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Difference Between Mitosis and Meiosis

Learn about the types of reproduction, the process of fertilization, and the differences between mitosis and meiosis. Understand the roles of somatic cells and gamete cells in chromosome distribution. Gain knowledge about the stages of meiosis and the importance of genetic variation in sexual reproduction.

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Difference Between Mitosis and Meiosis

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  1. Meiosis H BIOLOGY LANE TECH February 2018

  2. What is the difference between Mitosis and Meiosis?

  3. Types of Reproduction • Asexual • One parent produces genetically identical offspring • Ex: body cells (mitosis), bacteria • Sexual • Two parents produce genetically different offspring through fertilization • Different type of cell division must be used to create an egg & a sperm! (meiosis) 46 23 + 23

  4. What is Fertilization? • Fertilization: A sperm cell and an egg cell fuse together • Creates a zygote which is a fertilized egg • Half the genetic information is from “dad” and half is from “mom”

  5. Diploid Male (2n=46) Diploid Female (2n=46) MEIOSIS Egg Cell (n=23) Sperm Cell (n=23) FERTILIZATION Zygote (2n=46) Embryo (2n=46) MITOSIS begins  helps grow the embryo into a human!

  6. 2 Groups of Cells in our Body • Somatic Cells: • Also called “Body Cells” • Every cell in your body, except for your sex cells (eggs and sperm) • Divide by Mitosis continuously until death • Gametes: • Sex cells (eggs and sperm)

  7. Chromosomes within Cells • Remember, within our cells, we have chromosomes! • These are found…. in the nucleus! • Different species have different numbers of chromosomes • How many chromosomes do humans have? • 46 (23 pairs of chromosomes)

  8. Chromosomes within Cells • Recall those 2 groups of cells we talked about earlier…? • 1st - Somatic Cells • ContainAutosomal Chromosomes – code for physical traits (in pairs) • 22 pairs = 44 chromosomes total • 2nd - Gamete Cell(s) • Containsex chromosomes – determine gender (in pairs) • 1 pair = 2 chromosomes total

  9. Sex chromosomes • Found in gamete cells  determines gender (male/female) • 2 forms  X and Y • Mom’s egg always gives an “X” • Sperm can give “X” or “Y” • Results in: • Males: XY • Females: XX FUN FACT: Why was King Henry VIII a big jerk?!

  10. Somatic vs. Gametes Sex chromosomes from GAMETE CELLS ALL AUTOSOMAL CHROMOSOMES  from SOMATIC CELLS

  11. FUN FACT: Meiosis in men creates 4 sperm cells, whereas meiosis in women creates 1 (large!) egg cell Only 1 3 1 2 4

  12. Another Difference between Somatic & Gamete Cells? • Somatic and Gamete Cells contain different amounts of chromosomes (and therefore, DNA) • Two types: • Haploid (n) • Diploid (2n)

  13. Haploid vs. Diploid • Haploid (n): • Produced by meiosis • These are GAMETES (sex cells) • Contain a single set of chromosomes  23 chromosomes (n) • Diploid (2n): • A complete set(2 sets total) of homologouschromosomes  1 from mom, 1 from dad • Contain 23 pairs in humans = 46 chromosomes FUN FACT: in humans, n = 23….

  14. What are Homologous Chromosomes? • HOMOLOGOUS – pair of chromosomes that are the same shape, size, and have the same gene pattern • NOT identical  you get one set from mom and one set from dad • 23 homologous pairs = 46 chromosomes One pair of homologous chromosomes = tetrad

  15. What is Meiosis? • Meiosis: • Part of Sexual reproduction • Increases genetic variation • Type of cell division that produces 4 haploid daughter cells • Goal: each daughter cell has half the number of chromosomes as parent cell • Only occurs in sex organs (testes, ovaries)

  16. Meiosis Overview2 Cell Divisons • Meiosis I • Prophase I • Separates Homologous Pair • Metaphase I • Anaphase I • Telophase I • Meiosis II • Prophase II • Separates sister chromatids • Metaphase II • Anaphase II • Telophase II

  17. Meiosis 1 • Prophase I • Nuclear Envelope breaks down • Chromatin condenses – why is this important? HINT: which of these would be easier to accurately divide in half?

