Lesson 6: Mutations

Question 1

Mutation

Answer 1

A permanent change in the genetic material of an organism

All mutations are heritable (they can be copied during DNA replication)

Not all mutations are passed on to future generations

Germ Cell Mutations:

Mutations to the information on reproductive cells

These mutations will be passed on to offspring

Somatic Cell Mutations:

Mutations that are passed on to daughter cells in the body BUT NOT to
offspring

Question 2

Types of Mutations

Answer 2

1. Point Mutations
2. Frameshift Mutations
3. Chromosomal Mutations

Question 3

Point Mutations

Answer 3

A mutation in which one nucleotide
in a DNA sequence is replaced by
another nucleotide.

Often this occurs with a
substitution.

Question 4

Consequences of Point Mutations

Answer 4

Silent Mutation:

This mutation has no effect on the cell’s metabolism and how proteins are assembled.

Mis –Sense Mutation:

The substitution leads to an altered but functioning protein.

Nonsense Mutation

The substitution erases a start sequence or inserts a stop sequence

Question 5

Frameshift Mutations

Answer 5

A type of point mutation in
which one or more nucleotides
are inserted or deleted from the
DNA sequence

These types of mutations cause
the reading frame of a gene to be
altered

Frameshift mutations often
result in non – sense mutations

Question 6

Chromosomal Mutations

Answer 6

Mutations that affect more than one gene on one or more chromosomes

Portions of chromosomes are lost and gained during cross – over in
meiosis

Portions of Chromosomes can be duplicated or lost during DNA
replication

This results in a restructuring of the DNA sequence

Question 7

Causes of Mutations

Answer 7

Mutations that arise as a result of the natural processes of the cell are called
Spontaneous Mutations.

Mutations that are caused by factors outside the cell are called Induced
Mutations.

A substance or event that increases the rate of mutation in an organism
is called a mutagen.

Question 8

Physical Mutagens

Answer 8

High energy radiation, like that of X rays and gamma rays are examples of a physical
mutagen.

This radiation tears through a DNA strand causing random changes in the nucleotide
sequence.

Causes mutations ranging from the deletion of just a few nucleotides to the loss
of large portions of chromosomes.

High energy radiation is the most damaging form of mutagen known.

Ultraviolet radiation has lower levels of energy but is still a powerful mutagen.

It is most likely to affect pyrimidine bases (C and T) that are adjacent to each
other.UV radiation causes a change in
the bases that bond them
covalently to form a larger
molecule called a dimer.

This distortion interferes with
DNA replication often causing
cancer.

Question 9

Chemical Mutagens

Answer 9

A molecule that can enter the cell nucleus and induce mutation by reacting
chemically with DNA.

May act by inserting themselves into the DNA molecule causing a
frameshift mutation

May have a structure similar to ordinary nucleotides but with different
base pairing properties.