1. Ch. 8 The Cellular Basis of Reproduction and Inheritance © 2012 Pearson Education, Inc.

2. Cell division plays many important roles in the lives of organisms  Cell division is reproduction at the cellular level  Requires duplication of chromosomes  Sorting new sets of chromosomes into the resulting pair of daughter cells.  Cell division is used for: –Reproduction of single-celled organisms –Growth of multicellular organisms from a fertilized egg into an adult –Repair and replacement of cells –Sperm and egg production. © 2012 Pearson Education, Inc.

3. Cell division plays many important roles in the lives of organisms  Living organisms reproduce by two methods. –Asexual reproduction –Does not involve sperm & egg –Offspring are identical to the parent –Involves inheriting all genes from one parent –Sexual reproduction –Requires fertilization of an egg by sperm –Offspring look similar to parents, but show variations in traits –Involves inheriting a unique set of genes from its two parents.

4.  Prokaryotes (bacteria and archaea) reproduce by binary fission “dividing in half”  Binary Fission Occurs in Three Steps: 1.Duplication of the chromosome and separation of the copies, 2.Continued elongation of the cell and movement of the copies 3.Division into two daughter cells.  The chromosome of a prokaryote is:  A singular circular DNA molecule & associated proteins  Much smaller than eukaryotic DNA Prokaryotes reproduce by binary fission © 2012 Pearson Education, Inc.

5. Figure 8.2A_s3 Plasma membrane Cell wall Duplication of the chromosome and separation of the copies Continued elongation of the cell and movement of the copies Prokaryotic chromosome 1 2 3 Division into two daughter cells

6. THE EUKARYOTIC CELL CYCLE AND MITOSIS © 2012 Pearson Education, Inc.

7.  Eukaryotic cells store most of their genes on multiple chromosomes within the nucleus.  Eukaryotic chromosomes are composed of chromatin = one long DNA molecule and proteins The large, complex chromosomes of eukaryotes duplicate with each cell division © 2012 Pearson Education, Inc.

8.  Before a eukaryotic cell divides, it duplicates all of its chromosomes, resulting in two copies called sister chromatids joined by a centromere.  When a cell divides, sister chromatids separate from each other, (now called chromosomes) and sort into separate daughter cells. The large, complex chromosomes of eukaryotes duplicate with each cell division © 2012 Pearson Education, Inc.

9. Figure 8.3B Sister chromatids Chromosomes Centromere Chromosome duplication Sister chromatids Chromosome distribution to the daughter cells DNA molecules

10.  The cell cycle extends from the time a cell is first formed until its own division and consists of two stages 1.Interphase: –G 1 —growth, increase in cytoplasm –S—duplication of chromosomes –G 2 —growth, preparation for division 2.Mitotic phase: Nuclear Division –Mitosis—nuclear division –Cytokinesis—division of cytoplasm The cell cycle multiplies cells © 2012 Pearson Education, Inc.

11.  Mitosis (nuclear division) progresses through a series of stages): –prophase/prometaphase –metaphase –anaphase –telophase  Cytokinesis Cell division is a continuum of dynamic changes © 2012 Pearson Education, Inc.

12. INTERPHASE MITOSIS Prophase Prometaphase Centrosome Early mitotic spindle Chromatin Fragments of the nuclear envelope Kinetochore Centrosomes (with centriole pairs) Centrioles Nuclear envelope Plasma membrane Chromosome, consisting of two sister chromatids Centromere Spindle microtubules

13. MITOSIS Anaphase Metaphase Telophase and Cytokinesis Metaphase plate Cleavage furrow Nuclear envelope forming Daughter chromosomes Mitotic spindle

14.  Prophase –Microtubules (mitotic spindle) begin to emerge from centrosomes –Spindle microtubules attach to kinetochores, moving chromosomes towards center of the cell –Chromatin condenses into chromosomes (now visible with a light microscope) –Nucleoli, nuclear envelope disappear Cell division is a continuum of dynamic changes © 2012 Pearson Education, Inc.

