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Cells and Genes

Cells and Genes. Cell Theory. In 1838, two German Scientists Theodor Schwann and Mattias Jakob Schleiden put forward a theory on the structure of living organisms. This theory had a number of observations, including:.

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Cells and Genes

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  1. Cells and Genes

  2. Cell Theory In 1838, two German Scientists Theodor Schwann and Mattias Jakob Schleiden put forward a theory on the structure of living organisms. This theory had a number of observations, including: • The cell is the unit of structure, physiology, and organization in living things. • The cell retains a dual existence as a distinct entity and a building block in the construction of organisms. • These observations have become parts of what is known as the Cell Theory

  3. Cells • Cells are the smallest living subunits of an organism • Some organisms are unicellular, meaning that they are comprised of only one cell • Ex bacteria, amoebas, etc

  4. Cells • Other organisms are multicellular, meaning that they are comprised of many cells • Ex animals, birds, insects, human beings • Human beings are said to contain about 200 different types of cells – each adapted to a specific task

  5. Cytology • The study of the formation, structure, and function of cells • Focus on different aspects including: • Chromosomes • DNA • Genetics • Cytology = cyt/o(cell), -logy (study of)

  6. Cell Structure

  7. DNA • DNA stands for deoxyribonucleic acid • Has two strands that twist together to form a double helix • DNA is read to create the proteins encoded in our more than 20,000 genes

  8. Chromosomes • Chromosomes are pieces of DNA found within the nucleus of a cell • Normally cannot be seen individually • When a cell is preparingto divide, the DNA condenses into dense rod-like structures that are copied before division occurs

  9. Chromosomes • Human body (somatic) cells normally have 46chromosomes arranged into 23 pairs • Sex cells or gametes contain 23 single chromosomes • Chromosomes contain regions called genes, that can be “read” to give the cell instructions,or to produce a necessarysubstance

  10. Karyotype • A karyotypeimage is a map of the number and appearance of chromosomes within a human cell • The chromosomes are treated with chemicals so that characteristic bands of light and dark areas can be seen • It may be requested if there is any suspicion of genetic disorder

  11. Genetics • Genetics is the study of how genes are transferred from generation to generation • Genesis means producing or origin • Geneticists study not only how genes function in normal conditions, but also how they function to create disease

  12. Genetic Inheritance • Humans normally receive two copies (alleles) of every gene – one from their mother, and one from their father • Gametes have one copy of each chromosome • When a male gamete (sperm) fertilizes a female gamete (ovum), the DNA mingles • The resulting fetus develops with this mix of maternal and paternal DNA

  13. Inheritance • Dominant alleles will cause their trait to be displayed even if only one copy of the gene is received

  14. Inheritance • Recessive alleles will only cause their trait to be displayed if two copies of the gene are received

  15. Genetic Disorders • Genetic disorders are usually due to a genetic mutation • Inherited • Acquired • Mutations can be due to: • Deletions • Substitutions • Additions

  16. Trisomy 21 (Down Syndrome)

  17. Kleinfelter Syndrome

  18. Genetic Disorders • Down Syndrome (trisomy 21) • Cystic Fibrosis (recessive) • Hemophilia (X-linked recessive) • Huntington Disease (dominant) • Phenylketonuria (recessive) • Tay-Sachs Disease (recessive) • OsteogenesisImperfecta (dominant)

  19. Cell Division • Mitosis • Normal Cell replication • One cell with a diploid number of chromosomes (46) divides into two cells, each with the diploid number of chromosomes • Produces identical cells • Used to replace cells in the body • Mitosis Animation

  20. Cell Division • Meiosis • Cell replication to form gametes • Gametes are sex cells – the ovum and the spermatozoon • Each gamete contains half of the usual number of chromosomes (23)

  21. Cell Replication • Meiosis has two parts: • Meiosis I – begins when the chromosomes duplicate • The chromosomes group together so that all chromosomes of one type are joined together (at this point the copies of the chromosomes can exchange information) • The chromosomes then separate in a process similar to Mitosis • Meiosis II – the process occurs again, without the chromosomes replicating to create the gametes • Mitosis results in 2 daughter cells, Meiosis results in 4 daughter cells

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