Topic E Cell Nuclear Division H2 2015

NANYANG JUNIOR COLLEGE H2 Biology Cell and Nuclear DivisionTopic E: Mitosis & Meiosis J1/20143 1 Formatted: Right: 0.01 cm TOPIC E: CELL & NUCLEAR DIVISION (MITOSIS & MEIOSIS) Learning Outcome Core Topic 1 – Cellular Functions Candidates should be able to: (l) Explain the importance of mitosis in growth, repair and asexual reproduction. (m) Explain the need for the production of genetically identical cells and fine control of replication. (n) Explain how uncontrolled cell growth can result in cancer, and identify causative factors (e.g. genetic, chemical carcinogens, radiation, loss of immunity) which can increase the chances of cancerous growth. (Knowledge that dysregulation of checkpoints of cell division can result in uncontrolled cell division and cancer is required, but detail of the mechanism is not required.) (o) Describe, with the aid of diagrams, the behaviour of chromosomes during the mitotic cell cycle and the associated behaviour of the nuclear envelope, cell membrane and centrioles. ( Names of the main stages are expected.) (p) Explain what is meant by homologous pairs of chromosomes. (q) Explain the need for reduction division (meiosis) prior to fertilisation in sexual reproduction. (p)(r) Explain how meiosis and random fertilisation can lead to variation. (s) Describe, with the aid of diagrams, the behaviour of chromosomes during meiosis, and t he associated behaviour of the nuclear envelope, cell membrane and centrioles. (N ames of the main stages are expected, but not the subdivisions of prophase.) Content Outline 1. The Role of Nucleus and Chromosomes in Cell Division (a) Chromatin Structure (b) Chromosome Structure (c) Chromosome Number (d) Homologous Chromosomes 1. 2. The Cell Cycle (a) Interphase (b) Mitosis (c) Cytokinesis (c)(d) Significance of Mitosis (e) Meiosis (d)(f) Significance of Meiosis (e)(g) Non-disjunction 3. Significance of Nuclear Division (a) Importance of mitosis (b) Importance of meiosis 4.3. The Control of Mitotic Cell Cycle Formatted: Font: Bold Formatted: English (Singapore) Formatted: Left, Indent: Left: 0 cm, Right: 0 cm, Space Before: 0 pt, After: 0 pt, Line spacing: single Formatted: Font: 10 pt Formatted: Font: 10 pt, Font color: Auto Formatted: Font: 10 pt Formatted: No bullets or numbering Formatted: Font: 10 pt, Font color: Auto Formatted: Numbered + Level: 1 + Numbering Style: a, b, c, … + Start at: 1 + Alignment: Left + Aligned at: 0.7 cm + Tab after: 1.4 cm + Indent at: 1.4 cm Formatted: Font: 10 pt