15.  Metaphase –Chromosomes align at the cell equator in preparation for division Cell division is a continuum of dynamic changes © 2012 Pearson Education, Inc.

16.  Anaphase –Sister chromatids separate at centromeres and daughter chromosomes are moved to opposite poles of the cell –The cell elongates due to lengthening of nonkinetochore microtubules. Cell division is a continuum of dynamic changes © 2012 Pearson Education, Inc.

17.  Telophase –The cell continues to elongate –The nuclear envelope forms around chromosomes at each pole, establishing daughter nuclei –Chromosomes uncoil and nucleoli reappear. –The spindle disappears. Cell division is a continuum of dynamic changes © 2012 Pearson Education, Inc.

18.  Cytokinesis differs in animal and plant cells.  In animal cells a cleavage furrow forms from a contracting ring of microfilaments, interacting with myosin; the cleavage furrow deepens to separate the contents into two cells. Cell division is a continuum of dynamic changes © 2012 Pearson Education, Inc.

19. Cytokinesis Cell wall of the parent cell Daughter nucleus Cell wall Plasma membrane Vesicles containing cell wall material Cell plate forming New cell wall Cell plate Daughter cells  In plant cells a cell plate forms in the middle, from vesicles containing cell wall material; the cell plate grows outward to reach the edges, dividing the contents into two cells, each with a plasma membrane and cell wall.

20.  The cells within an organism’s body divide and develop at different rates.  Cell division is controlled by –the presence of essential nutrients –growth factors, proteins that stimulate division –density-dependent inhibition, in which crowded cells stop dividing –anchorage dependence, the need for cells to be in contact with a solid surface to divide. Anchorage, cell density, and chemical growth factors affect cell division © 2012 Pearson Education, Inc.

21. Cultured cells suspended in liquid The addition of growth factor

22. Receptor protein Signal transduction pathway Growth factor Relay proteins Plasma membrane E XTRACELLULAR F LUID C YTOPLASM G 1 checkpoint G1G1 S M G2G2 Control system

23. Anchorage Single layer of cells Removal of cells Restoration of single layer by cell division

24.  Cancer cells escape controls on the cell cycle.  Cancer cells divide rapidly, often in the absence of growth factors, spread to other tissues through the circulatory system, and grow without being inhibited by other cells. CONNECTION: Growing out of control, cancer cells produce malignant tumors © 2012 Pearson Education, Inc.

25.  A tumor is an abnormally growing mass of body cells. –Benign tumors remain at the original site. –Malignant tumors spread to other locations, a process called metastasis. CONNECTION: Growing out of control, cancer cells produce malignant tumors © 2012 Pearson Education, Inc.

26. Tumor Glandular tissue GrowthInvasionMetastasis Lymph vessels Blood vessel Tumor in another part of the body

27. MEIOSIS AND CROSSING OVER © 2012 Pearson Education, Inc.

28.  In humans, body (somatic) cells have 23 pairs of homologous chromosomes: One member of each is from each parent.  One pair = sex chromosomes = X and Y; they differ in size and genetic composition.  The other 22 pairs of chromosomes are autosomes; they have the same size and genetic composition. Chromosomes are matched in homologous pairs

29.  Homologous chromosomes are matched in length, centromere position, and gene locations (except X & Y)  A locus (plural, loci) is the position of a gene.  Different versions of a gene may be found at the same locus on maternal and paternal chromosomes = alleles Chromosomes are matched in homologous pairs © 2012 Pearson Education, Inc.

30. Pair of homologous chromosomes Locus Centromere Sister chromatids One duplicated chromosome

31.  Humans and many animals and plants are diploid meaning that their body cells that have two sets of chromosomes, one from each parent. Gametes have a single set of chromosomes © 2012 Pearson Education, Inc.

32.  Meiosis is a process that converts diploid nuclei to haploid nuclei. –Diploid cells have two homologous sets of chromosomes –Haploid cells have one set of chromosomes  Meiosis occurs in sex organs, producing gametes= sperm and eggs  Fertilization is the union of sperm and egg.  The zygote has a diploid chromosome number, one set from each parent Gametes have a single set of chromosomes © 2012 Pearson Education, Inc.

