1. Chapter 8 and 9
Lesson 1- Chromosomes Lesson 2- Cell Cycle Lesson 3-Mitosis Lesson 4-Meiosis

2. Chromosomes

3. Chromosomes
Structures made of DNA and associated proteins on which genes are located.

5. Sets of Chromosomes
Diploid-a cell that contains two sets of chromosomes. (2n)
Haploid- a cell that contains one set of chromosomes. (n)
The number of chromosomes in cells is constant within a species.

6. Each human cell normally has two pairs of 23 different chromosomes for a total of 46 chromosomes.
The 23 pairs of chromosomes differ in size, shape, and genetic content.
Each pair consists of two homologous chromosomes or homologues (one from each parent).

7. Homologous Example
xx XX 1 2
Within each homologous pair, the chromosomes are similar in size, shape, and genetic content. However, each pair is different from the next.

8. Autosomes
Are chromosomes that are not directly involved in determining the sex (gender) of an individual.
Of the 23 pairs of chromosomes, 22 pairs are called autosomes.

9. Sex (Gender) Chromosomes
Are chromosomes that are directly involved in determining the sex (gender) of an individual.
Of the 23 pairs of chromosomes, 1 pair is called sex chromosomes.
Males – XY
Females - XX

10. The sex of the offspring is determined by the male, who can donate either an X or Y chromosome.

11. The presence of all 46 chromosomes is essential for normal development and function.

12. Chromosome Variations
A genetic disorder is caused by an abnormality in an individual's DNA.
Abnormalities can range from a small mutation in a single gene to the addition or subtraction of an entire chromosome or set of chromosomes.

13. RESULTS: Down’s Syndrome Turner’s Syndrome Huntington’s Disease
Sickle Cell Anemia
Cystic Fibrosis
And other genetic disorders . .

14. The Cell Cycle

15. The Eukaryotic Cell Cycle

16. The eukaryotic cell cycle consists of phases of growth, DNA replication, preparation for cell division, and division of the nucleus and cytoplasm.

17. Stages of the Cell Cycle
First Growth (G1) Phase
Synthesis (S) Phase
Second Growth (G2) Phase
Mitosis (M)
Cytokinesis (C)

18. The Cell Cycle: Interphase
A cell spends (90%) of its time in Interphase
First Growth (G1) Phase: cell grows rapidly and carries out its routine functions.
Cells that are not dividing remain in the G1 phase.
Synthesis (S) Phase: cell’s DNA is copied.
Second Growth (G2 )Phase: preparations are made for the nucleus to divide.

19. process during cell division in which the cytoplasm divides.
Final Stages
Mitosis:
process during cell division in which the nucleus of a cell is divided into two nuclei.
Cytokinesis:
process during cell division in which the cytoplasm divides.

20. Importance of Mitosis and Cytokinesis
Mitosis and Cytokinesis produce new cells that are identical to the original cells and allow organisms to grow, replace damaged tissues, and, in some organisms, reproduce asexually.

21. How do cells know when to divide?
How is the cell cycle controlled?

22. Check Points
Cells have check points that control the phases of the cell cycle.
At each checkpoint, feedback signals from the cell can trigger the next phase of the cell cycle.

23. Cell Cycle Review Define cell cycle.
List the 5 phases of the cell cycle.
List the 3 phases of the cell cycle.
What phases make up Interphase?
How much time does a cell spend in Interphase?
What regulates the cell cycle?
Do all cells go through all stages of the cell cycle?

24. Mitosis

25. Mitosis
Process in which the nucleus of the cell divides and maintains the parental chromosome number for daughter cells.

26. Stages of Mitosis
PROPHASE
METAPHASE
ANAPHASE
TELEPHASE
P M A T

27. Prophase Chromosomes coil up and become visible.
Nuclear envelope dissolves and a spindle forms

28. Metaphase
Chromosomes move to the center of the cell and line up along the equator (middle).
Spindle fibers link the chromosomes to opposite poles.

29. Anaphase Centromeres divide (split)
Chromatids are pulled away to opposite poles of the cell

30. Telophase Nuclear envelopes form around the chromosomes at each pole.
Two new cells are visible.

31. Cytokinesis
During cytokinesis, the cytoplasm of the cell membrane grows to enclose each cell, forming two separate cells as a result.

