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Biology

Biology. Meiosis. Remember from Chapter 1: CHARACTERISTICS OF LIVING THINGS ALL LIVING THINGS __________. REPRODUCE. Remember from Chapter 7, there are basically 2 types of cells__________ and ____________. EUKARYOTIC. PROKARYOTIC. Now let ’ s review Ch 10. Mitotic Cell Division

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Biology

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  1. Biology Meiosis

  2. Remember from Chapter 1:CHARACTERISTICS OF LIVING THINGSALL LIVING THINGS __________ REPRODUCE

  3. Remember from Chapter 7, there are basically 2 types of cells__________ and ____________ EUKARYOTIC PROKARYOTIC

  4. Now let’s review Ch 10.......... Mitotic Cell Division • Mitosis makes two identical daughter cells from one Parent cell • Bacteria and other prokaryotes may use mitosis to reproduce – called Binary Fission • This is asexual reproduction

  5. ASEXUAL REPRODUCTION Bacteria reproduce using BINARY FISSION This is mitosis!

  6. Budding isused by plants and some animals to reproduce asexually (mitosis) Hydra Regeneration is another way some animals reproduce asexually (mitosis) Planaria

  7. MITOSIS identical Produces cells that are __________ copies of parent cell

  8. Major Events in Mitosis

  9. Chromosome number must be maintained in animals. • Many plants have more than two copies of each chromosome.

  10. Mitosis and meiosis are types of nuclear division that make different types of cells. • Mitosis makes more diploid cells.

  11. 2 MITOSIS-in conclusion identical • Makes ___ cells genetically _________ to parent cell & to each other • Makes _________cells • Makes __________ • Used by organisms to: increase size of organism, repair injuries, and replace worn out cells 2n (diploid) SOMATIC (body)

  12. ADVANTAGES OF ASEXUAL REPRODUCTION Can make offspring faster Don’t need a partner

  13. ADVANTAGES OF ASEXUAL REPRODUCTION Works great for making new skin cells, blood cells, and any of the other body cells that need to be replaced Our body cells are called Somatic cells (repeat word)

  14. DISVANTAGES OF ASEXUAL REPRODUCTION ALL ALIKE No genetic diversity within a population One disease can wipe out whole population

  15. Question….if not asexual, then how can we reproduce?

  16. Sexual Reproduction Sexual reproduction is when two gametes (sex cells) fuse together to make a zygote.

  17. SEXUAL REPRODUCTION In humans, (and in many other organisms), sexual reproduction combines the genetic material from the gametes of 2 parents (sperm & egg) into a zygote -develops into offspring that are genetically __________ from parents DIFFERENT

  18. Let’s review sexual reproduction • In sexual reproduction, there are two parents. • Each parent has a gamete, or sex cell to donate to the offspring. • Each gamete has one set of chromosomes. • The two gametes come together (fertilization) to form one new cell called a Zygote. • This Zygote will grow and divide to become a unique organism.

  19. ADVANTAGES OF SEXUAL REPRODUCTION Allows for variation in population Individuals can be different Provides foundation for EVOLUTION Allow species adapt to changes in their environment

  20. EGG +  SPERM If egg and sperm cells had the same number of chromosomes as other body cells . . . baby would have too many chromosomes!

  21. MEIOSIS is the way we can avoid this problem. Meisosis makes cells with half the number of chromosomes for sexual reproduction

  22. sex cells (sperm) (egg) Sex Cells (also called germ cells) • Germ cells develop into_ gametes. • Germ cells are located in the ovaries and testes of humans and other animals. • Gametes are sex cells:__________. • Gametes have DNA that is passed to the offspring. egg and sperm

  23. Haploid (n) cells have one copy of every chromosome.(Remember diploid cells have two copies) • Gametes are haploid. • Human gametes have 22 autosomes and 1 sex chromosome.

  24. Haploid cells develop into mature gametes. • Gametogenesis is the production of gametes. • Gametogenesis differs between females and males. • Sperm become streamlined and motile. • Sperm primarily contribute DNA to an embryo.

  25. Haploid cells develop into mature gametes. • Gametogenesis differs between females and males. • Eggs contribute DNA, cytoplasm, and organelles to an embryo. • During meiosis, the egg gets most of the contents; the other cells form polar bodies.