33. Haploid gametes (n  23) Egg cell Sperm cell Fertilization n n Meiosis Ovary Testis Diploid zygote (2n  46) 2n2n Mitosis Key Haploid stage (n) Diploid stage (2n) Multicellular diploid adults (2n  46)

34.  Meiosis I – Prophase I – events occurring in the nucleus. –Chromatin condenses –Homologous chromosomes synapse and the pairs, with four chromatids, is called a tetrad –Nonsister chromatids exchange genetic material by crossing over Meiosis reduces the chromosome number from diploid to haploid © 2012 Pearson Education, Inc.

35.  Genetic recombination is the production of new combinations of genes due to crossing over  Crossing over is an exchange of corresponding segments between nonsister chromatids on homologous chromosomes Crossing over further increases genetic variability © 2012 Pearson Education, Inc. Tetrad Chiasma

36. Centrosomes (with centriole pairs) Centrioles Sites of crossing over Spindle Tetrad Nuclear envelope Chromatin Sister chromatids Fragments of the nuclear envelope Chromosomes duplicate Prophase I I NTERPHASE: M EIOSIS I

37. Centromere (with a kinetochore) Spindle microtubules attached to a kinetochore Metaphase plate Homologous chromosomes separate Sister chromatids remain attached Metaphase I Anaphase I M EIOSIS I

38.  Meiosis I  Metaphase I – Tetrads align at the cell equator  Anaphase I – Homologous pairs separate and move toward opposite poles of the cell  Telophase I /cytokinesis- Duplicated chromosomes have reached the poles, a nuclear envelope re-forms around chromosomes  Each nucleus has the haploid number of chromosomes Meiosis reduces the chromosome number from diploid to haploid © 2012 Pearson Education, Inc.

39. A pair of homologous chromosomes in a diploid parent cell A pair of duplicated homologous chromosomes Sister chromatids 2 2 I NTERPHASE M EIOSIS I M EIOSIS II  Meiosis II follows meiosis I without chromosome duplication  The two haploid cells enter meiosis II. 1

40. Meiosis reduces the chromosome number from diploid to haploid  Meiosis II  Interphase II  Prophase II - Chromosomes coil and become compact (if uncoiled after telophase I )  Nuclear envelope, if re-formed, breaks up again  Metaphase II – Duplicated chromosomes align at the cell equator  Anaphase II sister chromatids separate and chromosomes move toward opposite poles  Telophase II Chromosomes have reached the poles of the cell, a nuclear envelope forms around each set of chromosomes, with cytokinesis, four haploid cells are produced

41. Figure 8.13_right Cleavage furrow Telophase I and CytokinesisProphase II Metaphase II Anaphase II M EIOSIS II : Sister chromatids separate Sister chromatids separate Haploid daughter cells forming Telophase II and Cytokinesis

42. Figure 8.13_4 Prophase II Metaphase II Anaphase II M EIOSIS II : Sister chromatids separate Sister chromatids separate Haploid daughter cells forming Telophase II and Cytokinesis

43.  Mitosis and meiosis both –Begin with diploid parent cells –Have chromosomes that are duplicated once during interphase  The end products of mitosis and meiosis differ –Mitosis produces two genetically identical diploid somatic daughter cells –Meiosis produces four genetically unique haploid gametes Mitosis and meiosis have important similarities and differences © 2012 Pearson Education, Inc.

44. Figure 8.14 Prophase Metaphase Duplicated chromosome (two sister chromatids) M ITOSIS Parent cell (before chromosome duplication) Chromosome duplication Chromosome duplication Site of crossing over 2n  4 Chromosomes align at the metaphase plate Tetrads (homologous pairs) align at the metaphase plate Tetrad formed by synapsis of homologous chromosomes Metaphase I Prophase I M EIOSIS I Anaphase Telophase Sister chromatids separate during anaphase 2n2n 2n2n Daughter cells of mitosis No further chromosomal duplication; sister chromatids separate during anaphase II nnnn Daughter cells of meiosis II Daughter cells of meiosis I Haploid n  2 Anaphase I Telophase I Homologous chromosomes separate during anaphase I ; sister chromatids remain together M EIOSIS II

45.  Genetic variation in gametes results from independent orientation at metaphase I and random fertilization Independent orientation of chromosomes in meiosis and random fertilization lead to varied offspring © 2012 Pearson Education, Inc.

