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2014 Meiosis

2014 Meiosis. Intro. Look at the P unnett Square to the right. What is the probability of Homozygous dominant offspring? (Use the Same P unnett Square) What is the probability of heterozygous offspring?

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2014 Meiosis

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  1. 2014 Meiosis

  2. Intro • Look at the Punnett Square to the right. What is the probability of Homozygous dominant offspring? • (Use the Same Punnett Square) What is the probability of heterozygous offspring? • Imagine two heterozygous parents. Each has a dominant allele B for brown eyes and a recessive allele b for blue eyes. What is the phenotypic ratio? (do a Punnett Square and answer)

  3. Types of Body Cells (2n) Somatic Cells Gametes (n) Regular Body Cells Sex Cells

  4. Types of Body Cells (2n) Somatic Cells (2n) Divide By Mitosis Regular cell division of somatic cells (2n)  (2n) (2n) Regular Body Cells Have twice the chromosome number of the gamete (n) n n Half of the genetic material (n) came from mom and half from dad First created by fertilization Then divide by mitosis Humans have 46 total chromosomes or 23 pairs 23 came from mom and 23 from dad 23 Pairs of Homologous chromosomes

  5. Types of Body Cells Gametes (n) Sex Cells Have half of the chromosome number (n) of the mature organism (2n) (n) (2n) Germ cells are created by meiosis a reduction division (2n) mature individual  (n) gamete

  6. Types of Body Cells Divide By Mitosis Regular cell division of somatic cells (2n)  (2n) Meiosis Reduction Division (2n)  (n) Gametes (n) Somatic Cells (2n) Regular Body Cells Sex Cells Or Gametes Fertilization n n Half of the genetic material (n) came from mom and half from dad Fertilization (2n)  (n)

  7. Types of Body Cells • Somatic Cells • Regular body cells • Initially cell produced my fertilization (n) + (n)  (2n) • Divide by mitosis afterwards (2n)  (2n) • Skin Cells, Muscle Cells, etc. • Somatic cells have double the chromosome number (2n) • (n) represents the chromosome number of the organism • Human (n) is 23 • Human somatic cells have 2n or 2 x 23 = 46 chromosomes • one of the set (n) came from mom • and one set (other n) came from dad

  8. Diploid Cells (2n): (Somatic Cells) • Have pairs of homologous chromosomes • Represented by (2n) • Homologous chromosome pairs code for similar traits • Haploid Cells (n): (Gametes) • have half the chromosome number • Represented by a single (n)

  9. Human Karyotype Karyotype- picture of homologous pairs or chromosomes of an organism Humans have 23 pairs Different organisms have different numbers of pairs

  10. Dog Karyotype with 39 pairs Is this dog a boy or a girl?

  11. Male Karyotype 23rd Pair is the sex chromosomes Longer chromosome is an x and shorter a y XY Male

  12. Male Karyotype The 22 non sex determining chromosome pairs are called autosomes

  13. Female Karyotype XX Female

  14. Probability of having a female offspring

  15. Probability of having a female offspring • 50% chance of having a boy or girl • The males gamete determines this • Female only gives an X

  16. Questions • How many chromosomes do humans have? • How many pairs of chromosomes do humans have? • Chromosomes that code for the same traits are called _____________ ____________. • The 23rd pair in humans is called the ________________________. • If the 23 pair looked the same (XX), the individual would be a boy or girl?

  17. Questions 6. A _____________ is a picture of homologous pairs or chromosomes of an organism. 7. ______________ is the division that reduces specialized somatic cells to gametes. 8. Regular body cells undergo ____________ to divide. 9. Sex cells are also called _______________. 10. Regular body cells are also called ___________. 11. (2n) represents pairs of homologous chromosomes or __________ number. 12. (n) represents half the number of chromosomes in a somatic cell or _____________ number.

