Unit A Reproduction

15. Complete the following table to compare mitosis
and meiosis.
Type of cell division
Number of chromosomes 2n
in parent cell
Number of daughter cells 4
Number of chromosomes
n
in daughter cells
16. (a) What are cancer-causing agents called?
(b) Name three known causes of cancer.
17. (a) What special ability do the stem cells in an
embryo have?
(b) Where else are stem cells found?
18. List the following events of pregnancy in the
correct order.
(a) The umbilical cord connects to the placenta.
(b) The head of the fetus is down.
(c) The heart begins to beat in the embryo.
(d) The gender of the fetus is obvious.
(e) The fetus has a wake and sleep cycle.
Use What You’ve Learned
19. Use your knowledge of the cell cycle to answer
the following questions.
(a) In which phase does growth occur?
(b) When do cells replicate their genetic material?
(c) When do chromosomes line up at the equator?
(d) When does cytokinesis begin?
(e) When do chromosomes shorten, thicken,
and become visible under the microscope?
(f) When do sister chromatids separate and
move to the poles of the cell?
(g) When does the cell plate begin to form?
20. How does DNA carry the genetic code?
21. Identify the following characteristics as
belonging to normal cells or cancer cells.
(a) The cells stay attached after cell division.
(b) The nucleus is enlarged.
(c) The cells stop dividing when they touch
another cell.
(d) The cells travel through the blood vessels.
22. Explain the relationship between a carcinogen
and a mutation.
23. Fruit flies normally have eight chromosomes.
Figure 4 shows the stages of meiosis.
(a) In which parent did nondisjunction take place?
(b) What is happening during process X?
(c) How many chromosomes would be found in
zygotes D, E, and F?
(d) Which zygote would most likely be normal?
female A male B female C
8
3 5
chromosome
number
process X
zygote D
8 8
meiosis meiosis meiosis
Figure 4
4 4 4 4
zygote F
zygote E
24. Use your knowledge of reproduction to answer
the following questions.
(a) How many chromosomes are in the egg cell?
(b) Explain how the egg cell could be produced
from a cell that has 46 chromosomes.
(c) How many chromosomes are in each cell of
the embryo?
(d) What process causes growth of the embryo
and an increase in the number of cells?
(e) What role do stem cells play in the
development of the embryo?
25. Compare in vitro fertilization with the normal
events of fertilization in humans.
146 Unit A Reproduction
NEL