(Chap 13) Mutations

Question 1

3 types of DNA mutations

Answer 1

Substitution
Deletion
Insertion

Question 2

2 types of Frame shift

Answer 2

Deletion

Insertion

Question 3

Describe the mutation called an “in-frame deletion or insertion”

Answer 3

It is the deletion or insertion of a multiple of three nucleotides that doesn’t alter the reading frame.

Question 4

What is a tranversion?

Answer 4

The replacement of a Purine to a Pyrimidine or the inverse.

Question 5

Base substitutions can be ___________ or _____________.

Answer 5

Transitions or transversion.
Transitions - A to G or G to A/T to C or C to T
Transversions - A to C, A to T, G to C, G to T/C to A, C to G, T to A, or T to G

Question 6

What is a transition?

Answer 6

The replacement of a Purine to another Purine or a Pyrimidine to a Pyrimidine

Question 7

What is a suppressor mutation?

Answer 7

It occurs elsewhere within the same gene, or in another gene altogether, but restores the wild-type phenotype.

Question 8

DNA mutations are genetic, but not always ___________.

Answer 8

heritable

Question 9

What is a germ-line mutation?

Answer 9

These are mutations that arise in cells that ultimately produce gametes and can be passed to future generations.

Question 10

What type of suppressor mutation occurs in the SAME gene as that containing that mutation being suppressed?

Answer 10

Intragenic suppressor mutation

Question 11

Intragenic suppressor mutation

Answer 11

Type of suppressor mutation occurs in the same gene as that containing that mutation being suppressed but it restores the wild type with different genotype.

Question 12

Intergenic suppressor

Answer 12

A mutation in a different gene (eg. tRNA) can suppress mutation that are copied into mRNAs.
Epistasis.

Question 13

Types of substitution mutations

Answer 13

1) Silent (change of a nucleotide without change in amino acid sequence)
2) Neutral (change of one a.a. but it doesn’t affects the function of the final product)
3) Missense (when the change of a single base pair causes the substitution of a different amino acid in the resulting protein affecting the function of the final product)

Question 14

Silent mutation

Answer 14

Change of a nucleotide in the codon (e.g. 3rd nucleotide wobble) without change in amino acid sequence

Question 15

Neutral mutation

Answer 15

Change of one amino acid but it doesn’t affects the function of the final product

Question 16

Missense mutation

Answer 16

When the change of a single base pair causes the substitution of a different amino acid in the resulting protein affecting the function of the final product

Question 17

Nonsense Mutation

Answer 17

A change in a sense codon (deletion or insertion) leads to a premature termination of translation.

Question 18

Forward Mutation (1st mutation)

Answer 18

Changes of the wild phenotype to a mutant phenotype

Question 19

Reverse Mutation (2nd mutation)

Answer 19

Corrects the exact original mutation. Changes of the mutant phenotype back to the wild phenotype.

Question 20

Suppressor mutation

Answer 20

Occurs elsewhere within the same gene, or in another gene, but restores the wild-type phenotype. The genotype is different from the wild-type.

Question 21

What are tautomeric shifts and its possible effect of DNA?

Answer 21

It is a proton shift which rearranges the double bond of a base. This normally occurs but only for a fraction of a second. The shift can lead to a spontaneous mismatch of base pairs.

Question 22

Why is spontaneous mutation rate low?

Answer 22

Fidelity of the replication enzymes and the efficiency of the DNA repair systems.

Question 23

What is tautomeric shifts?

Answer 23

a bond shift in the ring structure of a nitrogenous base

Question 24

What type of mutation results from unequal crossing over?

Answer 24

spontaneous mutation

Question 25

What are base analogs?

Answer 25

chemical mutagens that can be incorporated into DNA, and then proceed to base-pair incorrectly, which introduces mutations into the DNA.

Question 26

What type of mutation results from chemical mutagens?

Answer 26

induced mutations

Question 27

Which bases are pyrimidines?

Answer 27

cytosine, thymine, and uracil

Question 28

UV light creates ___________ ______________ which __________ _____ _______________

Answer 28

Pyrimidine dimers bend the DNA backbone

Question 29

What is the Ames test?I

Answer 29

t is a method used to determine how mutagenic a substance may be.

Question 30

Ames test protocol

Answer 30

1) His(-) in minimun media,
2) Compound X (the substance being tested that will mutate His (-) to His (+)
3) Liver enzymes to know if liver when reacts with Compound X produces the reversion to His (+)
4) High levels of His (+) means compound X is mutagenic

Question 31

What are transposons?

Answer 31

are mobile DNA segments that can disrupt gene function by inserting in or near genes.

Question 32

What rare genetic disease is characterized by acute sensitivity to sunlight and a predisposition to skin cancer?

Answer 32

Xeroderma pigmentosum

Question 33

What is the mismatch repair system?

Answer 33

A type of excision repair that specifically repairs mismatches that occur due to Pol error during replication, the newly synthesized strand can be targeted due to under methylation.

Question 34

1) What enzyme removes methyl groups from bases such as in Guanine?
2) In what type of repair system is used?

Answer 34

1) methyltransferase

2) direct repair

Question 35

What is a direct repair system?

Answer 35

changes the affected nucleotide back to its original structure

Question 36

1) What enzyme adds methyl groups from bases such as in Cytosine?

Answer 36

DNMT1 (DNA (cytosine-5)-methyltransferase 1)

Question 37

What rare genetic disease is characterized by defects in nucleotide-excision repair?

Answer 37

Xeroderma Pigmentosa

Question 38

What is the problem in Xerodema pigmentosa

Answer 38

defects in nucleotide-excision repair