  18. Chromosome Reminder • Centromere- Middle of chromosome where sister chromatids are connected

  19. Alleles = alternative versions of a geneex. Brown eyes (B) or Blue Eyes (b)Found in specific locations (locus) of a specific chromosome

  20. Gregor Mendel’s (The father of genetics) Principles • The Principle of Unit Characters states that individuals pass information on as individual traits. • The Principle of Dominance states that some unit characters (genes) can mask the expression of others. • The Principle of Segregation states that each unit character (gene) separates into a different sex cell. • The Principle of Independent Assortment states that genes segregate according to chance; different genes separate INDEPENDENTLY of each other.

  21. Cell Cycle and Mitosis Reminder

  22. Mitosis • Prophase- 1st and longest phase of mitosis

  23. Mitosis • Metaphase- 2nd stage of mitosis

  24. Mitosis • Anaphase- 3rd stage of mitosis

  25. Mitosis • Telophase- 4th stage of mitosis

  26. Mitosis vs. Meiosis • Mitosis produces 2 genetically identical diploid (2n) daughter cells from a parent cell (2n) • One Round of Division • Sister Chromatids Separate • Exact Copies of Parent Produced • Only Mitosis • Meiosis produces 4 genetically different haploid (n) daughter cells from a parent cell (2n) • Two Rounds of Division • Meiosis I- Homologues Separate • Meiosis II – Chromatids Separate • Genetically Different Haploid Cells Produced • Meiosis I and Meiosis II • Reduction division (2n) to (n) in preparation for fertilization

  27. Meiosis • 2 Divisions Recombine Genes and Reduce the Chromosome Number • Division 1 (Homologous Chromosomes (Homologues) Separate) • Prophase I (Tetrad forms and genetic recombination takes place) • Metaphase I • Anaphase I (Pairs of Homologous Chromosomes (homologues) Separate) • TelophaseI and cytokinesis • Division 2 (Separates Sister Chromatids) • Prophase II • Metaphase II • Anaphase II (Sister Chromosomes Separate) • Telophase II and cytokinesis (4 genetically different haploid cells (n) result)

  28. Meiosis (Prophase I) Closer Look • Prophase I: • Homologous chromosomes form a tetrad • Tetrad synapsis can occur • Crossing over can occur • Crossing over- parts or chromosomes switch creating a genetic recombination

  29. Each letter represents a locus (position on the chromosome) • Crossing over shown here occurs during prophase I • Creates genetic variation in daughter cells

  30. In Males: 4 sperm are the end result of meiosis In Females: 3 of the haploid cells (called polar bodies) cannot be used for reproduction and only one egg results

  31. Spermatogenesis (Male) vs. Oogenesis (Female)

  32. Mistakes in Meiosis • What went wrong here? • What might the result be?

  33. Mistakes in Meiosis • Nondisjunction • Failure of homologues to separate properly

  34. Mistakes in Meiosis ENTIRE CHROMOSOME MISTAKES • Trisomy • Monosomy • Polyploidy • We’ll address individual GENE problems later…

  35. Mistakes in Meiosis • Trisomy – ONE EXTRA chromosome for just ONE chromosome number (3) and not a pair • Ex: Downs’ Syndrome (TRISOMY 21), XYY males Monosomy – ONE LESS CHROMOSOME for just ONE chromosome number • Ex: Turner’s Syndrome Polyploidy – a whole extra SET of chromosomes

  36. Trisomy

  37. Trisomy • Down’s syndrome

  38. XYY Male Karyotype

  39. XXY – may be male OR female (NOT both)Karyotype

  40. MonosomyTurner’s Syndrome • Monosomy X (Turners Syndrome) • Missing 1 chromosome = missing 1,000’s of genes!!! • Short neck • short stature • sterile, • Heart, kidney, bone, thyroid problems

  41. Monosomy • Myelodysplasia • Bone marrow disease • Spontaneous abortions

  42. Polypolid • In plants • tri & tetra

  43. Triploidy – Fatal in Animals

  44. Match • Monosomy • Trisomy • Polyploidy • These genetic disorders are created by ______________: homologues not separating correctly in prophase I of meiosis

  45. Match • Monosomy • Trisomy • Polyploidy • These genetic disorders are created by ______________: homologues not separating correctly in prophase I of meiosis

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