  18. Meiosis 1 • Prophase I (con’d) • Homologous chromosomes stick together • 2 homologous chromosomes = a tetrad = 4 chromatids • Crossing Over happens! • Sister chromatids exchange genetic material

  19. Meiosis 1 • Metaphase I: • Tetradsline up in the middle of the cell • Anaphase I: • Tetrads(homologous pairs) split and move to opposite poles of cell

  20. Meiosis 1 • Telophase I: • Spindle fibers disappear • Nucleus envelope reappears • Cytokinesis • 2 Haploid daughter cells (1n)

  21. Meiosis 1 Summary TELOHASE II TELOHASE I DNA info from mom and dad wrapped into 1 chromosome (92 chromatids = 46 chromatids worth of information from both parents) PROPHASE I

  22. Meiosis 2 • Prophase II • Nuclear Envelope breaks down, centrosomes and centrioles move to pole ends and spindle fibers assemble (same as in Prophase I except NO Crossing Over) • Metaphase II • 23 chromosomes align at the cell equator, each chromosome still has TWO sister chromatids • Anaphase II • Sister chromatids pull apart • Telophase II • Nuclear membranes re-form around each set of chromosomes, spindle fibers break apart 4 cells total now have 23 chromosomes  a combo from both mom and dad

  23. Prophase I - Duplicate Homologues Pair Up = Tetrad

  24. Metaphase I – Tetrads Align in the Middle

  25. Anaphase I – Tetrads Separate

  26. Telophase I – Nucleus reforms. 23 chromosomes (46 chromatids) in each of TWO new cells

  27. Prophase II – 46 chromatids move toward equator plate

  28. Metaphase II – 23 Chromatid Pairs align between the poles

  29. Anaphase II – 46 chromatids are pulled apart and become 46 chromosomes

  30. Telophase II – 23 chromosomes (haploid 1n) in each cell!

  31. How is it All Related?

  32. Complications of Meiosis: Genetic Disorders • Caused by an abnormality in an individual’s DNA • How do these abnormalities occur? • Non-disjunction • Addition or subtraction of chromosome or a set of chromosomes • Mutations • Change to DNA sequence (gene)

  33. Non-Disjunction QUESTION: Is it possible for non-disjunction to occur and still end up with a healthy individual?

  34. Non-Disjunction • Non-disjunction- failure of the chromosomes to separate properly in meiosis I or II • What are some disorders caused by non-disjunction? • Downs Syndrome • Trisomy 21 • Patau Syndrome • Trisomy 13 • Edwards Syndrome • Trisomy 18 • Klinefelter’s Syndrome • XXY • Turner Syndrome • Monosomy X

  35. What is a Karyotype? • Karyotype: • Display of chromosomes (condensed)

  36. Human Karyotype -

  37. What’s the problem?

  38. What’s the problem?

  39. What’s the problem?

  40. Klinefelter’s Syndrome

  41. Klinefelter Syndrome

  42. Turner Syndrome

  43. Turner Syndrome

  44. Inheritance Patterns of Disorders • Codominant Inheritance • Sickle cell anemia • Dominant Inheritance • Huntington’s Disease • Recessive Inheritance • Cystic fibrosis (recessive) • Maple syrup urine disorder (recessive) • Congenital hypothyroidism (recessive)

  45. Sickle Cell Anemia • Hemoglobin is the O2 carrying protein in red blood cells • SCA is an inherited blood disease where hemoglobin clumps together  causes red blood cells to stiffen and curl into a sickle/crescent shape  because of this, the RBC cannot transport O2 effectively

  46. Huntington’s Disease • Huntington’s disease • Develops in middle age, death soon follows • Deterioration of nervous system, uncontrollable movements until person dies  • Found on Chromosome 4 • Chromosome 4 spans more than 186 million base pairs • HD is a dominantgene… • …this means any child of an affected person has a 50% chance of inheriting the disease

  47. Recessive Disorders • Over a thousand human genetic disorders are known to have Mendelian inheritance patterns • Cystic Fibrosis • Excess mucus in lungs, digestive tract, liver • More susceptible to pneumonia, infection • Early death ~ average age of 37 • Tay-Sachs • Lipid accumulation in brain cells, mental retardation • Blindness, death in childhood

  48. Recessive Disorders • The majority of people with recessive disordersare born to parents who are heterozygous and do not have the recessive disorder • People who have one copy of the allele for a recessive disorder, but do not show any symptoms are called carriers

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