Cell Division Cell Division Vocabulary Centriole Centromere Chromosome

Cell Division

Cell Division Vocabulary • • • Centriole Centromere Chromosome Chromatid Chromatin Cytokinesis • • • Diploid Gamete Haploid Meiosis Mitosis Somatic cells

• Centriole – Cell organelle that helps separate chromosomes during mitosis • Centromere – the “center” of a chromosome • Chromatid – One half of a chromosome • Chromatin – DNA in a loose, less condensed form • Cytokinesis • Chromosome – X-shaped structure made of condensed DNA – Division of cytoplasm

• Diploid – Cell having 2 copies of each chromosome – “ 2 n” • Gamete – Sex cell – Egg or sperm • Haploid – Cell having only one copy of each chromosome – “n” • Meiosis – Divides a diploid (2 n) cell into a haploid (n) cell – Necessary for sexual reproduction • Mitosis – Cell division • Somatic cells – Body cell (includes all but gametes)

Chromosomes

Eukaryotic Chromosomes

Eukaryotic Chromosome Structure • DNA typically exists in the form of chromatin but condenses into chromosomes during mitosis • To fit into chromosomes, DNA is wound around groups of proteins called nucleosomes • The nucleosomes are made of histone proteins

**Humans have 23 pairs (46 total) chromosomes in each autosomal cell**

Cell Cycle • Cells go through a predictable pattern of growth/development and replication • Interphase • Gap 1 • Synthesis • Gap 2 – Mitosis – Cytokinesis

Cell Growth and Division • Growth of an organism occurs due to the production of more cells, NOT because the cells get larger • Cell growth is limited by surface area to volume ratio – Cells can’t take in enough food or O 2 or get rid of waste

Rate of Cell Growth • Multicellular organisms have different types of tissues that grow and divide at different rates • If mitosis is not controlled, unlimited cell division occurs and can cause tumors – cancer

Interphase- G 1 Stage • 1 st growth stage after cell division • Cells mature by making more cytoplasm and organelles • Cell carries on its normal metabolic activities

Interphase- S Stage • Synthesis stage • DNA is copied (replicated)

Interphase- G 2 Stage • 2 nd growth stage • Occurs after DNA has been copied • All cell structures needed for division are made (ex: centrioles) • Both organelles and proteins are synthesized

Mitosis • Division of nucleus • Produces identical diploid (2 n) cells – Prophase – Metaphase – Anaphase – Telophase

Cytokinesis • Division of the cytoplasm

What Happens When Cells Can’t Stop Dividing? • Read this passage on cancer cells – Why is cancer cell division compared to “a car moving without having pressure applied to the gas pedal”? – What is the role of estrogen in a normal cell? – What is “contact inhibition”? Why is this important for normal cell growth? – Why do cancer cells often contain mutated DNA?