1. Cell Cycle-Mitosis, Sexual Reproduction-Meiosis & Inheritance-Genetics

2. CHROM…words Chromatin – uncoiled DNA + proteins
Chromosome – coiled DNA + proteins (Looks like an X)
Chromatid – only half of a chromosome
Sister chromatids – Two chromatids joined together, by a centromere, to form a chromosome

3. Chromatin

4. Cell Cycle 4 distinct periods
What does the cell spend most of its life doing?
Do you think DNA synthesis is an “expensive” process? Why or why not?
Mitosis is a continuous process described in 5 phases:

5. p. 128

6. Cell Cycle Four stages to the cell cycle
Growth period - Interphase includes: G1
S Stage G2
Division period - Includes:
Mitosis

7. Interphase: Known as the growth period Majority of cells life
Three stages within Interphase G1
S Stage G2

8. G1 Stage #1
Chromosomes are not visible under a microscope - because they are uncoiled, therefore called chromatin
Proteins are quickly made

9. S Stage Stage #2 Chromatin is replicated in the nucleus
Chromatin divides to form sister chromatids which are connected by centromeres

10. G2 Stage #3 Chromatin shortens and coils Organelles are made
Most proteins made are for mitosis
Animals - centriole pair replicates and prepares to form spindle fibers.

11. Interphase Information
Busiest phase of cell cycle
What are the three parts?
When are the chromosomes replicated?
When is the most protein production?
When are organelles made?
When are cell parts made?
Which is the longest stage of interphase?
Which is the shortest stage of interphase?

14. Prophase
Metaphase
Anaphase

15. Mitosis the process of organizing and distributing nuclear DNA
Early Prophase
the chromatin begins to condense into chromosomes
Martini pgs 97-98

16. Mitosis Late Prophase Aster one of the centriole pairs moves
to the opposite side of the cell.
microtubules begin to grow from
the centrioles building the
spindle apparatus.
the nuclear envelope begins to
dissolve.
Aster
Martini pgs 97-98

17. Mitosis Transition to Metaphase the spindle apparatus
forms completely and
the chromosomes attach
Martini pgs 97-98

18. Mitosis Metaphase the chromosomes line up along the equator of the
cell
Martini pgs 97-98

19. Mitosis Anaphase the sister chromatids are taken to opposite
poles of the
Martini pgs 97-98

20. Mitosis Telephase The chromosomes decondense back into chromatin
Nuclear membranes form around each set of unduplicated chromosomes
Martini pgs 97-98

21. Cytokinesis
The actual division of the cytoplasm usually occurs toward the end of telephase.

22. Somatic cell division results in two identical cells
Martini pgs 97-98

23. Mitosis is regulated by growth factors

24. Mitosis is inhibited by suppressor genes
For example: p53

25. Cancer
When the rate of cell division (mitotic rate) is greater than that of cell death in a tissue
Martini pgs

26. Screening for Cell Division Cycle (cdc) Mutants
cdc mutants 1) continue cell growth
2) arrest with a single cell morphology
i.e. at a defined cell cycle stage

27. Temperature Sensitive Yeast cdc Mutant
Permissive
Temperature
Restrictive
Temperature

30. Cell Division Mitosis (used during somatic cell division)
Diploid to Diploid
creates 1 new somatic daughter cell
parent and daughter cell are genetically identical
Meiosis (used during production of sex cells)
Diploid to Haploid (1 copy of chromosomes)
creates 4 reproductive cells (eggs or sperm)
new combination of chromosomes (mix of mom and dad)

31. creating genetic diversity
Sexual Reproduction:
creating genetic diversity

32. creating genetic diversity
Sexual Reproduction:
creating genetic diversity
As opposed to asexual reproduction which makes genetic clones.

