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37
Mutations, Deletions, and Substitutions
Biology B
Name: _______________ Number: ____Date: ______ Period: _______
DNA is found in all living cells. Changing DNA in some way MAY
change the genes found in the DNA structure. The nucleotide sequence in
every gene “codes” for a specific trait. What this really means is that each
gene “codes” for the production of a unique protein. Proteins are the real
“work-horse” of the cell. Proteins actually “do” the work in the cell. All
enzymes have at least some protein in them and almost all other components
of the cell’s organelles are made of protein. If you alter the DNA structure
in some way, you may alter the protein so that it does not function the way it
is supposed to. DNA can be changed in four different ways:
1.) Natural mistakesreason the DNA
molecule is so big that
when the cell makes a
copy of it, it is bound
to make mistakes.
This type of mistake
is called evolution.
Evolution is the
change in DNA sequence over time.
2.) High energy radiation- such as Ultra-violet
(UV) rays, x-rays, and gamma rays. These
high energy waves can selectively delete a
single nucleotide, or create massive deletions
of several nucleotides (which normally
destroys the function of the protein it is
supposed to make). These high
energy waves can cause deletions,
substitutions, or entire pieces of gene
may be inverted.
Page 2 (Cont. Handout #37 Bio. B)
3.) Mutagens are chemical compounds known to change the sequence of
nucleotides. Mutagens do NOT necessarily have a bad effect on DNA.
(Examples: cigarette smoke, pollution, bacteria/viral infection, industrial
cleaning fluids, laboratory chemicals, etc…)
4.) Carcinogens: These are chemicals or
high energy waves that are KNOWN to
cause cancer. This does not mean they will
ALWAYS cause cancer. Known
carcinogens are chemicals such as benzene,
acetone (nail polish remover), cigarette or
marijuana smoke, certain virus particles,
etc..)
There are only three ways DNA mutation
may affect cells:
1) Bad effect (might be repaired)
2) No effect (most likely)
3) Good effect
Page 3 (Cont. Handout #37 Bio. B)
All these DNA mutations have one thing in common: they all cause
some alteration in the nucleotide sequence of a gene in DNA. Since the
nucleotide sequence in a particular gene in the DNA dictates what kind of
protein is made, changing the sequence MAY change the protein and
therefore a trait controlled by that protein.
The way a trait (color hair, color eyes, tall, short, etc…) is expressed
is that a protein MUST be made. Failure to make a correct protein will
change the trait. That may be
that cell can (1) repair the
damage, (2) ignore the
damage (the error has no overall effect), (3) cannot repair
the damage and the cell selfdestructs (called apoptosis), or
(4) there is a positive effect of
a DNA mutation. (see right:)
The cells in the body are
organized to try and prevent
damage, or failing that, will
try to fix errors. However,
when DNA is damaged and
cannot be repaired, the cell often resorts to suicide (called apoptosis).
Apoptosis is a better alternative than allowing the cell to become cancerous.
Cancer is really uncontrolled mitosis and can be classified in two
ways: Benign versus Malignant (metastasize means cancer cells move from
place to place)
Page 4 (Cont. Handout #37 Bio. B)
Answer the following questions here and on your scan-tron.
_____ 1.) Changes in the nucleotide sequence of DNA over time that occur
naturally…
a.) is called evolution b.) will always cause cancer c.) have no effect
_____ 2.) If you change the nucleotide sequence of a gene, you may…
a.) change the protein that was supposed to be made
b.) cause the cell to perform apoptosis
c.) cause the cell to become cancerous
d.) all of the above might be true
_____ 3.) The difference between a mutagen and a carcinogen is…
a.) a mutagen will damage DNA and a carcinogen will not
b.) a carcinogen will damage DNA and a mutagen will not
c.) both will damage DNA but carcinogen is KNOWN to cause cancer
d.) neither will damage DNA but mutagens will always cause cancer
_____ 4.) Apoptosis may occur when…(see page 3 diagram)
a.) a cell has no damage and is working properly
b.) a cell sustains some DNA damage but it was repaired correctly
c.) a cell sustains some DNA damage and repair is insufficient
d.) none of the above are true
_____ 5.) All of the following may damage DNA in some way except…
a.) natural mistakes
b.) high energy waves (UV/X-rays)
c.) carcinogens/mutagens
d.) all of these will damage DNA
_____ 6.) The difference between benign and malignant cancer is….
a.) benign cancer grows slowly and does not metastasize and malignant
cancer grows fast and does metastasize
b.) malignant cancer grows slowly and does not metastasize and benign
cancer grows fast and does metastasize
_____ 7.) The ways a DNA mutation may affect a cell are (mark all that
apply)
a.) Bad effect b.) No effect c.) Good effect
Page 5 (Cont. Handout #37
Bio. B)
_____ 8.) What is the most likely effect of DNA mutation on a cell?
a.) Bad effect b.) No effect c.) Good effect
_____ 9.) The one thing that all DNA mutations have in common is?
a.) they all cause cancer
b.) they cause some change in the nucleotide sequence
c.) they all cause apoptosis
d.) they have no effect on the cell
_____ 10.) When is DNA mutation most likely to have the most negative
effect on a developing organism?
a.) at the zygote level b.) right after cell repair c.) right after apoptosis
Date: ______________________________
Lesson Plan for Handout #37 Biology B
Objective: TLWD ability to determine the different ways DNA might be
damaged, determine the 3 possible outcomes to DNA mutation and to
recognize that DNA mutation is natural and will occur regardless of any
other outside force.
Content: DNA replication
NJCCCS: 5.3.12.D.1.
Homework: Complete #37
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