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Name ______________________________ Class ___________________ Date __________________
Skills Worksheet
CH10.1 Active Reading
Section: Cell Reproduction
Read the passage below. Then answer the questions that follow.
A gene is a segment of DNA that codes for RNA and protein. A
single molecule of DNA has thousands of genes lined up like the
cars of a train. When genes are being used, the strand of DNA is
stretched out so that the information it contains can be decoded
and used to direct the synthesis of proteins needed by the cell.
As a eukaryotic cell prepares to divide, the DNA and the
proteins associated with the DNA coil into a structure called a
chromosome. Before the DNA coils up, however, the DNA is
copied. The two exact copies of DNA that make up each
chromosome are called chromatids. In the chromatids, the DNA
is very condensed. The two chromatids, which become separated
during cell division and are placed into each new cell, ensure that
each new cell has the same genetic information as the original cell.
SKILL: READING EFFECTIVELY
Read each question, and write your answer in the space provided.
1. How are genes and DNA related?
_______________________________________________________________
_______________________________________________________________
2. What occurs to a DNA strand as its genes are being used?
_______________________________________________________________
_______________________________________________________________
3. How are chromatids and chromosomes related?
_______________________________________________________________
_______________________________________________________________
An analogy is a comparison. In the space provided, write the letter of the term that
best completes the analogy.
_____ 4. A train is to cars as a molecule of DNA is to
a. chromatids.
b. genes.
c. proteins.
d. RNA.
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Biology
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Cell Growth and Division
Name ______________________________ Class ___________________ Date __________________
Skills Worksheet
CH10.2 Active Reading
Section: Mitosis
Read the passage below. Then answer the questions that follow.
During its lifetime, a cell goes through a repeating sequence of
cellular growth and division. This repeating sequence is called the
cell cycle. A cell spends 90 percent of its time in the first three
phases of the cycle, which are collectively called interphase. A
cell will enter the last two phases of the cell cycle only if it is
about to divide.
The five phases of the cell cycle are as follows:
First gap (G1) phase: During the G1 phase, a cell grows
rapidly and carries out its routine functions. This phase occupies
the major portion of the cell’s life in most organisms.
Synthesis (S) phase: A cell’s DNA is copied during this
phase. At the end of this phase, each individual chromosome
consists of two sister chromatids attached at the centromere.
Second gap (G2) phase: In the G2 phase, preparations are
made for the nucleus to divide. Mitochondria and other organelles
replicate. Hollow protein fibers called microtubules are assembled.
The microtubules are used to move the sister chromatids during
mitosis.
Mitosis: The process during cell division in which the nucleus
of a cell is divided into two nuclei is called mitosis, each with a
complete set of the cell’s chromosomes.
Cytokinesis: The process during cell division in which the
cytoplasm divides is called cytokinesis. In this process, each
daughter cell receives about half of the original organelles in a
cell.
SKILL: READING EFFECTIVELY
Read each question, and write your answer in the space provided.
1. Identify and define the two Key Terms in the first paragraph of this passage.
_______________________________________________________________
_______________________________________________________________
_______________________________________________________________
2. A cell viewed under a high-powered microscope appears to be in the fourth
phase of the cell cycle. What does this indicate about the cell?
_______________________________________________________________
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Biology
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Cell Growth and Division
Name ______________________________ Class ___________________ Date __________________
Active Reading continued
SKILL: SEQUENCING INFORMATION
Match each statement with the phase of the cell cycle it describes. Write the letter of the
correct phase in the space provided. Some choices may be used more than once.
_____ 3. The nucleus divides.
_____ 4. It makes up a major portion of
most cells’ lives.
