Mitosis: Cell Division

Terminology• DNA – made of nucleic acids, housed in the

nucleus, contains genes

• Chromatin – long strands of DNA that are wrapped around proteins (histones)

• Nucleosome – the DNA/ histone complex

Why does mitosis happen?

• Surface area to volume ratio– As a cell grows, the volume grows faster than

the surface area– Not enough space in the cell membrane to send

wastes out or to bring food in

• Signal is sent to the cell– An organism needs to grow– To repair damage

Structure of a Chromosome•Chromosome – a structure that is made of DNA and the proteins associated with it

•Chromatid – one of the 2 exact copies of the DNA – often referred to as “sister chromatids” – the 2 of them together make a chromosome

•Centromere – the point where the 2 chromatids are connected together to make a chromosome

Homologous Chromosomes

•two chromosomes that code for the same traits. One is from mom the other is from dad

Cell Cycle• Interphase

– Majority of a cell’s life– Cell grows– Chromosomes duplicate

• Mitosis– Creates 2 daughter cells

that are identical to the parent cell

– Cell division

Interphase

• G1– Growth One– The cell spends most of its life

• S – Chromosomes are duplicated

• G2– Organelles and other parts needed for cell

division are duplicated

Mitosis

• Prophase – the chromosomes become visible – the nuclear envelope disappears – pro = first

• Metaphase – the chromosomes line up in the middle of the cell

• Anaphase – the sister chromatids move away from each other

• Telophase – begins as chromatids reach opposite ends of the cell

Cytokinesis

• The cytoplasm and organelles are divided between the two sides

• Plants: – A cell plate begins forming

• Animals:– A cleavage furrow forms as the

cell pinches inward

Levels of Organization

O rg a n ism

O rg an S yste m s

O rg a ns

T issu e s

C e lls

When Good Cells Go Bad!

• Who will develop it? – ½ of men and 1/3 of women in the U.S. will

develop cancer in their lifetime

• What is it? – Uncontrolled cell division

• What causes the cell to keep dividing? – Failure to produce internal regulators or respond

to external regulators

Facts about cancer

Causes of Cancer• a.   Tobacco use – lung, mouth, esophageal,

cervical cancer• b.  Asbestos – lung cancer• c.   Radiation exposure• d.  Viral infection - HPV• e.   Charred meat – colon cancer• f.     Genetic• g.   Chemical exposure• h.  UV exposure (sun or tanning bed) – skin

cancer• i. Drinking more than one drink a day for women

or 2 a day for men

Kinds of Cancer• Metastatic

– More dangerous– Cancer travels in the

body

• Nonmetastatic– Usually less dangerous– Cancer does not travel

Not all cancers form tumors and not all tumors are cancerous!

How does cancer spread?

Pancreatic Cancer