This document discusses how cancer arises from uncontrolled cell division caused by mutations that disrupt normal cell cycle regulation. It outlines several key characteristics of cancer cells, including the potential to grow independently of growth factors, loss of contact inhibition, unregulated division, expression of telomerase, ability to metastasize, induce angiogenesis, and evade apoptosis. Chromosomal abnormalities are also examined, such as aneuploidy, which can lead to disorders like Down syndrome, Edwards syndrome, and Patau syndrome. Chromosomal rearrangements including deletions, duplications, inversions, and translocations are also summarized.

1. Objectives
• explain how cells can escape the normal regulatory control of
the cell cycle;
• analyze how different human disorders arise from accidents
occurring during cell division; and
• describe the different types of chromosomal aberrations and
give examples of each.

3. Cancer
• a disease characterized by uncontrolled cell division
• factors causing cancer is often an interaction between
environmental, genetics and/or lifestyle effects
• multiple mechanisms must fail before a critical mass is
reached and cells become cancerous
• most cancers arise as cells acquire a series of mutations

4. Key characteristics of cancer
1. May or may not need growth factors
2. Loss of contact inhibition
3. Unregulated division
4. Express telomerase
5. Metastasis
6. Angiogenesis
7. Failure to undergo apoptosis

5. May or may not need growth factors
cell
metabolism,
cell cycle
progression,
cell death &
neurological
fxn
molecular
switches
activated by
binding to
GTP

6. Loss of contact inhibition
controls cell maturation

7. Unregulated Division
Proto-oncogenes and Tumor-suppressor genes
normally promotegrowth and
division of normal cells
normally inhibit division and survival of abnormal cells

8. Express telomerase

9. Metastasis
• spreading of cancer to a different part of the body from where it
started

11. Angiogenesis
• Blood vessel formation

13. Non-Disjunction
• Failure in the separation
of: (a) homologous
chromosomes to during
meiosis I or (b) sister
chromatids during
meiosis II

14. Chromosome Aberrations
• large-scale variations
• changes to a chromosome region encompassing multiple
genes
• Divided into 2 groups:
1. Changes in chromosome number
2. Changes in chromosome structure

15. Aneuploidy
• the chromosome number is abnormal
• An aneuploid is an individual organism whose chromosome
number differs from the normal type by part of a chromosome set.
➢ Monosomic - zygote has only
one copy of a particular
chromosome (2n – 1)
➢ Trisomic - zygote has three
copies of a particular
chromosome (2n + 1)

16. I. Abnormal Chromosome Number
a. Aneuploidy of Autosomes
i. Down Syndrome (Trisomy 21; 47,XX/XY,+21)
ii. Edwards Syndrome (Trisomy 18; 47,XX/XY,+18)
iii. Patau Syndrome (Trisomy 13; 47,XX/XY,+13)
b. Aneuploidy of Sex Chromosomes
i. Turner Syndrome (Monosomy X; 45,XO)
ii. Klinefelter Syndrome (47,XXY)
iii. Jacobs Syndrome (47,XYY)
v. Metafemale (Trisomy X; 47,XXX)

17. Down Syndrome (Trisomy 21 )
A flattened face, especially the bridge of the nose
Almond-shaped eyes that slant up
A short neck
Small ears
Small hands and feet
Poor muscle tone or loose joints
Shorter in height as children & aduts

18. Patau Syndrome (Trisomy 13)

19. Turner Syndrome (Monosomy 23)

20. Klinefelter Syndrome (XXY)

21. Changes in Chromosome Structure
Changes in chromosome structure, called rearrangements,
encompass several major classes of events. A chromosome
segment can be:
1. lost - DELETION
2. doubled – DUPLICATION
3. orientation of a segment within the chromosome can be
reversed – INVERSION
4. segment can be moved to a different chromosome -
TRANSLOCATION

22. occurs when a segment
breaks off and reattaches
within the same chromosome,
but in reverse orientation
occurs when a chromosome
breaks and either the whole or a
portion of it reattaches to a
different chromosome

23. Cri-du-chat Syndrome