RVHS 12. The Cell Cycle 9477

River Valley High School 2025 JC1 H2 Biology Lecture Topic 12: The Cell Cycle 1 River Valley High School 2025 JC1 H2 Biology Lecture Topic 12: The Cell Cycle Name: ( ) Class: 25J____ Date: References Title Author Biology (9th edition) Campbell and Reece Biological Science 2: Systems, Maintenance & Change (3rd edition) Taylor, Green and Stout AS Level Biology Bradfield, Dodds and Taylor Molecular Biology of the Cell (5th edition) Alberts, Johnson, Lewis, Raff, Roberts and Walter Websites URL Description Chromosome numbers during cell division How to distinguish chromosomes numbers throughout replication, mitosis and meiosis Mitosis Clear, colourful and narrated 2D animations on mitosis Cell cycle and cancer How dysregulation of cell cycle checkpoints can lead to cancer Meiosis Clear, colourful and narrated 2D animations on meiosis Mitosis and Meiosis - comparison A comparison between mitosis and meiosis Role of RAS protein in Cancer development How RAS protein affects cancer development Role of p53 in cancer How p53 protein affects cancer development Why is it so hard to cure cancer? The complications of cancer

River Valley High School 2025 JC1 H2 Biology Lecture Topic 12: The Cell Cycle 2 H2 Biology Syllabus 9477 (2025) Candidates should be able to use the knowledge gained in the following section(s) in new situations or to solve related problems. Related Topics Content DNA Replication DNA structure and function Inheritance The passage of information from parent to offspring Linkage and crossing-over Learning Outcomes 2E: The Cell Cycle a. Describe the events that occur during the mitotic cell cycle and the main stages of mitosis (including the behaviour of chromosomes, nuclear envelope, cell surface membrane and centrioles). b. Explain the significance of the mitotic cell cycle (including growth, repair and asexual reproduction) and the need to regulate it tightly. (Knowledge that dysregulation of checkpoints of cell division can result in uncontrolled cell division & cancer is required, but detail of the mechanism is not required). c. Identify the causative factors, including genetic, chemical carcinogens, ionising radiation and loss of immunity, which may increase the chances of cancerous growth. d. Explain how the loss of function mutation of tumour suppressor genes, including p53, and gain in function mutation of proto-oncogenes, including ras, results in uncontrolled cell division. e. Describe the development of cancer as a multi -step process that includes accumulation of mutations, angiogenesis and metastasis. f. Describe the events that occur during the meiotic cell cycle and the main stages of meiosis (including the behaviour of chromosomes, nuclear envelope, c ell surface membrane and centrioles) (names of the main stages are expected, but not the sub-divisions of prophase). g. Explain the significance of the meiotic cell cycle (including how meiosis and random fertilisation can lead to variation). Lecture Outline I. Introduction A. Cell division & continuity of life B. Chromosomes C. Mitotic / Meiotic Spindle II. The Cell Cycle A. Phases of the Cell Cycle B. Control of the Cell Cycle C. Detailed Events of Interphase D. Detailed Events of Mitotic Phase E. Significance of Mitosis III. Cancer A. Cancer is a Genetic Disease B. Cancer is a Multistep Process C. The Progression of Cancer IV. Meiosis A. Stages of Meiosis: Meiosis I and II B. Significance of Meiosis C. Comparison of Mitosis and Meiosis

River Valley High School 2025 JC1 H2 Biology Lecture Topic 12: The Cell Cycle 3 I. INTRODUCTION A. Cell Division and the Continuity of Life The ability of organisms to reproduce is one characteristic that distinguishes them from non -living matter. This unique capacity to procreate has a cellular basis. As modern cell theory states, the only way to make a new cell is to duplicate a cell that already exists. This would imply that all living organisms, unicellular or multicellular, are products of repeated rounds of cell growth and division extending back in time to the beginnings of life on Earth. A cell reproduces by performing an orderly sequence of events in which it duplicates its contents and then divides in two . This cycle of duplication and division , known as the cell cycle , is the essential mechanism by which all living things reproduce. While the details of the cell cycle vary across organisms, certain characteristics are universal: ⬧ The most fundamental task of the cell cycle is to allow the cell to pass on its genetic information accurately to the next generation of cells. ⬧ To produce two genetically identical cells, the DNA in each chromosome must first be faithfully replicated to produce two complete copies, and the replicated chromosomes must then be accurately distributed to the two daughter cells , so that each receives a copy of the entire genome . B. Chromosomes Chromosome numbers and sets ⬧ Every eukaryotic species has a characteristic number of chromosomes in each cell nucleus. The following table illustrates several examples: Common name Species name Chromosome number (in somatic cells) Human Homo sapiens 46 Monkey Macaca mulatta 42 Mouse Mus musculus 40 Mosquito Aedes aegypti 6 Fruit Fly Drosophila melanogaster 8 Flatworm Planaria torva 16 Corn Zea mays 20 Yeast S. cerevisiae 32

River Valley High School 2025 JC1 H2 Biology Lecture Topic 12: The Cell Cycle 4 Karyotype of a human male (with a normal 46, XY constitution). Homologous pairs of non-sex chromosomes (autosomes) are numbered from 1 to 22. There is 1 pair of sex chromosomes (X and Y). ⬧ In particular, the nuclei of human somatic cells each contain 46 chromosomes. o If all the 46 chromosomes are lined up according to size it can be seen that there are in fact 23 distinct pairs of chromosomes. o The 23 pairs of chromosomes comprise 22 pairs of autosomes (non-sex chromosomes) and one pair of sex chromosomes, which determines the gender of the organism. o Each pair is known as a homologous pair of chromosomes , with each member of a pair called a homologue. o The 46 chromosomes are said to be made up of two sets of 23 chromosomes. o Each set of chromosomes is inherited from one parent . Hence, one set is called the maternal set and the other is called the paternal set.

River Valley High School 2025 JC1 H2 Biology Lecture Topic 12: The Cell Cycle 5 Haploid versus diploid ⬧ Cells or organisms with two sets of chromosomes (i.e. contain both chromosomes from each homologous pair) are referred to as diploid, and given the symbol 2n. ⬧ Cells or organisms with only one set of chromosomes (i.e. contain only one chromosome from each homologous pair) are referred to as haploid, and given the symbol n. ⬧ Gametes, or sex cells, are haploid cells. ⬧ Fusion of two haploid gametes (sperm and ovum) during fertilisation restores the diploid condition , giving rise to a zygote (2n). ⬧ By the process of cell division involving mitosis, the zygote (2n) then divides to give rise to a mature organism with cells of the same genetic makeup (2 n), thus conserving the number of chromosomes across generations of cells. ⬧ Haploid gametes ( n) are in turn produced via meiosis, whereby diploid parent cells (2 n) divide to give rise to cells with half the number of chromosome Chromosomes and Chromatids ⬧ Definition of chromosome: A cellular structure carrying genetic material, found in the nucleus of eukaryotic cells. Each chro