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Unit30 C

NEL Cell Division, Genetics, and Molecular Biology 555

4. Provide examples of hereditary traits that are
   (a) determined by genes
   (b) influenced by the environment


5. Many single-cell organisms divide by a process called binary fission. One cell
   divides into two cells identical to each other and identical to the original cell.
   More complex organisms form specialized sex cells. When sex cells combine
   from two different organisms, they form a fertilized egg or zygote.
   (a) Identify one advantage of binary fission as a means of reproduction.
   (b) Identify and explain an advantage of reproduction by the union of sex cells
   from different individuals.


6. Explain why the duplication of genetic material is essential prior to division.

Skills

7.Table 1shows the events in a typical cell cycle. Draw and label a

circle graph to represent the data.

8. A couple are expecting their third child. After the birth of two boys,
   they reason that the next child will be a girl.
   (a) Determine the probability of having three boys in a row.
   (b) Determine the probability that the next child will be a girl.

Figure 3
Skin cell, 450

Figure 4

Sperm cell, 1000

Figure 5
Unfertilized egg cell, 2000

Figure 6

Egg cell being fertilized by sperm cell, 5000

Table 1 Events in the Cell Cycle

Event Time (h)

rapid growth 15

growth and DNA replication 20

preparation for division 10

mitosis 5