NANYANG JUNIOR COLLEGE H2 Biology Cell and Nuclear DivisionTopic E: Mitosis & Meiosis J1/20143 2 Formatted: Right: 0.01 cm (a) Genes involved in control of cell cycle (b) Onset of cancer (c) Causative factors References 1. Campbell, N. A. And Reece J.B. (201108) Biology. Chapter 12 :The Cell Cycle and Chapter 133: Meiosis and Sexual Life Cycles. 89th ed. Benjamin Cummings Publishing, Inc. 2. Clegg, C . J. And Mackean, D. J. (2000) A dvanced Biology, Principles and Applications. Chapter 9: The Nucleus in Divison and Interphase. 2nd ed. John Murray Publishing (Ltd) 3. Jones, M. And Jones, G . (2004) A dvanced Biology. Chapter 4 : Cell Division. Cambridge University Press. 1. The Role of Nucleus and Chromosomes in Cell Division All new cells are derived from pre -existing cells through cell division, a part of the cell cycle which includes: • Interphase - cell growth and synthesis of cell materials • Nuclear division - nucleus divides first to form two nuclei • Cytokinesis - cytoplasm divides to form two daughter cells The nucleus is responsible for carrying out cell division. (a) Chromatin Structure Chromatin is the complex of DNA and proteins: • is the complex of DNA and proteins. • It is the less condensed form of chromosome. present during interphase • Ddispersed as a mass of long, thin fibres when cell is not dividing and during interphase. • Two types of chromatin: Heterochromatin (highly condensed) and euchromatin (less condensed). • • The degreeLevel of condensation may change depending on circumstance: o Chromatin condenses by coiling to form chromosomes during cell division. o Chromatin decondenses for polymerases to gain access to specific regions of DNA for replication, gene expression or repair or gene expression. • Two types of chromatin: Heterochromatin (highly condensed) and euchromatin (less condensed). 10nm Formatted: Font: 10 pt Formatted: Font: 11 pt, Not Expanded by / Condensed by Formatted: Indent: Left: 0.7 cm, Line spacing: single, No bullets or numbering, Don't snap to grid Formatted: Font: 11 pt Formatted: Line spacing: single, Numbered + Level: 1 + Numbering Style: 1, 2, 3, … + Start at: 1 + Alignment: Left + Aligned at: 0 cm + Tab after: 0.7 cm + Indent at: 0.7 cm, Don't snap to grid Formatted: Line spacing: single, Don't snap to grid Formatted: Add space between paragraphs of the same style, Line spacing: single, Don't snap to grid Formatted: Line spacing: single, Don't snap to grid Formatted: Add space between paragraphs of the same style, Line spacing: single, Don't snap to grid Formatted: Indent: Left: 1.97 cm, Add space between paragraphs of the same style, Line spacing: single, No bullets or numbering, Don't snap to grid Formatted: Add space between paragraphs of the same style, Line spacing: single, Don't snap to grid Formatted: Font color: Auto Formatted: Indent: Left: 2.75 cm, No bullets or numbering Formatted: Font: Bold

NANYANG JUNIOR COLLEGE H2 Biology Cell and Nuclear DivisionTopic E: Mitosis & Meiosis J1/20143 3 Formatted: Right: 0.01 cm DNA packed into chromatin and chromosome Eukaryotic DNA contains millions of nucleotides. In humans, the DNA material in a cell has a total length of abou t 1.8m long! However, the radius of the nucleus is only about 6µm. Hence, each DNA molecule must be packed into a compact structure that is about 50,000 times shorter that its extended length. Condensation of chromatin into chromosome: • Negatively-charged double-helix DNA (2nm) is wound twice around histone proteins that have positively charged lysine and arginine residues to form a nucleosome. • Nucleosomes are joined by linker DNA, giving rise to ‘beads-on-a-string’ structure (10nm chromatin fibre). Formatted: Indent: Left: 0 cm Formatted: Font color: Auto Formatted: Indent: Left: 1.27 cm, First line: 0 cm, Line spacing: single Formatted: Font color: Auto Formatted: Font color: Auto Formatted: Font color: Auto, English (Singapore) Formatted: Line spacing: single Formatted: Font color: Auto Formatted: Indent: Left: 0.57 cm, Line spacing: single Formatted: Indent: Left: 1.37 cm, Add space between paragraphs of the same style, Line spacing: single Formatted: Font color: Auto Formatted: Font color: Auto

NANYANG JUNIOR COLLEGE H2 Biology Cell and Nuclear DivisionTopic E: Mitosis & Meiosis J1/20143 4 Formatted: Right: 0.01 cm DNA wound around histone proteins • Nucleosomes and linker DNA are coiled into a solenoid structure , forming a 30nm chromatin fibre. • 30nm chromatin fibres are folded into looped domains that are attached to non- histone scaffolding proteins, forming 300nm chromatin fibres. • 300nm chromatin fibres are further folded to form 700nm chromatin fibres found on one of the sister chromatids on a duplicated chromosome. 10nm Formatted: Font: Bold, Font color: Auto Formatted: Add space between paragraphs of the same style, Line spacing: single Formatted: Font color: Auto Formatted: Font color: Auto

NANYANG JUNIOR COLLEGE H2 Biology Cell and Nuclear DivisionTopic E: Mitosis & Meiosis J1/20143 5 Formatted: Right: 0.01 cm (b) Chromosome Structure During cell division, chromatin condenses into chromosomes, which may exist as unduplicated chromosomes or duplicated chromosomes. Diagram showing duplicated chromosome and undup