33. An overview: from germ cell to babies
Germ Cells – diploid cells of the reproductive organs.
Gametes – haploid cells (sperm/egg = 23 chromosomes) made from germ cells by a process called meiosis.
babies – conceived when the nuclei of sperm and egg join to make 46 total chromosomes (23
homologous pair)

34. Germ Cells: homologous chromosomes
All somatic cells have 46 chromosomes (23 homologous pairs), one copy of each pair is inherited from the mother and the other from the father.

35. Because of homologous chromosomes there are 2 copies of each gene.
From Egg
From Sperm

36. One gene can come in different varieties.
Allele: variant forms of the same gene.
Can you think of an example of a gene that has more than 1 allele?

37. Sexual Reproduction Shuffles Alleles
Through sexual reproduction, offspring inherit new combinations of alleles, which lead to variations in traits

38. Gamete Formation ovaries testes Gametes are sex cells (sperm, eggs)
Gametes are formed when germ cells in reproductive organs undergo meiosis.
ovaries
testes

39. Two important things happen during meiosis
The number of chromosomes is cut in half (46 to 23)
The alleles are rearranged so that any offspring produced are genetically different from the parents.

40. chromosome number in gametes
n is equal to the total number of chromosomes in a cell
Germ cells (like somatic cells) are diploid (2n)
Gametes are haploid (1n)

41. How does 1 germ cell (2n) become 4 gametes (1n)?
Two consecutive cell divisions, but only 1 replication of the DNA
1. Meiosis I Meiosis II
DNA replication:
cell division w/o replication

42. Meiosis I
Prophase I
Each duplicated chromosome pairs with homologue (mom’s copy with dad’s copy)
Homologues form tetrads during synapsis and swap segments (cross over) to increase genetic variation
Each chromosome becomes attached to spindle

43. Crossing Over
The maternal and paternal chromosomes swap a segments while they are paired.

44. Outcome of Crossing Over
After crossing over, a chromosome will contain both maternal and paternal segments
Creates new allele combinations in offspring

45. Meiosis I Metaphase I The spindle apparatus is fully formed
the homologous chromosomes (tetrads) line up randomly along the equator of the cell

46. mom’s chromosome
Random Alignment 1 2 3
dad’s chromosome or
In Meiosis I the chromosomes line up at the equator randomly
This means that the genetic contributions from mom and dad can be mixed up in the gametes. or or

47. Meiosis I Anaphase I homologous chromosomes segregate
the sister chromatids remain attached

48. Meiosis I
Telophase I
chromosomes arrive at opposite ends of the cell and cytokinesis separates the cytoplasm

49. Meiosis I results in:
2 genetically different diploid (2n) cells

50. Prophase II
Microtubules attach to the kinetochores of the duplicated chromosomes

51. Metaphase II
Duplicated chromosomes line up at the spindle equator, midway between the poles

52. Anaphase II
Sister chromatids separate to become independent chromosomes

53. Telophase II The chromosomes arrive at opposite ends of the cell
A nuclear envelope forms around each set of chromosomes
The result is four haploid cells (gametes)

54. three polar bodies (haploid) primary oocyte (diploid)
Oogenesis
three polar bodies (haploid)
first polar body
oogonium (diploid)
primary oocyte (diploid)
secondary oocyte
ovum (haploid)
Meiosis I,
Cytoplasmic Division
Meiosis II,
Cytoplasmic Division
Growth

55. Spermatogenesis secondary spermatocytes spermatids (haploid)
sperm (mature, haploid male gametes)
spermato- gonium
(diploid )
primary spermatocyte (diploid)
Growth
Meiosis I
Meiosis II
cell differentiation, sperm formation

56. Fertilization
Male and female gametes unite and their nuclei fuse together
combining the chromosomes.
Fusion of two haploid nuclei
produces a diploid nucleus in the
zygote

57. Factors that contribute to variation among Offspring
Crossing over during prophase I
Random alignment of chromosomes at metaphase I
Random combination of gametes at fertilization
Genetic variation in offspring is important. It protects the species from environmental changes (like a new disease).

58. Mitosis vs. Meiosis