  26. KEY CONCEPT Gametes have half the number of chromosomes that body cells have.

  27. DIPLOID & HAPLOID DIPLOID 2n Most cells have 2 copies of each chromosome = ______________ (one from mom; one from dad) All BODY (___________) cells are diploid HOMOLOGOUSCHROMOSOMES SOMATIC

  28. HOMOLOGOUS Chromosomes • SAME SIZE • SAME SHAPE • CARRY GENES for the SAME TRAITS • BUT ______________! (Don’t have to have the SAME CHOICES) NOT IDENTICAL

  29. DIPLOID & HAPLOID HAPLOID 1n Some cells have only one copy of each chromosome = _____________ Fertilization between egg and sperm occurs in sexual reproduction. All gametes (sperm and egg) cells are haploid

  30. SO……what is a chromosome? • main organelle involved in the Cell Cycle • Found in the nucleus • Contains genetic material (DNA) • Has 2 major parts-a centromere and sister chromatids

  31. There are two types of Chromosomes. • Your body cells have 23 pairs of chromosomes. • Homologous pairs of chromosomes have the same structure. • For each homologous pair, one chromosome comes from each parent.

  32. There are two types of Chromosomes. • Chromosome pairs 1-22 are autosomes. • Sex chromosomes, X and Y, determine gender in mammals.

  33. Humans have 46 chromosomes (23 pair) • Cats have 38 chromosomes (19 pair) • Chickens have 78 chromosomes (39 pair) • Horses have 64 chromosomes (32 Pair) • Potatoes have 48 chromosomes (24 pair) • Goldfish have100 chromosomes (50 pair) • Fruit fly has 8 (4 pair) • Corn has 20 (10 pair) • Peas have 14 (7 pair) • Mosquitoes have 6 chromosomes (3 pair) • Mice have 40 chromosomes (20 pair) • Elephants have 56 chromosomes (28)

  34. So Again…… • The zygote of humans have 23 pairs of chromosomes (or 46 individual chromosomes) • 23 chromosomes come from each parent • 23 + 23 = 46 • Humans have 46 chromosomes

  35. The process of Meiosis- The Formation of Sex Cells

  36. Meiosis makes haploid cells from diploid cells. • Meiosis occurs in sex cells. • Meiosis produces gametes.

  37. I. Introduction to Meiosis A. Purpose - to make sex cells for reproduction. B. Why can’t mitosis do this? Remember….mitosis would make too many chromosomes.

  38. MEIOSIS 4 • Makes ____ cells genetically different from parent cell & from each other • Makes _____ cells • Makes ______________ • Used for ____________ 1n Germ cells OR Gametes (sperm & eggs) sexual reproduction

  39. WHAT MAKES MEIOSIS DIFFERENT ? Crossing Over, Segregation, and Independent Assortment ALL are ways MEIOSIS results in =______________________________ So daughter cells are ______________ from parents and from each other GENETIC RECOMBINATION different

  40. WHAT MAKES MEIOSIS DIFFERENT ? • Homologous chromosomes pair up during ________________ = ______________ PROPHASE I SYNAPSIS This group of FOUR (4) chromatids is called a _________________ TETRAD

  41. WHAT MAKES MEIOSIS DIFFERENT? CROSSING OVER 1. Exchange of DNA betweenhomologous pairs = _____________during PROPHASE I Separates gene choices and Allows shuffling of genetic material

  42. CROSSING OVER • Allows for_________________ in different combinations • After crossing over, chromatid arms are________________ anymore rearranging of DNA NOT IDENTICAL

  43. WHAT MAKES MEIOSIS DIFFERENT ? Separation during ANAPHASE I -chromosome pairs separate SEGREGATION & INDEPENDENT ASSORTMENT

  44. SEGREGATION & CROSSING OVERtogether make even more combinations

  45. INDEPENDENT ASSORTMENT

  46. INDEPENDENT ASSORTMENTat ANAPHASE I Lots of different combinations are possible! This is why you don’t look exactly like your brothers and sisters even though you share the same parents!

  47. SO WHAT MAKES MEIOSIS DIFFERENT ? • SYNAPSIS & CROSSING OVER (PROPHASE I) 2. SEGREGATION & INDEPENDENT ASSORTMENT in Anaphase I create genetic recombination 3. Skip INTERPHASE II (NO S) CELL DIVIDES TWICE, BUT… ONLY COPIES DNA ONCE

  48. WHAT MAKES MEIOSIS DIFFERENT ? 3. Skip INTERPHASE II (No S) CELL DIVIDES TWICE, BUT … ONLY COPIES ITS DNA ONCE MITOSIS: P M A C G1 T S G2        MEIOSIS: ( I ) G1 A T C S G2 P M        ( II ) A P M T C    

  49. Workings of Meiosis A. Meiosis is - the formation of sex cells (eggs and sperm) 1. Gametes - another name for sex cells. A. Gametes have haploid chromosome number

  50. B. Meiosis is the making of eggs and sperm with half the number of chromosomes as the parent cell. 1. Female egg = 23 2. Male sperm = 23

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