercoiling. Nuclear mem. breaks down.

Question 7

What happens in Metaphase?

Answer 7

Microtubules grow and attach to centromeres of each double stranded chromosome. Chromosomes line in at equator (middle) of the cell.

Question 8

What happens in Anaphase?

Answer 8

Each centromere divides. Sister chromatids separate. Spindles pull single stranded chromosomes towards the two poles of the cell.

Question 9

What happens in Telophase?

Answer 9

Chromosomes pulled into tight group near MTOC (microtubule organizing centre). Nuclear membrane reforms. Chromosomes uncoil to form chromatin. Nucleolus forms. UNSEPARATED cell.

Question 10

What is cytokinesis?

Answer 10

Occurs after mitosis. Different in plant and animal cells. PHYSICAL CELL DIVISION.

Question 11

How does cytokinesis happen in plant cells?

Answer 11

Vesicles move to equator and fuse to form 2 layers of membrane. Cell plate forms in middle which becomes new cell wall in between daughter cells.

Question 12

How do prokaryotic cells divide

Answer 12

Binary fission. Create same DNA

Question 13

How does cytokinesis happen in animal cells?

Answer 13

Ring of contractile

Proteins pull inwards to form cleavage furrow. Squeezes centre of cell until two cell break apart from each other.

Question 14

What are cyclins and what do they do?

Answer 14

Proteins that endure tasks performed during cell cycle occur at the correct time and next phase occurs when it is supposed to. 4 types of cyclins, each must reach a threshold conc. before it triggers a specific task.

Question 15

How are tumours created?

Answer 15

Cell division that happens too quickly can cause tumours.

Question 16

What is a tumour?

Answer 16

Abnormal group of cells. Cells can stick together and do not travel or cells can detach and move elsewhere to develop into secondary tumours.

Question 17

What is a carcinogen?

Answer 17

Chemicals and agents that cause cancer. Chemical mutagens, high energy radiation, some viruses, etc.

Question 18

What is a mutagen?

Answer 18

Agents that cause gene mutation (random changes in the base sequence of DNA - changes order of A, T, C, G)

Question 19

What is a oncogene?

Answer 19

A gene that can become cancer-causing after mutation. Oncogenes involved in control of cell cycle so s mutation in onc. can cause uncontrolled cell division - tumour. Several mutations must occur in one cell for it to become a tumour cell.

Question 20

What is a mitotic index?

Answer 20

Important tool for predicting the response of cancer cells to chemo. The ratio between the # of cells in mitosis in a tissue and the total # of observed cells.

MI = mitosis/total cells