Gene Mutation

Question 1

Germ-line mutations

Answer 1

mutations passed through the gametes

Question 2

Somatic Cell Mutations

Answer 2

Show patches of affected areas, no gametes will carry the mutations.

Question 3

Spontaneous Mutations

Answer 3

Occur naturally. A baby will have an average of 60 new mutations, 90% will be in non-coding regions

Question 4

What percentage of DNA actually codes for proteins?

Answer 4

1.5%

Question 5

What are induced mutations caused by?

Answer 5

Mutagens

Question 6

Chromosomal mutation effects can result in:

Answer 6

Duplications
Inversions
Deletions
Insertions
Translocation

Question 7

Mutations in nucleotide sequences include:

Answer 7

point mutations
base substitutions
insertions
deletions

Question 8

A point mutation is:

Answer 8

A substitution of a single base nucleotide with another nucleotide (doesn’t effect the number of nucleotides)

Question 9

Silent Mutation

Answer 9

Does not change the amino acid encoded by the codon and includes mutations occuring in introns.

Question 10

Missense mutations

Answer 10

Changes the amino acid encoded by the codon.

Question 11

Why would a missense mutation be harmless?

Answer 11

If the amino acid that the changed codon produces is chemically similar to the one the non-mutated gene codes for, or if it is in an unimportant area.

Question 12

Why would a missense mutation be harmful?

Answer 12

A chemically different amino acid can cause changes in structure and function, such as in sickle cell anaemia in which the change from Glu to Valine results in a structural change in the RBS that effects its function.

Question 13

Nonsense Mutation

Answer 13

Changes an amino acid codon to a termination (stop codon). the resulting amino acid is shortened.

Question 14

Sense Mutations

Answer 14

Converts a stop codon to a sense codon.

Question 15

What causes a Frameshift Mutation?

Answer 15

Insertions or deletions of a single base pair.

Question 16

Loss of Function mutation.

Answer 16

A mutational effect that impedes function.
Mostly recessive, but can be dominant.

Question 17

Null Mutations

Answer 17

a mutational effect that abrogates/blocks function.

Question 18

Trinucleotide Repeat Diseases

Answer 18

Genetic diseases characterised by the presence of unstable and abnormal expansions of DNA-triplets.

Question 19

abnormally repeated DNA-triplets may cause:

Answer 19

gene inactivation or production of a toxic protein may be caused by:

Question 20

Genetic Anticipation

Answer 20

Severity of mutation increases with each successive generation.

Question 21

Cystic Fibrosis is what type of disease?

Answer 21

A Trinucleotide Repeat Disease

Question 22

Lethal mutations can be carried on to successive generations by…

Answer 22

slow onset.

Question 23

Mutations such as trinucleotide repeat diseases can increase in severity with each successive generation due to:

Answer 23

genetic anticipation.

Question 24

Cystic Fibrosis is cause by what a mutation of which gene?

Answer 24

The CFTR gene.

Question 25

What is the function of the protein coded for on the CFTR gene?

Answer 25

It is an ion channel for fluid homeostasis and when mutated, causes a build up of fluid in the lungs.

Question 26

The position of the mutation in the CFTR gene effects what?

Answer 26

Gene phenotype and severity of protein function. Can be partially active or completely inactive - which affects drug function.

Question 27

Mutagens

Answer 27

A physical or chemical agent that changes the DNA of an organism and increases the frequency of mutations.

Question 28

What mutagens can cause chemical modifications to DNA in the intracellular environment?

Answer 28

Free radicals and Reactive Oxygen Species

Question 29

How do free radicals and reactive oxygen species chemically modify DNA?

Answer 29

Can cause loss of bases and single strand breaks by oxidising the nucleotides and thus affecting their chemical structure. (steals their electrons)

Question 30

What are some examples of mutagens from the external environment?

Answer 30

Radiation
Chemicals
Base Analogues
Base Modifiers

Question 31

How does ionising radiation cause DNA mutations?

Answer 31

Ionising radiation causes the formation of free radicals and reactive oxygen species that oxidises nucleotides.

Question 32

How does non-ionising radiation (such as UVB) cause DNA mutations?

Answer 32

The biological effects observed for non-ionising radiation includes production of free radicals, double stranded DNA breaks and induced thymine dimers.

Question 33

How do chemical mutagens cause DNA mutations?

Answer 33

They intercalate between base pairs of DNA and causes separation of base pairs and unwinding. They make good nucleic acid stains.

Question 34

Base analogues have a similar structure to…

Answer 34

nucleotide bases and are incorporated into the DNA.

Question 35

How do Base Analogue mutagens cause mutations?

Answer 35

They can cause mispairing during DNA replication.

Question 36

Two types of Base Modifiers are:

Answer 36

Alkylating Agents
Mustard gas

Question 37

Alkylating agents act as mutagens by:

Answer 37

transferring alkyl groups (methyl/ethyl) to nucleotide bases.

Question 38

What does Mustard Gas do to Guanine?

Answer 38

It akylates guanine leading to cellular death and cancer.