Download The nucleus contains an information-rich

GUIDED READING - Ch. 12 - Section 1, 2, & 4
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The nucleus contains an information-rich genome [1]
1. Before being duplicated in S phase of interphase, what does a chromosome (a G1 chromosome) consist
of?
2. If you stretch out all 46 chromosomes, the DNA is around 2 meters or 6 1/2 feet long! How does the
cell get all of this DNA to fit inside the nucleus? (Be sure to use and define the term histone as part of
your answer)
3. What does the term “genome” refer to?
4. What is the difference between coding and noncoding regions of DNA?
5. a. What was the Human Genome Project?
b. In what ways is having a complete map of the human genome useful? [1]
Accidents affecting chromosomes can cause disorders [1]
6. Mitosis and meiosis are two types of cell division you need to be very familiar with. What was meiosis
used for again and where does meiosis take place in the body?
7. a. What does trisomy 21 mean?
b. According to your text, what causes trisomy 21?
c. Trisomy 21 causes Down syndrome. What are the symptoms of Down syndrome?
8. a. What is “nondisjunction”?
b. When does nondisjunction take place in meiosis?
c. What is the result of nondisjunction as far as the genetic make-up of gametes formed?
d. Explains why there is a difference in the resulting gametes if nondisjunction occurs during
Anaphase I of Meiosis I or Anaphase II of Meiosis II (If you do not remember the stages of meiosis,
please review section 9.5 in your textbook).
e. How can nondisjunction in sperm or an egg cell result in a fertilized cell and eventually a baby
with Down syndrome?
9. Explain the correlation between maternal age and the incidence of Down syndrome or the probability
of non-separation of chromosomes in a mother’s gametes? [1]
10. Changes in the structure of a chromosome itself may also cause disorders. Describe the following gross
chromosomal mutations. Also explain the effect it may have on the organism.
a. Duplications
b. Deletions
c. Inversions
d. Translocations
11. a. Geneticist Barbara McClintock discovered “jumping genes” in the 1940s. What are these
“transposons”?
b. How are transposons different from chromosomal inversions or insertions?
c. What effect can they have on other genes in an organisms genome and why?
Genetic changes contribute to cancer [1]
12. Cancer is caused by mutations in DNA caused by being exposed to mutagens such as radiation (such
as UV light) and chemicals (carcinogens) or by being inherited. Normally, two types of genes produce
proteins that help regulate a cells cell cycle, making sure it only divides when it should. These two
classes of genes are Growth Factor genes and Tumor-Suppressor genes. Explain the function of each.
a. Growth factor genes
b. Tumor-suppressor genes
13. a. What is an oncogene?
b. How does it develop?
14. What happens to the cell cycle when a Growth Factor gene (now an oncogene) produces too much
growth factor?
15. What happens to the cell cycle when a Tumor-Suppressor gene does not produce its protein product?
16. Why are most cancer causing mutations not inherited?
17. a. Why is it wrong to say that you inherit cancer?
b.
How is the predisposition to developing cancer inherited?
18. Describe how a woman inheriting a mutated BRCA1 gene is at a higher risk for developing breast
cancer? [1]
[1] Campbell, Heyden, Williamson. 2006. Biology: Exploring Life. Prentice Hall: Boston, MA.