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CHROMOSOMES AND CELL REPRODUCTION

CHROMOSOMES AND CELL REPRODUCTION. Section I Chromosomes Formation of New Cells by Cell Division. New cells are formed when old cells divide. 1. Cell division is the same as cell reproduction. 2. The type of cell division differs depending on the organism.

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CHROMOSOMES AND CELL REPRODUCTION

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  1. CHROMOSOMES AND CELL REPRODUCTION

  2. Section I ChromosomesFormation of New Cells by Cell Division . • New cells are formed when old cells divide. • 1. Cell division is the same as cell reproduction. • 2. The type of cell division differs depending on the organism.

  3. Prokaryotic cells, likeBacteriareproduce by binary fission. • Binary fission: asexual/ a single parent passes exact copies of its DNA to its offspring • 1st stage: DNA is copied • 2nd stage: Cell divides

  4. Eukaryotic cells reproduce byanother type of cell division-MITOSIS • 1st stage: DNA is copied • chromatids: 2 exact copies of DNA that make up a chromosome • centromere: point of attachment of 2 chromatids • 2nd Stage: DNA and protein coil into chromosomes

  5. Draw and Label a chromosome:

  6. The chromatids separate during cell division and are each placed into a new cell. This ensures that each cell has the same genetic information as the original cell. • When a cell divides: the DNA is copied 1st and then distributed. Each cell ends up with a complete set of the DNA.

  7. Gamete cells- which are sperm and egg are created through another type of cell division-MEIOSIS Egg cell surrounded by sperm cells.

  8. II. Chromosome Number and Structure Humans have 46 chromosomes (23 Pairs) in somatic cells. Somatic cells: All body cells (except sex cells) Gametes: sex cells (sperm and eggs) Chromosomes differ in size, shape and set of genes.

  9. Sets of Chromosomes • Homologous chromosomes are those that are paired together and are similar in size, shape and genetic content. • 46 chromosomes = 2 sets of 23

  10. Diploid- cell contains 2 sets of chromosomes Haploid- cell contains 1 set of chromosomes The fusion of 2 haploid cells forms a diploid zygote. Zygote-fertilized egg cell

  11. B. Sex Chromosomes • Out of 23 pairs of chromosomes- 22 pairs are autosomes; 1 pair are sex chromosomes. • Sex chromosomes are the X and Y. • Male Sperm determines the sex of a child. • XX = Female XY = Male

  12. C. Change in Chromosome Number • There are 1000’s of genes on each of our chromosomes. • The presence of all 46 chromosomes is essential for normal development and function. • Trisomy- having an extra copy of a chromosome • Example: Trisomy 21- Down’s Syndrome • Cause of Trisomy is NONDISJUNCTION. • This is when the chromosomes don’t separate and one gamete ends up with 2 chromosomes.

  13. Mikey has Down’s Syndrome.He has an extra chromosome. Instead of having a pair of # 21 chromosomes, he as 3 copies of it.

  14. Karyotype: Normal vs Down’s Syndrome

  15. D. Change in Chromosome Structure- MUTATIONS • Types of Mutations: 1. Deletion- piece of chromosome breaks off 2. Duplication- extra chromosome fragment attaches; 2 copies of certain genes 3. Inversion-chromosome attaches in reverse order 4. Translocation – chromosome piece attaches to a nonhomologous chromosome

  16. Draw these Chromosomal Mutations

  17. Jacobsen syndrome: report of a patient with severe eye anomalies, growth hormone deficiency, and hypothyroidism associated with deletion 11

  18. Section II- The Cell CycleA. Cell cycle-Cellular growth and division • 90%of the time is spent inInterphase. (preparation to divide) • The cell will enter the last 2 phases of the cell cycle only if it is about to divide.

  19. 5 Phases of the Cell CycleThe 1st 3 stages are part of Interphase. • 1. 1st Growth (G1)-Grows rapidly (nerve cells stay in this stage) • 2. Synthesis- DNA is copied; each chromosome is copied • 3. 2nd Growth (G2)- Growth; prep for division; microtubules are assembled • 4. Mitosis- nucleus divides into 2 nuclei (2 cells) that are identical • 5. Cytokinesis- cytoplasm divides

  20. Mitosis and cytokinesis produce new cells that are identical to the original cells and allow organisms to grow, replace damaged tissue, and in some organisms, reproduce.

  21. B. How do cells “know” when to divide? “Red light- Green light” • The cell cycle in eukaryotes is controlled by many proteins. • 1.Cell growth check point(G1): makes decision whether cell will divide • 2. DNA synthesis checkpoint(G2): protein triggers mitosis and cell begins many processes needed to proceed into mitosis • 3. Mitosis checkpoint: triggers the exit from mitosis; It signals the beginning of G1.

  22. G1 Checkpoint – proteins make sure enough growth has occurred • Synthesis Phase • “S” phase • Duplication, Replication, “copying” chromosomes Growth Phase 1 First Growth Phase G1 - Grows, grows Interphase – The first 3 phases of the cell cycle Growth Phase 2 Second Growth Phase G2 - Grows, centrioles double, start moving to opposite poles, microtubules form Mitosis Dividing of the nucleus – 2 nucli Cytokinesis -cytoplasm divides completely 2 new cells G2 Checkpoint – proteins make sure enough growth has occurred and chromosomes have replicated completely Telophase Mitosis Checkpoint – proteins check to make sure divisions has completed. Anaphase Prophase Metaphase

  23. CANCER- • Uncontrolled growth of cells • It is essentially a disorder of cell division. • Cancer cells do not respond normally to the body’s control mechanisms • Some Mutations cause cancer by over-producing growth-promoting molecules, thus speeding up the cell cycle or by inactivating the control proteins that normally act to slow or stop the cell cycle.

  24. Section III Mitosis and Cytokinesis • 4 stages of Mitosis: 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase

  25. Chromosomes become visible, the nuclear envelope dissolves and the spindle forms. What makes up the spindles? It is made up of centrioles & individual microtubule fibers; they are involved in moving the chromosomes. Prophase:

  26. Metaphase • Chromosomes line up in the Middle (middle phase)

  27. Anaphase • Centromeres divide, chromatids move toward opposite poles.

  28. Telophase • Nuclear envelope reforms at each pole, chromosomes uncoil , spindle divides. • Mitosis is complete and cytokinesis begins.

  29. Cytokinesis • Cytoplasm divides in half, and the membrane grows to enclose each cell, 2 separate cells are formed.

  30. A Difference in Plant Cells • A cell plate forms across the middle of the plant cell. A new cell wall forms on both sides of the cell plate.

  31. Put the following in the correct order • Put the following pictures in the correct order as they occur during mitosis: • Answer: c,b,d,a

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