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Cellular Reproduction and DNA

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  1. Cellular Reproduction and DNA • Offspring receive their traits from their parents- but sometimes the child looks nothing like the parents

  2. Cellular Reproduction and DNA • Offspring receive their traits from their parents- but sometimes the child looks nothing like the parents • Lamarkian biology- characteristics such as height, strength, and weight are determined by the activities of the parents. (FAIL.)

  3. The Father of Modern Genetics • Gregor Mendel (1822-1884): an Austrian monk • Gave first real explanation for how traits are passed on to offspring • Conducted meticulous experiments on 29,000 pea plants • Mendel's work was rejected during his lifetime, and it wasn't widely accepted until the 1930's and 1940's • Genetics- the science that studies how characteristics get passed from parent to offspring

  4. Genes, Chromosomes, and DNA • DNA governs an organism's traits and characteristics • DNA's main function is to tell the cell what proteins to make

  5. Genes, Chromosomes, and DNA • DNA governs an organism's traits and characteristics • DNA's main function is to tell the cell what proteins to make • Not every organism's traits are completely determined by a person's genes • Genetic tendency- a range of possible characteristics set by DNA

  6. Genetic Tendencies • People have a certain capacity for musical ability, or athletic ability • Some people choose to fight against genetic predispositions such as alcoholism and obesity • Consider an alcoholic whose father is also an alcoholic- you could argue that the son learned this through father, or that alcoholism is in his genes, or it's a combination of both

  7. Genetic Tendencies • People have a certain capacity for musical ability, or athletic ability • Some people choose to fight against genetic predispositions such as alcoholism and obesity • Consider an alcoholic whose father is also an alcoholic- you could argue that the son learned this through father, or that alcoholism is in his genes, or it's a combination of both • Gay rights activists are searching for a “gay gene” in order to justify their behavior • However, many defects are transmitted through genes (eg. Down Syndrome, cystic fibrosis, color blindness) • Even if a “gay gene” were found, a gene cannot force a person into a homosexual lifestyle- he is able to choose how to live, just like an alcoholic can choose not to drink alcohol

  8. Developmental Factors • Characteristics completely from DNA: hair color, blood type • DNA alone does not determine who you are or what you will become • DNA provides the general framework within which you decide who you will become

  9. Developmental Factors • Characteristics completely from DNA: hair color, blood type • DNA alone does not determine who you are or what you will become • DNA provides the general framework within which you decide who you will become • Genetic factors- traits determined by DNA • Environmental factors- nonbiological factors that are involved in a person's surroundings (family, friends, school, choices they make) • Spiritual factors- factors in a person's life determined by the quality of their relationship with God • There is still much debate over how much influence each of these factors has over a person's development

  10. Genes and DNA • Gene- a section of DNA that codes for the production or portion of protein, thereby causing a trait

  11. Genes and DNA • Gene- a section of DNA that codes for the production or portion of protein, thereby causing a trait • The tasks that a cell can complete depend upon the proteins it produces • If a cell produces certain proteins, it's a nerve cell, if it make other proteins, it's a blood cell

  12. Genes and DNA • Gene- a section of DNA that codes for the production or portion of protein, thereby causing a trait • The tasks that a cell can complete depend upon the proteins it produces • If a cell produces certain proteins, it's a nerve cell, if it make other proteins, it's a blood cell • A cell knows what proteins it should produce because the DNA tells it what to make

  13. DNA and RNA

  14. DNA and RNA DNA • Sugar: deoxyribose • Structure: double helix • Nucleotides: adenine, guanine, cytosine, thymine • More stable, less likely to experience changes during duplication (less mutations) RNA Sugar: ribose Structure: single strand Nucleotides: adenine, guanine, cytosine, thymine Less stable

  15. Protein Synthesis- Part 1: Transcription • 1.Transcription- building an RNA strand from a section of DNA • RNA copies DNA by attaching corresponding nucleotide bases • RNA is like a camera that produces a negative image (light in places it should be dark) • T- A • C- G • A- U

  16. Protein Synthesis- Part II: Translation • 2. Translation: the process of translating the nucleotide bases into amino acid sequences

  17. Protein Synthesis- Part II: Translation • 2. Translation: the process of translating the nucleotide bases into amino acid sequences • Messenger RNA (mRNA)- RNA that performs transcription and then goes to the ribosomes

