1. Notes on Chromosomes, Mitosis, & Meiosis

2. What is a chromosome?
Chromosomes = condensed DNA, same material, coiled more tightly into individual bundles
Chromatin = DNA that is uncoiled, unorganized, not individually visible
DNA is a large polymer composed of sugars, phosphates, & ‘bases’.

5. Chromosomes 400x 1 arm of a chromosome Chromatin w/o histone proteins
Chromatin wrapped >>
around histone proteins
DNA molecule
Chromatin w/o histone proteins

10. History of discovery
First seen and named “colored bodies” by Flemming in 1882
Similarity to Mendel’s factors noted by Sutton in 1902

11. Identifying chromosomes
number of chromosomes varies in different species
# of chromosomes does not correlate with anything
46 chromosomes in humans (23 pairs)
Each chromosome pair is named by a number, except…

12. Types of chromosomes ”Sex” chromosomes discovered by Morgan in 1908
called ‘X’ and ‘Y’ chromosomes because of different shapes
In humans and most animals
XX = female, XY = male

13. Types of chromosomes All the other chromosomes are called Autosomes,
These are known by number only

14. Cell Divsion

15. A cell spends most of its life growing and maintaining its molecules and organelles.
Cells that divide must double their contents during this growth period, or they would
become progressively smaller over several divisions and eventually lose key
components. This growth period is called interphase, and it lasts from 10 hours to an
animal’s lifetime, depending upon the type of cell.

16. Because DNA is the hereditary material, its duplication is a critical interphase activity
for potentially dividing cells. In early interphase, called the G1 (“Gap 1”) phase of the
cell cycle, no DNA is made in most cells.Then suddenly, as if on cue, DNA synthesis
begins at several sites on each chromosome and continues for several hours, stopping
when a copy of each chromosome has been made. This period of DNA synthesis is
known as S phase, and although highly variable, it typically lasts about 8-10 hours.

17. Following the S phase, there is another gap period, the G2 Phase (yellow), in which proteins that have a role in cell division are produced. Some of these proteins cause the chromosomes to condense into compact units, while others are involved in the breakdown of the nuclear membrane.

18. The M phase (red) of the cell cycle consists of two processes; mitosis, or nuclear division, followed by cytokinesis, or cytoplasmic division. These processes occur in animals as they develop from fertilized eggs and as they replace worn out tissues.

19. Replication of chromosomes
Replication of DNA = exact and complete duplication of original strand
Replication proceeds at a replication fork along both ‘halves’ of the original
Complementary strands are known as parent and daughter strands

20. Replication
of DNA

21. Mitosis
Reproduction of a somatic cell is an exact duplication of the original
ie. The daughter cells are exact clones
They have the same # of chromosomes
This # (different for each species) is known as the diploid number of chromosomes
Somatic cells must be distinguished from sex cells , found only in testes or ovaries

22. Mitosis is a special kind of cell division used by
eukaryote cells. You will find a series of diagrams in
your text & notes which shows the stages of mitosis;
these are: * prophase * metaphase * anaphase * telophase
Mitosis is really a division of the nucleus into two
identical nuclei. It is followed by cytokinesis which is
the division of the cytoplasm into two.

24. Phases of Mitosis interphase interphase telophase prophase anaphase
metaphase

25. Prophase
Metaphase
Anaphase
Telophase

27. Late
Telophase

28. A cell spends most of its life growing and maintaining its molecules and organelles.
Cells that divide must double their contents during this growth period, or they would
become progressively smaller over several divisions and eventually lose key
components. This growth period is called interphase, and it lasts from 10 hours to an
animal’s lifetime, depending upon the type of cell.

29. Interphase with symbols
for chromosomes

30. Prophase with symbols
for chromosomes

31. ‘Prometaphase’ with
symbols for chromosomes

32. Metaphase with symbols
for chromosomes

33. Anaphase with symbols
for chromosomes

34. Telophase with symbols
for chromosomes

35. Cytokinesis with symbols
for chromosomes

36. Mitosis

38. Mitosis
Animation

39. Mitosis animation U Ariz site:
Mitosis animation Cells Alive site:
Mitosis-Meiosis Activity:
Excellent Kean Univ Video of Overall Cell Cycle & Mitosis:
Kean Univ Video on Meiosis:

41. Chromosomal Replication
Paired
chromatids

42. Meiosis
Meiosis is the reproduction of sex cells (as opposed to somatic cells)
This process occurs only in the testes or ovaries
New cells (known as gametes) have only half the number of chromosomes of the parent cells
This # (different for each species) is known as the haploid number of chromosomes

43. Mitosis

44. Meiosis I

45. Meiosis II

46. Meiosis
Animation
with
crossing-over

48. Prophase 1 & Crossing over

49. Second
phase
of meiosis,
yielding
haploid
gametes
at bottom

50. Meiosis 1

55. PBS- Mitosis/meiosis side by side diagrams:
Kean Univ Video on Meiosis:
Mitosis-Meiosis Activity:

59. Oncogenes are mutated forms of normal
cellular genes involved in growth signalling
pathways (proto-oncogenes). When these genes
become mutated the cell does not require the
presence of pro-growth signals (e.g. growth
factors) in order to undergo cell division.

63. Tumour suppressor genes are genes often
involved in the apoptotic pathway. Normally
tumour suppressors detect breaks or defects
in the DNA - if present in low concentrations
these proteins will pause the cell cycle and
active DNA repair mechanisms. If present in
high concentrations, tumour suppressors shut
down the cell cycle or cause apoptosis. When
these genes are mutated to be dysfunctional
then the cell does not undergo either of these
events

64. The abnormal receptor on the right
was coded for by an oncogene, it is no
longer subject to the normal regulatory
mechanisms of the organism

67. Chemotherapy & Side Effects

71. 1.  Diagram A represents a cell from an organism with a diploid
chromosome number of 10. Therefore, the diagram represents
which one of the following stages?
A. interphase of mitosis
B. anaphase of mitosis
C. metaphase I of meiosis
D. prophase II of meiosis
E. anaphase II of meiosis
2.  Diagram B represents a cell from an organism with a diploid
chromosome number of 8. Therefore, the diagram represents
A. prophase of mitosis
B. metaphase of mitosis
D. telophase I of meiosis
E. metaphase II of meiosis

72. 3. Diagram B represents a cell from an organism with a diploid
chromosome number of 4. Therefore, the diagram represents which
one of the following stages?
A. prophase of mitosis
B. metaphase of mitosis
C. metaphase I of meiosis
D. telophase I of meiosis
E. metaphase II of meiosis
4. Diagram B represents a cell from an organism with a diploid
chromosome number of 6.  Therefore, the diagram represents which
A. Prophase of mitosis B. Metaphase of mitosis C. Metaphase I of meiosis D. Telophase I of meiosis E. Metaphase II of meiosis F. None of the above

73. 5.  Diagram C represents a cell from an organism with a diploid
chromosome number of 6. Therefore, the diagram represents which
one of the following stages?
A. prophase of mitosis
B. metaphase of mitosis
C. metaphase I of meiosis
D. prophase II of meiosis
E. metaphase II of meiosis
6.  Diagram D represents a cell from an organism with a diploid
chromosome number of 2. Therefore, the diagram represents which
B. prophase I of meiosis
C. prophase II of meiosis
D. metaphase of mitosis
E. metaphase I of meiosis
F. metaphase II of meiosis

76. Chromosome
Spread
& Karyotype

79. Chromosome
models