_____ 5. The cytoplasm divides.
a.
b.
c.
d.
e.
first gap phase
synthesis phase
second gap phase
mitosis
cytokinesis
_____ 6. The mitochondria replicate.
_____ 7. The cell grows rapidly.
_____ 8. Two identical nuclei are produced.
_____ 9. DNA is copied.
_____ 10. Microtubules are assembled.
_____ 11. Sister chromatids form and become attached at the centromere.
_____ 12. The cell carries out its routine functions.
_____ 13. Microtubules move sister chromatids.
Read the question, and write your answer in the space provided.
14. How are mitosis and cytokinesis alike? How do they differ?
_______________________________________________________________
_______________________________________________________________
_______________________________________________________________
An analogy is a comparison. In the space provided, write the letter of the term that
best completes the analogy.
_____ 15. G2 phase is to mitochondria as S phase is to
a. chromatids.
b. centromere.
c. microtubules.
d. DNA.
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Biology
11
Cell Growth and Division
Name ______________________________ Class ___________________ Date __________________
Skills Worksheet
CH10.3 Active Reading
Section: Regulation
Read the passage below. Then answer the questions that follow.
The cell cycle has checkpoints. These are mechanisms the cell
uses to make sure it is ready to go on to the next phase. There are
three main checkpoints in the cell cycle.
The first checkpoint comes during the first gap phase. It is
called the G1 checkpoint. Its purpose is to check the cell and its
surroundings before cell division begins. The cell needs to be large
enough and healthy enough to undergo cell division. It needs to
have adequate nutrients and oxygen to sustain the process. If
conditions are not favorable, the cell goes into a resting phase. If
conditions are favorable, the cell enters the synthesis phase.
The second checkpoint comes during the second gap phase. It
is called the G2 checkpoint. Its purpose is to ensure that the cell is
ready for mitosis. As with the G1 checkpoint, the cell must still be
large enough and healthy enough to continue cell division. The
copied DNA must be identical to the original DNA. If there are
mistakes in the copied DNA, enzymes correct the mistakes. If the
cell is not large enough, the cell continues growing until it reaches
the optimal size. When conditions are favorable, mitosis begins.
The third checkpoint comes during metaphase in mitosis. It is
called the mitosis checkpoint. Its purpose is to check that the
genetic material will divide properly into the two daughter cells.
During the mitosis checkpoint, the cell makes sure that all the
chromosomes have lined up properly at the cell equator. It checks
to make sure that each chromosome is properly attached to the
spindle. If chromosomes need rearranging or attaching or
reattaching to the spindle, the cell makes these adjustments. When
conditions are favorable, mitosis continues.
SKILL: READING EFFECTIVELY
Read each question, and write your answer in the space provided.
1. What is the general purpose of the checkpoints related to the cell cycle?
_______________________________________________________________
_______________________________________________________________
2. Why are checkpoints important to the health of cells?
_______________________________________________________________
_______________________________________________________________
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Biology
12
Cell Growth and Division
Name ______________________________ Class ___________________ Date __________________
Active Reading continued
3. When does the G1 checkpoint occur? What does the cell check?
_______________________________________________________________
_______________________________________________________________
4. What happens if a cell does not pass the G1 checkpoint?
_______________________________________________________________
5. What happens if a cell passes the G1 checkpoint?
_______________________________________________________________
6. When does the G2 checkpoint occur? What does the cell check?
_______________________________________________________________
_______________________________________________________________
7. What happens if a cell does not pass the G2 checkpoint?
_______________________________________________________________
_______________________________________________________________
8. What happens if a cell passes the G2 checkpoint?
_______________________________________________________________
9. When does the mitosis checkpoint occur? What does the cell check?
_______________________________________________________________
_______________________________________________________________
10. What happens if a cell does not pass the mitosis checkpoint?
_______________________________________________________________
_______________________________________________________________
11. What happens if a cell passes the mitosis checkpoint?
_______________________________________________________________
Write the letter of the term that best answers the question.
_____ 12. Which graphic could you use to best show the checkpoints in the cell
cycle?
a. line graph
b. bar graph
c. flowchart
d. map
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Biology
13
Cell Growth and Division