Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Past paper question – Jan 11 Qu 1 Stem Cells Settler • Compare mitosis and meiosis Cell division division of the nucleus and then the cell • Mitosis • Meiosis • For Growth • Produces 2 identical daughter nuclei • Same number of chromosomes to parent cell • No variation • For gamete production • Produces 4 different daughter nuclei • Different number of chromosomes to parent cell • Causes Variation Starter • Define these words: 1) Gene 2) Locus 3) Allele 4) Mitosis 5) Meiosis 6) Homologous chromosomes 7) Chromatid 8) Diploid A. One of the two copies of a chromosome that are joined together by a centromere prior to cell division B. A type of cell division where the chromosome number is halved C. One of the different forms of a particular gene D. A section of DNA that codes for a polypeptide E. A type of cell division where the daughter cells have the same number of chromosomes as the parent cell F. A term referring to a nucleus which contains two pairs of chromosomes. G. A pair of chromosomes (one maternal and one paternal) that have the same gene loci. H. The position of a gene on a chromosome Starter • • • • • • • Define these words: Gene Locus Allele Mitosis Meiosis Homologous chromosomes • Chromatid • Diploid A. One of the two copies of a chromosome that are joined together by a centromere prior to cell division B. A type of cell division where the chromosome number is halved C. One of the different forms of a particular gene D. A section of DNA that codes for a polypeptide E. A type of cell division where the daughter cells have the same number of chromosomes as the parent cell F. A term referring to a nucleus which contains two pairs of chromosomes. G. A pair of chromosomes (one maternal and one paternal) that have the same gene loci. H. The position of a gene on a chromosome Stem Cells Learning Objectives • Understand and give examples of how stem cells can be modified for use in medicine • Produce a written summary for and against stem cell research Success Criteria • Define the term ‘stem cell’ (Grade D-E) • Explain the meaning of the term homologous pair of chromosomes(Grade C) • Outline the process of cell division by budding in yeast (Grade C) • Construct diagrams to describe the stages of mitosis (Grade A-B) Specialized cells In a single-celled organism, all the functions necessary for life must be carried out in one cell. In contrast, multicellular organisms can delegate jobs to particular groups of cells. Cells that have adapted to a specific function are known as specialized cells. Specialized cells are grouped into tissues, which combine to make organs and organ systems. Tissues, organs and organ systems Cells, tissues and organs must cooperate with each other – different ways of communication – transport systems and communication systems Plant structure Students should be aware of the differences between squamous and ciliated epithelia, xylem and phloem Stem cells Adult stem cells in the bone marrow can divide and differentiate to replace worn out blood cells – erythrocytes (red blood cells) and neutrophils (white blood cells) Plants • Plants are always growing , stem cells can differentiate into various plant tissues • Example - Stem cells are found in the cambium. The vascular cambium forms a ring inside the shoot and root, the cells divide and grow out from the ring differentiating as they move away, to form the xylem and phloem. Specialised cells - on whiteboards how are each adapted for their function (in pairs and share) 1. erythrocytes, 2. neutrophils, 3. epithelial cells, 4. sperm cells and 5. palisade mesophyll cells, 6. root hair cells , 7. guard cells Rest phase Cells often stop dividing once they are fully differentiated, so where do they fit into the cell cycle? Specialized cells move from G1 into a resting phase known as G0. A cell may remain in G0 for the rest of its lifetime, or it may just rest in this state temporarily. G0 G0 is also the phase in which stem cells wait until their associated body cells need replacing. Task - Stem cells - Using current newspaper articles have students produce summaries, for and against stem cell research Cell differentiation Chromosome number A human somatic (body) cell contains 46 chromosomes. These consist of 23 pairs of homologous chromosomes. Each pair contains one chromosome from each parent. Other species have different numbers of these homologous pairs. Sex cells, or gametes, have only one copy of each chromosome: they are haploid. A somatic cell, containing two of each, is called diploid. Haploid gametes All somatic cells in a multicellular organism are genetically identical because they are the result of mitosis. They are all descended from a single cell – a zygote. A zygote is formed when two haploid gametes fuse. These gametes are genetically unique because, unlike somatic cells, they were formed by a special form of cell division called meiosis. Meiosis I and II Meiosis is the process of cell division underlying sexual reproduction. It is a two-stage process: Meiosis I introduces genetic diversity by randomly dividing a cell’s genes in two. It results in two haploid cells. Meiosis II is similar to mitosis. It splits each chromosome into its two chromatids and places one in each daughter cell. It results in four haploid gametes. Genetic variation Sexual reproduction creates genetic diversity within a population, which is vital to a species’ survival. Two processes during meiosis determine the unique genetic makeup of the four daughter cells: During meiosis I, homologous pairs of chromosomes swap parts of their genetic material. This is crossing over. The chromosomes from each pair are randomly allotted to the daughter cells by independent assortment. Meiosis: true or false? Variation from meiosis Task 1) Look at the diagram to describe the process of budding in yeast cells http://www.microbiologybytes.com/video/Sc erevisiae.html 2) Using page 32 draw a table to compare natural an artificial clones 3) Answer questions page 33