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III. Uniting Genetics and Cell Biology

Explore the key discoveries in genetics and cell biology, from Friedrich Miescher isolating nucleic acid to Sutton and Boveri's Chromosomal Theory of Heredity. Understand terms like chromatin and chromosomes, and learn about ploidy and chromosome sets.

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III. Uniting Genetics and Cell Biology

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  1. III. Uniting Genetics and Cell Biology

  2. III. Uniting Genetics and Cell Biology A. Early Studies - 1869 - Friedrich Miescher isolated phosphate rich compound in the nucleus of the cell called nuclein (nucleic acid).

  3. III. Uniting Genetics and Cell Biology A. Early Studies - 1869 - Friedrich Miescher isolated phosphate rich compound in the nucleus of the cell called nuclein (nucleic acid). - 1878 – Walther Flemming studied dividing cells and coined the terms ‘mitosis’ and saw that the ‘chromatin’ was separated into thread-like bodies (called ‘chromosomes’ by Waldeyer-Hartz)… and concluded that nuclei came from pre-existing nuclei.

  4. III. Uniting Genetics and Cell Biology A. Early Studies - 1869 - Friedrich Miescher isolated phosphate rich compound in the nucleus of the cell called nuclein (nucleic acid). - 1878 – Walther Flemming studied dividing cells and coined the terms ‘mitosis’ and saw that the ‘chromatin’ was separated into thread-like bodies (called ‘chromosomes’ by Waldeyer-Hartz)… and concluded that nuclei came from pre-existing nuclei. - 1883 – Edouard Van Beneden Described the movement of chromosomes during meiosis (gamete formation).

  5. III. Uniting Genetics and Cell Biology A. Early Studies - 1900 – Tschermak, Correns, and deVries Three scientists who, as a consequence of their work in plant hybridization, rediscovered Mendel’s work. Hugo DeVries Erich von Tschermak Carl Correns

  6. III. Uniting Genetics and Cell Biology A. Early Studies - 1900 – Tschermak, Correns, and deVries Three scientists who, as a consequence of their work in plant hybridization, rediscovered Mendel’s work. Tschermak was an agronomist who worked with garden peas Correns was an eminent botanist. Although he confirmed Mendel’s work, he also was the first to document cytoplasmic inheritance – a pattern of inheritance governed NOT by chromosomal genes, but rather by hereditary factors in the cytoplasm. In this case, by genes in the chloroplasts that are only passed from the female parent. DeVries was also an eminent botanist. Coined the term pangenes, confirmed Mendel’s particulate heredity, and also proposed that evolution proceeded largely by massive changes to organisms, not by gradual selection. Hugo DeVries

  7. III. Uniting Genetics and Cell Biology A. Early Studies - 1902 – Sutton and Boveri United Mendel’s Principles of heredity (Segregation and Independent Assortment) with chromosomal movement during gamete formation Each proposed the “Chromosomal Theory of Heredity” – that the hereditary particles or ‘genes’ were parts of chromosomes, that segregated from one another, in an independent manner, during gamete formation; and thus explained Mendelian patterns of heredity. UNITING THE MOVEMENT OF CHROMOSOMES IN CELLS WITH PATTERNS OF HEREDITY Theodor Boveri Walter Sutton

  8. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes

  9. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms chromatin: indistinguishable, diffuse chromosomes

  10. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms chromatin: indistinguishable, diffuse chromosomes chromosome: condensed strand of chromatin, either: unreplicated (one DNA double-helix) OR Replicated (two double-helices)

  11. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms chromatin: indistinguishable, diffuse chromosomes chromosome: condensed strand of chromatin, either: unreplicated (one DNA double-helix) OR Replicated (two double-helices) A A A A single DNA double-helix, bound with the associated proteins (pink), is called a ‘chromatid’. An unreplicated chromosome has one chromatid. A replicated chromosome has two chromatids that are identical

  12. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms “Ploidy” refers to the “information content” in the cell… how many ‘sets’ of chromosomes are there?

  13. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms “Ploidy” refers to the “information content” in the cell… how many ‘sets’ of chromosomes are there? - in simplistic terms, if a cell has ‘one gene for every trait’ = haploid (1n) A b C d

  14. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms “Ploidy” refers to the “information content” in the cell… how many ‘sets’ of chromosomes are there? - in simplistic terms, if a cell has ‘one gene for every trait’ = haploid (1n) - we then make reference to the NUMBER of chromosomes present: “1n = 2” A b C d

  15. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms “Ploidy” refers to the “information content” in the cell… how many ‘sets’ of chromosomes are there? - in simplistic terms, if a cell has ‘one gene for every trait’ = haploid (1n) - we then make reference to the NUMBER of chromosomes present: “1n = 2” - In eukaryotes, gametes are haploid (typically) A b C d

