1.6 Cell division

Question 1

Phases of cell division

Answer 1

1. Interphase
2. Prophase

Metaphase

Aanaphase

Telophase

3. Cytokinesis

Question 2

Interphase

Answer 2

Interphase: growth and production of organelles (the longest phase)

DNA replication - protein synthesis, number of organeeles increase

G1: growth, metabolism, contents duplicated (except chromosomes)

S: DNA replication - chromosomes duplicated

G2: growth, DNA checked for mutations, metabolism begins

Question 3

Define mitosis

Answer 3

MITOSIS: division of the nucleus

Question 4

Define cytokinesis

Answer 4

CYTOKINESIS: division of the cell

Question 5

Cytokinesis

Answer 5

CYTOKINESIS: occurs after mitosis - different in animals/plants

ANIMALS: membrane pulled inwards - cleavage furrow - accomplished by contractile proteins (actin, myosin) at the equator - pinches apart -> two cells

PLANTS: vesicles are moved to equator - fuse - form tubular structure - form two membranes - petins brought in by vesicles are deposited by exocytosis - lamella - bring cellulose - new cell wall

Question 6

Mitosis

Answer 6

MITOSIS: asexual reproduction, growth, repair, cloning

P - chromosomes supercoil
M - microtubules grow, nuclear envelop breaks down, line at equator
A - spindle fibres contract and pull chromatids apart
T - chromatids in poles, nuclear envelope reforms, spindle disappears

Question 7

Cyclins

Answer 7

CYCLINS: group of proteins involved in control of the cell cycle (division)

Cyclins bind to enzyme-depedent kinases - active - attach phosphate to cell proteins - activates other proteins - procede in mitosis

Question 8

Mitotic index

Answer 8

MITOTIC INDEX: shows the ration between cells in mitosis and total number of cells

Can be used to determine tumor development

Question 9

Tumor

Answer 9

TUMOR: abnormal group of cells which are cancerous

BENIGN: not harmful, don’t invade other tissues

MALIGNANT: life threatening, spread to other tissues/organs - secondary tumors

Question 10

Cancer

Answer 10

CANCER: disease caused by malignant tumors

CAUSES: carcinogens (chemicals, agents, viruses), mutagens (cause genetic mutations: chemicals, high E radiation - x-rays, UV)

Question 11

Cancer mutations

Answer 11

ONCOGENS: genes that can become cancer-causing after mutating, usually invovled in control of cell cycle, division -> results in uncontrolled cell division (tumor)

Question 12

Smoking and cancer

Answer 12

SMOKING: positive correlation between number of cigarettes and cancer cases (affects lungs, esophagus, stomach, kidney, bladder, pancreas) - carcinogens in smoke