Chapter 9 - The Cell Cycle and Cellular Reproduction

cell cycle

differs in eukaryotes and prokaryotes

replication

interphase

longest phase. normal functions occur as well as preparation for cell division

G1

cell doubles it organelles

accumulates materials needed for DNA synthesis

S

DNA replication (synthesis)

chromosomes enter with 1 chromatid each and leave with 2 identical chromatids

G2

between DNA replication and the onset of mitosis

cell synthesizes proteins necessary for division

M

karokinesis

nuclear division

occurs in somatic cells (animals) and meristematic tissue (plants)

daughter chromosomes divide between the 2 daughter nuclei

4 phases

C

cytoplasmic division

results in 2 genetically identical diploid daughter cells

animals: cleavage furrow forms

plant: cell plate forms

chromosome

condensed rod-shaped DNA and protein molecules during cell division

chromatin

uncoiled chromosomes

tangles mass of threadlike DNA and protein in non dividing cell

chromatid

one of two identical strands into which a chromosome splits during mitosis

homologue

One member of a homologous pair of chromosomes

centromere

where the sister chromatids attach together

somatic cell

cell division increases, any of the cells of a plant or animal except the reproductive cells

mitosis

nuclear division in which chromosome number stays constant

DNA replication produces duplicated chromosomes

sister chromatids are genetically identical

centromere divides and each chromatid becomes a daughter chromosome

prophase

nuclear envelope breaks down

nucleolus disappears

chromatin condenses

spindle forms

metaphase

chromosomes align along the metaphase plate

chromosomes are pulled toward spindle fibers

anaphase

centromeres split

sister chromatids separate (daughter chromosomes)

pulled toward opposite pulls

cytokinesis beings

telophase

spindle disappears

2 daughter chromosomes

nuclear envelope starts to form

chromosomes become chromatin

nucleolus reappears

cytokinesis

division of cytoplasm

divides mother cells cytoplasm equally to daughter nuclei

enclosed each in its own plasma membrane

often begins in anaphase

clevage furrow

forms in animals to seperate the 2 cells in cytokinesis. formed by contractile ring of actin filaments

cell plate

forms in plants to seperate the 2 cells in cytokinesis

diploid

each chromosome is represented twice in the body. 23 diploid cells = 46 chromosomes

binary fission

asexual reproduction. the cell elongates and splits into two identical daughter cells

phases of eukaryotic cell cycle

important for growth, development and repair

interphase: G1, S, G2

mitosis: prophase, prometaphase, metaphase, anaphase, telophase

cytokinesis

what ways is the cell cycle controlled

External signals: Growth factors, Received at the plasma membrane, Cause completion of cell cycle

Internal signals: Family of proteins called cyclins, Must be present for stages to progress, Increase and decrease as cell cycle continues,

Without them cycle stops at G1, M or G2,

Allows time for any damage to be repaired

stages of mitosis

prophase, prometaphase, metaphase, anaphase, telophase

mitosis in plant cells

divide throughout their life. mitosis not necessary. do not have centrioles or asters. cell plate

mitosis in animal cells

cell division is necessary. mitosis necessary

significance of mitosis

permits growth and repair

cancer cells

can divide endlessly. unrestrained cell growth and division resulting in a tumor

undergo metastasis and angiogenesis

treatment for cancer

surgery, correct nutritional deficits, blood transfusion of RBC, gastric compression with GOO, radiation for palliative care

cell cycle in prokaryotic cell

asexual reproduction- binary fission

2 stages:

DNA is replicated

cell elongates then splits into two identical daughter cells