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5.2: Chromosomes and Mitosis

Difficulty Level: At Grade Created by: CK-12
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Lesson 5.2: True or False

Name___________________ Class______________ Date________

Write true if the statement is true or false if the statement is false.

_____ 1. A chromatid is made of two identical chromosomes.

_____ 2. There may be thousands of genes on a single chromosome.

_____ 3. Prophase is the first phase of mitosis.

_____ 4. Female human cells have 23 pairs of homologous chromosomes.

_____ 5. Mitosis occurs in the following order: prophase - metaphase - telophase - anaphase.

_____ 6. The process in which the cell divides is called mitosis.

_____ 7. During mitosis, DNA exists as chromatin.

_____ 8. A gene contains the instructions to make a protein.

_____ 9. Chromosomes form during metaphase.

_____ 10. Mitosis is the phase of the eukaryotic cell cycle that occurs between DNA replication and the second growth phase.

_____ 11. Sister chromatids are identical.

_____ 12. Chromatids separate during anaphase.

_____ 13. Chromosomes are coiled structures made of DNA and proteins.

_____ 14. Human cells have 64 chromosomes.

_____ 15. Cytokinesis is the final stage of cell division.

Lesson 5.2: Critical Reading

Name___________________ Class______________ Date________

Read these passages from the text and answer the questions that follow.


Chromosomes are coiled structures made of DNA and proteins. Chromosomes are the form of the genetic material of a cell during cell division. During other phases of the cell cycle, DNA is not coiled into chromosomes. Instead, it exists as a grainy material called chromatin.

Chromatids and the Centromere

DNA condenses and coils into the familiar X-shaped form of a chromosome only after it has replicated, as seen in the figure below. Because DNA has already replicated, each chromosome actually consists of two identical copies. The two copies are called sister chromatids. They are attached to one another at a region called the centromere.

Chromosome. After DNA replicates, it forms chromosomes like the one shown here. (Image copyright Cre8tive Images, 2010. Used under license from Shutterstock.com. Text added by CK-12 Foundation.)

Chromosomes and Genes

The DNA of a chromosome is encoded with genetic instructions for making proteins. These instructions are organized into units called genes. Most genes contain the instructions for a single protein. There may be hundreds or even thousands of genes on a single chromosome.

Human Chromosomes

Human cells normally have two sets of chromosomes, one set inherited from each parent. There are 23 chromosomes in each set, for a total of 46 chromosomes per cell. Each chromosome in one set is matched by a chromosome of the same type in the other set, so there are actually 23 pairs of chromosomes per cell. Each pair consists of chromosomes of the same size and shape that also contain the same genes. The chromosomes in a pair are known as homologous chromosomes.


1. What is a chromosome? What is it made out of?

2. What are homologous chromosomes? How many homologous pairs are in a human cell?

3. What is the main difference between chromatin and chromosomes?

4. Why do chromosomes look like an “X”?

5. What is a gene?

Lesson 5.2: Multiple Choice

Name___________________ Class______________ Date________

Circle the letter of the correct choice.

  1. Why is it necessary for the DNA to replicate prior to cell division?
    1. so that each daughter cell will have 23 chromosomes
    2. so that each daughter cell will have a complete copy of the genetic material
    3. so that each daughter cell will have 46 homologous chromosomes
    4. so that each daughter cell will have 2 sister chromatids
  2. Why do chromosomes have an X-shape?
    1. because they are made of two sister chromatins
    2. because they are made of two sister centromeres
    3. because they are made of two sister chromosomes
    4. because they are made of two sister chromatids
  3. Chromosomes form during what part of the cell cycle?
    1. prophase of mitosis
    2. the end of the G2 phase
    3. right after S phase and DNA replication
    4. during cytokinesis
  4. The correct order of phases during mitosis is
    1. telophase→prophase→metaphase→anaphase
    2. prophase→anaphase→metaphase→telophase
    3. prophase→metaphase→telophase→anaphase
    4. prophase→metaphase→anaphase→telophase
  5. How many chromosomes are in a normal human cell?
    1. 23
    2. 32
    3. 46
    4. 64
  6. When do the sister chromatids line up at the equator of the cell?
    1. metaphase
    2. anaphase
    3. prophase
    4. telophase
  7. Which of the following statements concerning cytokinesis is correct? (1) cytokinesis occurs in both prokaryotes and eukaryotes, (2) cytokinesis is when the cytoplasm splits in two, (3) in plant cells, cytokinesis involves the formation of a cell plate.
    1. 1 only
    2. 2 only
    3. 1 and 2
    4. 1, 2, and 3
  8. During which phase of mitosis do the sister chromatids separate?
    1. prophase
    2. telophase
    3. anaphase
    4. metaphase

Lesson 5.2: Vocabulary I

Name___________________ Class______________ Date________

Match the vocabulary word with the proper definition.


_____ 1. division of the nucleus

_____ 2. region of the chromosome where sister chromatids are attached

_____ 3. division of the cytoplasm

_____ 4. phase of mitosis in which spindle fibers attach to the centromere of each pair of sister chromatids

_____ 5. coiled structures made of DNA and proteins

_____ 6. phase of mitosis in which sister chromatids separate and the centromeres divide

_____ 7. a segment of DNA with the genetic instructions to make a protein

_____ 8. two copies of replicated DNA that make a chromosome

_____ 9. the first and longest phase of mitosis

_____ 10. uncoiled DNA

_____ 11. a pair of the same chromosome

_____ 12. phase of mitosis in which the chromosomes begin to uncoil and form chromatin


a. anaphase

b. centromere

c. chromatid

d. chromatin

e. chromosome

f. cytokinesis

g. gene

h. homologous chromosomes

i. metaphase

j. mitosis

k. prophase

l. telophase

Lesson 5.2: Vocabulary II

Name___________________ Class______________ Date________

Fill in the blank with the appropriate term.

1. Chromosomes are coiled structures made of ____________ and proteins.

2. ____________ is the division of the nucleus.

3. During ____________, sister chromatids line up at the equator, or center, of the cell.

4. ____________ is the division of the cytoplasm.

5. There may be hundreds or even thousands of genes on a single ____________.

6. A ____________ contains genetic the instructions for making proteins.

7. During anaphase, sister ____________ separate and the centromeres divide.

8. The four phases of mitosis, in order, are ____________, ____________, ___________, ____________.

9. Human cells normally have ____________ chromosomes.

10. A new nuclear membrane forms during ____________.

11. The ____________ fibers ensure that sister chromatids will separate when the cell divides.

12. When a chromosome first forms, it actually consists of two sister ____________.

Lesson 5.2: Critical Writing

Name___________________ Class______________ Date________

Thoroughly answer the question below. Use appropriate academic vocabulary and clear and complete sentences.

Describe the structure of a chromosome, using proper vocabulary. Discuss when and why a chromosome forms.

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