  16. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms “Ploidy” refers to the “information content” in the cell… how many ‘sets’ of chromosomes are there? - in simplistic terms, if a cell has ‘one gene for every trait’ = haploid (1n) - we then make reference to the NUMBER of chromosomes present: “1n = 2” - In eukaryotes, gametes are haploid (typically) - bacteria and archaeans have one circular chromosome and so are haploid organisms. A b C d

  17. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms “Ploidy” refers to the “information content” in the cell… how many ‘sets’ of chromosomes are there? - in simplistic terms, if a cell has ‘one gene for every trait’ = haploid (1n) - we then make reference to the NUMBER of chromosomes present: “1n = 2” - when haploid gametes fuse during fertilization, a zygote with two genes for every trait is formed. This cell is DIPLOID, 2n = 4. A a b B C C d D

  18. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms “Ploidy” refers to the “information content” in the cell… how many ‘sets’ of chromosomes are there? - in simplistic terms, if a cell has ‘one gene for every trait’ = haploid (1n) - we then make reference to the NUMBER of chromosomes present: “1n = 2” - when haploid gametes fuse during fertilization, a zygote with two genes for every trait is formed. This cell is DIPLOID, 2n = 4. - NOTE that the two chromosomes of the same color are not IDENTICAL. They govern the same traits, but the genes that they have for these traits can be different alleles (forms of a gene) that influence that trait in different ways. A a b B C C d D

  19. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms “Ploidy” refers to the “information content” in the cell… how many ‘sets’ of chromosomes are there? - in simplistic terms, if a cell has ‘one gene for every trait’ = haploid (1n) - we then make reference to the NUMBER of chromosomes present: “1n = 2” - when haploid gametes fuse during fertilization, a zygote with two genes for every trait is formed. This cell is DIPLOID, 2n = 4. - NOTE that the two chromosomes of the same color are not IDENTICAL. They govern the same traits, but the genes that they have for these traits can be different alleles (forms of a gene) that influence that trait in different ways. Chromosomes that govern the same traits = HOMOLOGOUS A a b B C C d D

  20. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms “Ploidy” refers to the “information content” in the cell… how many ‘sets’ of chromosomes are there? - Many organisms (indeed, maybe MOST flowering plant species) are POLYPLOID, and have several sets of chromosomes… like this Tetraploid (4n = 8). A a A A B b b b C C C C d D d d

  21. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms “Ploidy” refers to the “information content” in the cell… how many ‘sets’ of chromosomes are there? - Many organisms (indeed, maybe MOST flowering plant species) are POLYPLOID, and have several sets of chromosomes… like this Tetraploid (4n = 8). - when it makes gametes (with ½ the genetic info as the parent cell), it will make diploid gametes… so not ALL gametes are haploid. A a A A b B b b C C C C d D d d

  22. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle

  23. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle - Interphase: Poorly named – the cell is most active metabolically, growing, building proteins, replicating its DNA, and preparing for division.

  24. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle - Interphase: Poorly named – the cell is most active metabolically, growing, building proteins, replicating its DNA, and preparing for division. Chromosomes are diffuse – “chromatin” – DNA recipes are being ‘read’ and proteins are synthesized, or DNA is being replicated.

  25. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle - Interphase: Poorly named – the cell is most active metabolically, growing, building proteins, replicating its DNA, and preparing for division. Chromosomes are diffuse – “chromatin” – DNA recipes are being ‘read’ and proteins are synthesized, or DNA is being replicated. Three substages: G1, S, G2

  26. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle - Interphase: G1: the cell is most active metabolically, growing and building proteins appropriate for that cell. Cell may be “arrested” in this stage and not divide again (neurons, muscle). If so, it is more appropriately said that the cell has entered the G0 stage.

  27. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle - Interphase: G1: the cell is most active metabolically, growing and building proteins appropriate for that cell. Cell may be “arrested” in this stage and not divide again (neurons, muscle). If so, it is more appropriately said that the cell has entered the G0 stage. S: (“synthesis”) DNA replication occurs; each chromosome transitions from its unreplicated (one DNA double-helix) to its replicated (two DNA double-helices) state.

  28. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle - Interphase: G1: the cell is most active metabolically, growing and building proteins appropriate for that cell. Cell may be “arrested” in this stage and not divide again (neurons, muscle). If so, it is more appropriately said that the cell has entered the G0 stage. S: (“synthesis”) DNA replication occurs; each chromosome transitions from its unreplicated (one DNA double-helix) to its replicated (two DNA double-helices) state. G2: Preparatory for division; in animals, centrioles are made during this period. DNA is repaired (and errors made during replication) can be corrected before division.