46.  Independent orientation at metaphase I –Each pair of chromosomes independently aligns at the cell equator –There is an equal probability of the maternal or paternal chromosome moving towards a given pole –The number of combinations for chromosomes packaged into gametes is 2 n where n = haploid number of chromosomes Independent orientation of chromosomes in meiosis and random fertilization lead to varied offspring © 2012 Pearson Education, Inc.

47. Possibility A Two equally probable arrangements of chromosomes at metaphase I Possibility B Metaphase II Gametes Combination 3Combination 4Combination 2Combination 1

48.  Random fertilization – The combination of each unique sperm with each unique egg increases genetic variability Independent orientation of chromosomes in meiosis and random fertilization lead to varied offspring © 2012 Pearson Education, Inc.

49. ALTERATIONS OF CHROMOSOME NUMBER AND STRUCTURE © 2012 Pearson Education, Inc.

50.  A karyotype is an ordered display of magnified images of an individual’s chromosomes arranged in pairs.  Karyotypes –are often produced from dividing cells arrested at metaphase of mitosis –allow for the observation of –homologous chromosome pairs –chromosome number, sex –chromosome structure A karyotype is a photographic inventory of an individual’s chromosomes © 2012 Pearson Education, Inc.

51. Figure 8.18_s3 Blood culture Packed red and white blood cells Centrifuge Fluid Hypotonic solution Fixative White blood cells Stain 3 2 1

52. 4

53. Centromere Sister chromatids Pair of homologous chromosomes 5 Sex chromosomes

54.  Trisomy 21 called Down syndrome, produces a characteristic set of symptoms, which include: –characteristic facial features –short stature –involves the inheritance of three copies of chromosome 21 and is the most common human chromosome abnormality. An extra copy of chromosome 21 causes Down syndrome © 2012 Pearson Education, Inc.

55. Figure 8.19A Trisomy 21

56.  Nondisjunction is the failure of chromosomes or chromatids to separate normally during meiosis. This can happen during –meiosis I, if both members of a homologous pair go to one pole or –meiosis II if both sister chromatids go to one pole.  Fertilization after nondisjunction yields zygotes with altered numbers of chromosomes. Accidents during meiosis can alter chromosome number © 2012 Pearson Education, Inc.

57. Figure 8.20A_s3 Nondisjunction M EIOSIS I M EIOSIS II Normal meiosis II Gametes Number of chromosomes Abnormal gametes n  1 n  1

58. Figure 8.20B_s3 Normal meiosis I M EIOSIS I M EIOSIS II Nondisjunction Abnormal gametesNormal gametes n  1n  1 nn

59.  Chromosome breakage can lead to rearrangements that can produce –genetic disorders or, if changes occur in somatic cells, cancer.  These rearrangements may include –a deletion, the loss of a chromosome segment, –a duplication, the repeat of a chromosome segment, –an inversion, the reversal of a chromosome segment, or –a translocation, the attachment of a segment to a nonhomologous chromosome that can be reciprocal Alterations of chromosome structure can cause birth defects and cancer

60. Chromosome 9 Chromosome 22 Reciprocal translocation “Philadelphia chromosome” Activated cancer-causing gene  Chronic myelogenous leukemia (CML) A common leukemia that affects cells that give rise to white blood cells (leukocytes), and results from part of chromosome 22 switching places with a small fragment from a tip of chromosome 9.

61. Deletion Duplication Inversion Reciprocal translocation Homologous chromosomes Nonhomologous chromosomes

62. Number of chromosomal duplications Number of cell divisions Number of daughter cells produced Number of chromosomes in the daughter cells How the chromosomes line up during metaphase Genetic relationship of the daughter cells to the parent cell Functions performed in the human body MitosisMeiosis