Cell Growth and Division

Cell Growth and Division

Cell division – when a cell produces two new daughter cells

Cell division is …the process that allows young organisms to growreplacement of injured and worn-out cellsor reproduction of single-celled organisms

Life Cycle of a Cell - Time Line

Interphase Mitosis

(most of the cells life) P M A T

Interphase

Inter – meaning betweenActive time between cell divisionsGrowing, making proteins or ATP, movingMost of the cells lifeAt the end DNA is copied exactly (duplicated) to prepare for mitosis

Nucleus

Cytoplasm

Cell membrane

Nucleolus

(ball of DNA)

Nuclear membrane

Mitosis

Cellular process of passing on DNADNA ( deoxyribonucleic acid) – code of cellular instructionsMitosis occurs in four stages: P – Prophase

M – MetaphaseA – Anaphase T - Telophase

Prophase

Pro – meaning beforeDNA forms strands called chromosomesCentrioles move to opposite sides of the nucleusNuclear membrane disappearsLong spindle fibers stretch between centriolesChromosomes attach to fibers

Cytoplasm

Cell membrane

Centriole

Spindle fibersChromosomes

Metaphase

Meta – meaning in the middleChromosomes line up in the middle of the cell

Cytoplasm

Cell membrane

Centriole

Spindle fibersChromosomes

Anaphase

Ana – meaning up or awayLooks like a tug-o-war of chromosomesDoubled chromosomes separateFibers shortenSingle chromosomes (chromatids) move to opposite sides

Cytoplasm

Cell membrane

Centriole

Spindle fibersChromatid

Telophase

Telo – meaning endChromosomes reach opposite ends of cellFibers disappearNuclear envelope forms around each new nucleusNew nuclei are identical to the parent nucleusCytoplasm and organelles move to either sideCytokinesis – cell pinches in half

Cell membrane

New nucleus

Nuclear envelope

Cytokinesis

Cytoplasm

Two New Daughter Cells !!!

Daughter cells are identical to their parent cells

Meiosis

Form of cell division that occurs in sex cells Creates sex cells called gametes

(sperm and eggs) Also known as reduction division During this process cells go through two divisions

which reduces the number of chromosomes to half (haploid)

Meiosis – Why reduce the number of chromosomes?

This is important because sperm and eggs combine during fertilization to form a zygote

The sperm and the eggs each contribute half the number of chromosomes to create a whole (diploid), if they were not half the new organism would have too many chromosomes.

(Mitosis)