  29. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle - Interphase: - “Checkpoints”:

  30. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle - Interphase: - “Checkpoints”: The transition from G1 is critical; if a cell crosses this ‘checkpoint’ late in G1, it is committed to dividing.

  31. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle - Interphase: - “Checkpoints”: The transition from G1 is critical; if a cell crosses this ‘checkpoint’ late in G1, it is committed to dividing. Likewise, the transition from G2 is critical, because the DNA will be passed to daughter cells in its present state.

  32. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle - Interphase: - “Checkpoints”: The transition from G1 is critical; if a cell crosses this ‘checkpoint’ late in G1, it is committed to dividing. Likewise, the transition from G2 is critical, because the DNA will be passed to daughter cells in its present state. If these checks are poorly regulated, cells can divide prematurely, before tissue specialization, forming a tumor. Also, the number of heritable mutations increases.

  33. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle - Interphase: - “Checkpoints”: - Division: either mitosis or meiosis

  34. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle 3. Mitosis

  35. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle 3. Mitosis • Prophase: • Chromosomes condense; become visible with a light microscope • Nuclear membrane breaks down • Attached at kinetochore (part of centromere) to spindle apparatus (actin strands of the cytoskeleton that have rearranged) Early Late

  36. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle 3. Mitosis • Metaphase: • Chromosomes aligned in center of cell, on the “metaphase plate”

  37. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle 3. Mitosis • Anaphase: • Spindles contract, pulling ‘sister chromatids’ apart. The microtubules are shortened metabolically, by cleaving subunits from the kinetochore end…”chewing it up”

  38. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle 3. Mitosis • Telophase: • Nuclear membranes reform around the chromosomes; the division of the genetic information (karyokinesis) is complete.

  39. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle 3. Mitosis • Telophase: • Nuclear membranes reform around the chromosomes; the division of the genetic information (karyokinesis) is complete. • Chromosomes become diffuse.

  40. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle 3. Mitosis • Telophase: • Nuclear membranes reform around the chromosomes; the division of the genetic information (karyokinesis) is complete. • Chromosomes become diffuse. • Cytokinesis (division of the cytoplasm) can occur.

  41. Cytokinesis (division of the cytoplasm) can occur. • In animal cells, this occurs by the cytoskeleton (actin and myosin, like in muscle cells) attaching to the inner surface of the membrane and contracting-like the pulling of a drawstring– creating a ‘cell furrow’

  42. Cytokinesis (division of the cytoplasm) can occur. • In plant cells, Golgi Bodies produce vesicles that move along the spindles to the metaphase plate where they coalesce; releasing their contents to form new membrane and a “cell plate” – a partition that expands and divides the cell in half.

  43. Cytokinesis (division of the cytoplasm) can occur. • In plant cells, Golgi Bodies produce vesicles that move along the spindles to the metaphase plate where they coalesce; releasing their contents to form new membrane and a “cell plate” – a partition that expands and divides the cell in half. • For the cells to grow, the cell wall weakens and the absorption of water causes the cells to swell; the cell wall fibers realign and harden as larger ‘boxes’.

  44. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle 3. Mitosis Summary: • Occurs after DNA replication

  45. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle 3. Mitosis Summary: • Occurs after DNA replication • Separates identical sister chromatids from one another; each daughter cells gets one

  46. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle 3. Mitosis Summary: • Occurs after DNA replication • Separates identical sister chromatids from one another; each daughter cells gets one • Produces daughter cells identical to one another, and identical to the parent cell (except for genetic mutations).

  47. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle 3. Mitosis Summary: • Occurs after DNA replication • Separates identical sister chromatids from one another; each daughter cells gets one • Produces daughter cells identical to one another, and identical to the parent cell (except for genetic mutations). • This is the process by which a zygote divides in 2, then 4, then 8 cells, etc… eventually producing a multicellular organism (like you or a blue whale) that may be composed of trillions of nearly identical body cells.

  48. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle 3. Mitosis Summary: • Occurs after DNA replication • Separates identical sister chromatids from one another; each daughter cells gets one • Produces daughter cells identical to one another, and identical to the parent cell (except for genetic mutations). • This is the process by which a zygote divides in 2, then 4, then 8 cells, etc… eventually producing a multicellular organism (like you or a blue whale) that may be composed of trillions of nearly identical body cells. • This is also the process by which asexual (or ‘clonal’) reproduction occurs; producing offspring identical to the parent (except for mutations).

  49. Video clips: http://www.youtube.com/watch?v=VlN7K1-9QB0

  50. III. Uniting Genetics and Cell Biology A. Early Studies B. Divisional Processes 1. Terms 2. Cell Cycle 3. Mitosis 4. Meiosis: Gamete Formation

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