  18. Protein Synthesis- Part II: Translation • 2. Translation: the process of translating the nucleotide bases into amino acid sequences • Messenger RNA (mRNA)- RNA that performs transcription and then goes to the ribosomes • Transfer RNA (tRNA)- contains an anticodon bonded to an amino acid • Anticodon- three nucleotide base sequence on tRNA

  19. Protein Synthesis- Part II: Translation • Codon- a sequence of three nucleotide bases on mRNA that refers to specific amino acid

  20. Protein Synthesis- Part II: Translation • Codon- a sequence of three nucleotide bases on mRNA that refers to specific amino acid • Translation repeats until all amino acids that are called for by codons are linked together • DNA → RNA → protein

  21. Protein Synthesis- Part II: Translation • Codon- a sequence of three nucleotide bases on mRNA that refers to specific amino acid • Translation repeats until all amino acids that are called for by codons are linked together • DNA → RNA → protein • A given amino acid can be “called for” by several different codons. eg. cysteine can be called by UGC or UGU • However, a single codon cannot call for more than one amino acid (eg. UGU is only for cysteine) • Protein Synthesis

  22. DNA and RNA • Exons- part of DNA with instructions for making a protein • Introns- separates exons, must be removed before it becomes mRNA

  23. DNA and RNA • Exons- part of DNA with instructions for making a protein • Introns- separates exons, must be removed before it becomes mRNA • Introns are also known as “junk DNA” because they don't appear to serve any purpose • DNA is very thin- .0000002mm • If all the DNA from one cell we strung together end to end, it would be six feet long. All DNA in body: 67 billion miles (16x distance of Pluto to Sun)

  24. How DNA is Packaged • Histones- proteins that act as spools which wind up small stretches of DNA • Nucleosomes- beads of DNA wrapped around histone

  25. How DNA is Packaged • Histones- proteins that act as spools which wind up small stretches of DNA • Nucleosomes- beads of DNA wrapped around histone • Chromosome- network of DNA coils and proteins • In nucleus

  26. How DNA is Packaged • Histones- proteins that act as spools which wind up small stretches of DNA • Nucleosomes- beads of DNA wrapped around histone • Chromosome- network of DNA coils and proteins • In nucleus • Chromatin- strands of chromosomes, RNA, and proteins • Condensed chromosome- most compact version of DNA • Humans: 46 chromosomes horse: 64, crayfish: 200

  27. Mitosis and Interphase • Mitosis- a process of asexual reproduction in eukaryotic cells • Interphase- time interval between cellular reproduction • Chromosomes not condensed • Cell spends most of its time in this stage • DNA remains in its chromatin form, except when making proteins • Cell cycle- cycle between interphase and mitosis

  28. Mitosis • In order to reproduce, chromosomes must duplicate • Sister chromatids- duplicate chromosomes • The centrioles also duplicate, then mitosis starts

  29. 1. Prophase -duplicated chromosomes coil into their condensed form Centromere- the region that joins two sister chromatids -aster- microtubules extended from centrioles -as centrioles migrate, the microtubules grow, producing spindle fibers - Spindle fibers make up the mitotic spindle

  30. 2. Metaphase -chromosomes are lined up along equatorial plane

  31. 2. Metaphase -chromosomes are lined up along equatorial plane 3. Anaphase -microtubules separate the sister chromatids from each other -sister chromatids are pulled to opposite sides

  32. 2. Metaphase -chromosomes are lined up along equatorial plane 3. Anaphase -microtubules separate the sister chromatids from each other -sister chromatids are pulled to opposite sides 4. Telophase -spindle begins to disintergrate -plasma membrane begins to constrict along equatorial plane

  33. 4. Telophase -spindle begins to disintergrate -plasma membrane begins to constrict along equatorial plane -two cells begin to form -nuclear membrane forms around each chromosome - chromosomes uncoil from their condensed form back into chromatin -the end result is two identical daughter cells

  34. More About Mitosis • Each daughter cell gets at least one of each organelle • If the two cells have only one organelle between them, the organelle is split • DNA can build up or make new organelles as needed • The mitochondria has its own DNA so it can replicate itself

  35. More About Mitosis • Each daughter cell gets at least one of each organelle • If the two cells have only one organelle between them, the organelle is split • DNA can build up or make new organelles as needed • The mitochondria has its own DNA so it can replicate itself • Mitosis is a form of asexual reproduction • Every eukaryotic organism performs mitosis • Mitosis produces new cells as the organism grows, and replaces dead cells • Millions of red blood cells die every minute

