Grade 9 Science
Unit 2
Reproduction
Chapter 4: The nucleus controls the functions of
life.
Name:
Homeroom #:
_____
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The Function of the Nucleus

The
that is responsible for
the functions of the cell.

The

The nucleus contains the master set of instructions that determines…
and for controlling
centre of the cell.
Heredity

A particular feature that can vary in size or form from individual to individual within a
species is called a
.

Inherited from

The process through which patterns of traits are passed on from an individual to its
offspring is called
.
.
DNA

Carries the instructions in the

A long,

Forms a helix structure or a
.

The sides of the “ladder” are made from
and
.
molecule.
2

The steps are made of 4
bases. These are:
1.
2.
3.
4.

The bases in a DNA molecule always join in a specific way:
joins with
Joins with

When a cell is ready to divide, each coil of loosely coiled DNA folds up further into a
compact,
structure called a
.

Chromosomes within the nucleus are found in

Most humans have
.
pairs of chromosomes including one pair that determines
.
Genes

Found on chromosomes.

Small

Store information needed to produce

Can vary in length, from

The arrangement of

Each chromosome contains
of DNA located at specific places on a chromosome.
used by body cells.
to
bases.
will determine the protein produced.
of genes.
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
Proteins determine what body cells will become and how they will function.
Examples:
1. Specialized cells will form
; tissues will form
2. Specialized proteins called
chemical reactions that occur within each cell. Ex.
speed up the
3. Some proteins act as chemical messengers called
Mutations

A change in the specific order of the
that make up a particular

A base may be
or

Effects of Mutations…
,
for another.
1.
Ex.
2.
Ex.
3.
Ex.
What type of
mutation is this?
Give your reasons.
4

Substances or factors that can cause mutations in DNA are called
For Example
Mutations can be caused by…
1.
Ex.
2.
Ex.
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Chapter 2 Questions
1. What is a trait? Give an example. (Page 112)
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2. What is heredity? (Page 112)
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3. Where is heredity information stored? (Page 113)
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4. Why is the nucleus sometimes called “the control centre of the cell”? (Page
114)
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5. Why is DNA required in every cell? (Page 115)
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6. How many chromosomes does a human body cell contain? (Page 117)
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7. How does a gene differ from a chromosome? (Page 118)
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8. What are genes? Where are they located? (Page 118)
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9. What are the functions of proteins in cells? (Page 119)
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10.
Explain the function of a gene in a cell. (Page 119)
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11.
If you think of DNA as a chemical alphabet, how could you describe
genes and chromosomes?
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12.
What is a gene mutation? (Page 122)
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13.
How can a gene mutation create a change in an organism? (Page 124)
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14.
Give an example of a positive mutation. (Page 124)
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15.
Give an example of a negative mutation. (Page 125)
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16.
Give an example of a neutral mutation. (Page 126)
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17.
What is a mutagen? (Page 127)
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18.
Describe two sources of mutagens. (Page 127)
1. .______________________________________________________
2. .______________________________________________________
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19.
How do viruses cause mutations? (page 127)
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20.
List three examples of environmental mutagens. (Page 127)
1. ______________________________________________________
2. ______________________________________________________
3. ______________________________________________________
21.
Describe an example of a mutation caused by human activity. (Page 127)
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Practice Test
1. Which of the following is a trait?
A. age
B.
C. name
D.
eye colour
number of siblings
2. Which of the following gives a cell the instructions it needs to develop into a muscle
cell,
a bone cell, or a skin cell?
A. chromosome
B.
DNA
C. gene
D.
nucleus
3. Which one of the following statements is true?
A. A gene stores the information to make a particular protein.
B. All the genes within the nucleus of a cell will be copied to make a protein at some
time in the life cycle of a cell.
C. Different proteins have the same sequences of bases.
D. Different types of cells in your body contain different genetic information.
4. What does DNA do when a cell is ready to divide?
A. It divides into 46 parts.
B.
It divides into two parts.
C. It folds up into a chromosome.
D.
It unfolds into a gene.
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5. A gene mutation is which of the following?
A. a change in the specific order of the sugar and phosphates that make up a
particular protein.
B. a change in the specific order of the A, G, C, and T bases that make up a particular
protein.
C. a substance that causes genes to be copied incorrectly.
D. a substance that changes the DNA structure.
6. Which of the following is an example of a natural mutagen?
A. cigarette smoke
B. cleaning products
C. industrial waste
D. virus
Match the Term on the left with the best Descriptor on the right.
Each Descriptor may be used only once.
Term
_____ 7.
_____ 8.
_____ 9.
_____10.
_____11.
_____12.
chromosome
DNA
gene
gene mutation
nucleus
trait
Descriptor
A. feature that varies from individual to individual
B. controls the functions of the cell
C. long, two-stranded molecule that carries
instructions for cell activities
D. small segments of DNA located at specific
places on a chromosome
E. X-shaped structure of loosely folded DNA
F. change in the order of A, G, C, and T bases in a
gene
Short Answer Questions
13. Explain how the nucleus controls the activities within a cell.
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14. Describe two effects of specific gene mutations.
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