the cell cycle - mcccblinderl/documents/thecellcyclech12_postpdf.pdf · have 1 set = haploid...

C H A P T E R 1 2

The Cell Cycle

The Key Roles of Cell Division

cell division = reproduction of cells

All cells come from pre-exisiting cells

Omnis cellula e cellula

Unicellular organisms division of 1 cell reproduces organism

Binary fission

Why cells reproduce Development/Growth

Replacement

Repair

Multicellular organisms

100 µm 200 µm 20 µm

(a) Reproduction (b) Growth and development

(c) Tissue renewal

Cellular Organization of Genetic Material

chromosome = strand of DNA

2 sets of 23 chromosomes in humans = 46

genome = All DNA in a cell

20 µm

chromatin complex of DNA and protein

Somatic cells= body cells (2 trillion in adult)

two sets of chromosomes (pairs= diploid)

Produced by mitosis - 1 diploid cell 2 identical diploid cells

Gametes sperm and eggs have 1 set = haploid

Produced by meiosis– 1 diploid cell 4 unique cells

Occurs only in ?

Gametes

Identical cells Unique cells

Diploid Haploid

Concept check

1. start with a fertilized egg 5 cell divisions produce how an embryo of ______ cells

2. a chicken has 78 chromosomes in a somatic cell. How many chromosomes in a chicken sperm?

Human Arabidposis

The cell cycle = time from new cell to when it divides

Interphase – 90% of time

Mitosis 4o min

S (DNA synthesis)

G1

G2

Cell Division

Mitosis = division of the nucleus

Cytokinesis = division of cytoplasm

INTERPHASE

G1 phase – cell grows, gets ready

S phase – DNA replicates

G2 phase – cell grows, gets ready

S (DNA synthesis)

G1

G2

If cycle is 24

hrs, how long

each phase?

Signs of interphase?

S phase of Interphase

Chromosomes (DNA) replicate

Sister chromatids = 2

Centromere = constricted region

0.5 µm Chromosomes

Chromosome duplication (including DNA synthesis)

Chromosome arm

Centromere

Sister chromatids

DNA molecules

Separation of sister chromatids

Centromere

Sister chromatids

Prophase

Prometaphase

Metaphase

Anaphase

Telophase

Cytokinesis by late telophase

MITOSIS video

Chromosomes condense

Mitotic spindle forms from centrioles

Nuclear membrane breaks apart

I. Prophase

The mitotic spindle (formation begins in prophase)

Prophase G2 of Interphase

Aster Centrosomes

Aster = radial array of microtubules

Prophase

II. Metaphase

chromosomes (sister chromatids) line up at the metaphase plate

midway between spindle’s two poles

Microtubules Chromosomes

Sister chromatids

Aster

Metaphase plate

Centrosome

Kineto- chores

Kinetochore microtubules

Overlapping nonkinetochore microtubules

Centrosome 1 µm

0.5 µm

Prophase Prometaphase G2 of Interphase

Prometaphase Prophase G2 of Interphase

Nonkinetochore microtubules

Fragments of nuclear envelope

Aster Centromere Early mitotic spindle

Chromatin (duplicated)

Centrosomes (with centriole pairs)

Nucleolus Nuclear envelope

Plasma membrane

Chromosome, consisting of two sister chromatids

Kinetochore Kinetochore microtubule

Metaphase Anaphase Telophase and Cytokinesis

Metaphase Anaphase Telophase and Cytokinesis

Cleavage

furrow

Nucleolus

forming

Metaphase

plate

Centrosome at

one spindle pole Spindle

Daughter

chromosomes Nuclear

envelope

forming

III. Anaphase

sister chromatids separate

microtubules shorten – depolymerize to move chromosomes toward opposite ends of cell

IV. Telophase

Identical nuclei form at opposite ends of cell

Chromosomes less condensed

Cytokinesis

Division of cytoplasm

animal cells cleavage furrow

plant cells cell plate

Text animation mitosis and cytokinesis

Bioflix animation

Animal mitosis time lapse

Cleavage furrow

100 µm

Daughter cells

(a) Cleavage of an animal cell (SEM)

Contractile ring of microfilaments

Daughter cells

(b) Cell plate formation in a plant cell (TEM)

Vesicles forming cell plate

Wall of parent cell

New cell wall Cell plate

1 µm

Nucleus

Prophase 1

Nucleolus

Chromatin

condensing

Prometaphase 2

Chromosomes

Metaphase 3

Anaphase 4

Telophase 5

Cell plate 10 µm

Text animation mitosis and

cytokinesis

Bioflix animation

Animal mitosis time lapse

S G1

M checkpoint

G2 M

Control system

G1 checkpoint

G2 checkpoint

Cancer cells lose control of the cell cycle

Lose contact inhibition

Lose anchorage dependence

Cells normally attached to a substrate in order to divide

Breast cancer cells dividing

Contact inhibtion

Anchorage dependance

Cancer cells

May not need growth factors

May make own growth factor

Transformed Immortal

Abnormal chromosomes

Cancer cells

necrotic

Mucus lake

Abnormal

nucleus

Lung cancer

Tumor mass of abnormal cells

Benign tumor – abnormal cells do not invade other tissues

Malignant tumors - invasive

can metastasize and form secondary tumors

Angiogenesis - tumor gets a blood supply

Metastasis – tumor spreads to other locations

Tumor

A tumor grows

from a single

cancer cell.

Glandular tissue

Lymph vessel

Blood vessel

Metastatic tumor

Cancer cell

Cancer cells

invade neigh-

boring tissue.

Cancer cells spread to other parts of the body.

Cancer cells may survive and

establish a new

tumor in another

part of the body.

1 2 3 4

Treatments

Radiation destroys fast growing cells (target site)

Chemotherapy

Excision