  36. More About Mitosis • Plant mitosis: due to cell wall, the plasma membrane can’t constrict • Cellulose is formed in the middle, producing the cell well • Also no centrioles are in the plant cells

  37. Chromosomes • Karyotype- the figure produced when chromosomes of a species during metaphase are arranged according to their homologous pairs • Homologous pairs- chromosomes that are very similar but not identical • Sex chromosomes- a pair of chromosomes which can be used to distinguish between the sexes • XX: female • XY: male

  38. Diploid and Haploid Cells • each homologue has exactly the same number of genes as its partner • For example, the gene for blood type can be found on chromosome #9- on one homologue, the gene might be for blood type A and on the other, O. • Diploid cell- a cell with chromosomes that come in homologous pairs • Haploid cell- a cell that has only one representative of each pair

  39. Diploid and Haploid Cells • Even species that have diploid cells will have some haploid cells • Diploid number (2n)- total number of chromosomes in a diploid cell • 46 for human • Haploid number- (n) number of homologous pairs in a diploid cell • 23 for human

  40. Sexual Reproduction • Meiosis – the process by which a diploid (2n) cell forms gametes (n) • -each parent contributes 23 chromosomes • In meiosis, diploid cells get split into haploid cells called gametes • Gametes- haploid cells produced by diploid cells for purpose of sexual reproduction • Female: egg (ovum) Male: sperm • Two gametes join together to form a|diploid cell that has 23 homologous pairs of chromosomes- zygote

  41. Meiosis I • Meiosis I- one diploid cell forms two haploid cells • -two begin meiosis, cell must duplicate DNA and centrioles • Prophase I- centrioles move to opposite sides of cell • DNA is exchanged between homologous chromosomes (cross over) • Mitotic spindle forms • Metaphase I- single microtubule for each pair- chromatids stay intact

  42. Meiosis I • Anaphase I- homologous pairs are pulled to either side • Telophase I- plasma membrane constricts along equatorial plane • -two haploid cells are formed • -though each cell has 46 chromosomes, the cells are considered haploid because the chromosomes are paired with an exact duplicate, leaving 23 unique chromosomes

  43. Meiosis • Prophase II- both cells have their centrioles duplicate and form a spindle • Metaphase II- chromosomes line up along equatorial plane • -chromosomes attach to each chromatid • Anaphase II- the microtubules pull the chromosomes away fromtheir duplicates • Telophase II- plasma membrane constricts along equatorial plane, forming two pairs of haploid cells

  44. Mitosis vs. Meiosis Mitosis: one diploid cell forms two duplicate diploid cells Meiosis: diploid to haploid -One diploid cell forms 4 haploid cells

  45. Spermatogenesis -In males, meiosis produces sperm cells - At the end of meiosis II, flagella emerges on each of the four haploid cells

  46. Oogenesis Oogenesis: meiosis in females -at the end of telophase I, one of the two cells produced takes most of the cytoplasm and organelles -After meiosis II, one of the big cells from Meiosis I takes most of the cytoplasm and organelles -the end result is one large gamete (Egg cell) and three smaller polar bodies - when the sperm burrows into the egg, it forms a diploid cell called a zygote

  47. Viruses • Virus- non-cellular infectious agent • 1. has genetic material (RNA or DNA) inside a protective protein coat • 2. cannot reproduce on its own • -a virus hijacks a cell in order to reproduce • -because a virus cannot reproduce on its own, it’s not alive

  48. Lytic Pathway Virus attaches to bacterium Virus injects own genetic material Virus DNA instructs bacteria to make viral proteins and genetic material Viruses form in cell Cell ruptures, releasing several viruses

  49. Viruses • Some viruses, like HIV, can inject genes into the cell and lie dormant for several years before the lytic pathway starts • Viruses: chicken pox, flu, mumps, cold, mumps, measles, AIDS, cold sores, some forms of cancer • Viruses affect plants, animals, and bacteria

  50. The Immune System • Phagocytic cells- purpose is to engulf and destroy pathogens (eg. White blood cells) • Lymph nodes- a place for phagocytic cells to gather • -lymph carries pathogens through the lymph nodes, where the phagocytic cells destroy them • Antibodies- specialized proteins that aid in destroying infectious agents