32. Asexual and Sexual Reproduction

33. Reproduction
the process of producing offspring.
Types:
Asexual Reproduction
Sexual Reproduction

34. Sexual Reproduction
Definition: reproduction in which gametes from opposite sexes or mating types unite to form a zygote (fertilized egg).
Occurs in eukaryotic organisms.
Two parents each form haploid reproductive cells.
-sperm cells contain 23 chromosomes (Father)
-egg cells contain 23 chromosomes (Mother)

35. Sexual reproduction contd.
Both parents contribute genetic material
The offspring has traits of both parents but are not exactly like either parent.

36. Advantages of Sexual Reproduction
Makes different combinations of genes among individuals.
Leads to greater genetic diversity.

37. Asexual Reproduction
Definition: reproduction that involves only one parent and results in genetically identical offspring.
Occurs in Prokaryotes and some eukaryotes.
Parent passes copies of all of its genes to each of its offspring

38. Asexual reproduction contd.
There is no fusion of haploid cells
= clone (an organism that is genetically identical to its parent)

39. Types of Asexual Reproduction
Binary fission - reproduction in which the parent separates into one or more individuals of equal size.
Fragmentation -reproduction in which the body breaks into several pieces.
Budding - reproduction in which new individuals split off from existing ones.

40. Asexual Reproduction
Advantages
Simple
Allows organisms to reproduce rapidly
Organisms do not need a mate
Disadvantages
DNA is identical to that of the parent
Organism may not be able to adapt to a new environment

41. Let’s Review
Define reproduction
Some organisms have ______ parents, while others have ________.
Distinguish between asexual reproduction and sexual reproduction.
An individual produced by asexual reproduction is a _____________.
List the types of asexual reproduction.
List the disadvantages/advantages of asexual reproduction.

42. Meiosis

43. A form of nuclear division that creates four haploid cells from one diploid cell.
Meiosis reduces the chromosome number and creates genetic diversity.
Involves two rounds of cell division-meiosis I and meiosis II.

44. Homologous Chromosomes
Points to Remember
Homologous Chromosomes
Are two separate chromosomes
One comes from the mother AND one comes from the father.
Very similar in size, shape, and genetic content
divided in meiosis I.
Sister Chromatids
Half of a duplicated chromosome
Two chromatids together
joined at the centromere
divided in meiosis II.

45. Meiosis 

46. Nuclear membrane breaks down
Meiosis – Prophase I
Nuclear membrane breaks down
Centrosomes and centrioles move to opposite sides of the cell
Spindle fibers start to assemble
Chromosomes condense and homologous chromosomes pair up.

47. Meiosis – Metaphase I
Homologous chromosome pairs are randomly lined up along the middle of the cell
This arrangement mixes up the chromosomal combinations and helps create and maintain genetic diversity.

48. sister chromatids are still connected.
Meiosis – Anaphase I
Paired homologous chromosomes separate and move to opposite sides of the cell
sister chromatids are still connected.

49. Chromosomes are in two groups at opposite sides of the cell.
Meiosis – Telophase I
Chromosomes are in two groups at opposite sides of the cell.
Cell divides into two haploid cells.

50. Nuclear membrane breaks down
Meiosis – Prophase II
Nuclear membrane breaks down
Centrosomes and centrioles move to opposite sides of the cell
Spindle fibers assemble

51. Spindle fibers align the chromosomes along the cell’s equator.
Meiosis – Metaphase II
Spindle fibers align the chromosomes along the cell’s equator.

52. Meiosis – Anaphase II
The sister chromatids are pulled apart from each other and move to opposite sides of the cell.

53. Meiosis – Telophase II
Nuclear membrane forms around each set of chromosomes at opposite ends of the cell
Spindle fibers break apart

54. Meiosis -- Cytokinesis
Cytoplasm and organelles finish replicating and the cell divides into two.
Cell membrane forms between the new cells.
Four haploid cells are formed.

55. Mitosis Overview

56. Meiosis Overview