Exam 3 - Mutations

Question 1

What are mutations?

Answer 1

Stable, heritable changes in the base sequence of DNA

Question 1

T/F
Mutations can only be spontaneous OR induced.

Answer 1

F, can be both.

Question 2

Where and how often do spontaneous mutations occur?

Answer 2

The natural environment, infrequently and randomly

Question 3

What is the general rate of mutation?

Answer 3

between 1 in 10,000 and 1 and 1trillion
(low due to cellular repair mechanisms)

Question 4

Spontaneous mutations can occur from: (3)

Answer 4

base substitutions
removal or addition of nucleotides
transposable elements

Question 5

What is the most common type of spontaneous mutation?

Answer 5

Base substitutions

Question 6

How do base substitutions occur?

Answer 6

From mistakes during DNA synthesis, incorrect base is incorporated into DNA

Question 7

Point mutations def.

Answer 7

One base pair is changed

Question 8

What are the (3) effects/types of base substitutions?

Answer 8

Silent mutations
Missense mutation
nonsense mutation

Question 9

Silent mutations def.

Answer 9

Result from a nucleotide change that generates a codon which still specifies the wild type amino acid

Question 10

Missense mutation def.

Answer 10

amino acid substitution mutation

Question 11

Nonsense mutation def.

Answer 11

mutation that changes an amino acid codon to a stop codon

Question 12

Base substitutions in the third position of a codon would most often cause what type of mutation?

Answer 12

Missense
Asense
Nonsense
Silent (a majority of the time, not all)

Question 13

Generally, what does the removal or addition of nucleotides do to the genetic code?

Answer 13

Shifts the translational reading frame (codons)

Question 14

Frameshift mutation def.

Answer 14

occurs when shifting of the codons occurs; affects all amino acids downstream from addition or deletion

Question 15

Transposable elements def.

Answer 15

special DNA segments that can move spontaneously from gene to gene (transposons)

Question 16

Transposition can be either _____________ or _____________

Answer 16

conservative; replicative

Question 17

Conservative transposition

Answer 17

Transposon is completely removed from one area of a chromosome and reinsterted elsewhere (cut+paste)

Question 18

Replicative transposition

Answer 18

A copy of the transposon is inserted elsewhere in the chromosome (copy+paste)

Question 19

T/F
Mutations are essential for understanding genetics

Answer 19

True

Question 20

Induced mutations def.

Answer 20

Mutations that are intentionally produced

Question 21

Induced mutations can be done via (3)

Answer 21

Chemical mutagens
Transposition
Radiation

Question 22

Chemical mutagens (4)

Answer 22

Nitrous acid
Alkylating agents
Base analogs
Intercalating agents

Question 23

Nitrous acid func.

Answer 23

Converts amino group to a keto group
»cytosine to uracil

Question 24

Alkylating agents func.

Answer 24

Alters hydrogen bonding of bases >>nitrosoguanine

Question 25

Base analog def.

Answer 25

Chemicals that are structually similar to the nitrogenous bases but have slightly altered base pairing properties

Question 26

Intercalating agents def

Answer 26

Molecules that insert themselves between adjacent bases >>ethidium bromide

Question 27

What is it called when transposons are inserted into cells to cause mutations?

Answer 27

Induced transposition

Question 28

What are the two types of radiation?

Answer 28

Ultraviolet light X-rays

Question 29

Ultraviolet light mutation func.

Answer 29

causes covalent bonding between adjacent thymine bases

Question 30

Ultraviolet light ultimately forms what?

Answer 30

thymine dimers

Question 31

Thymine dimers func.

Answer 31

distorts DNA

Question 32

X-ray mutation func.

Answer 32

causes breaks in sugar-phosphate backbone of DNA >>breaks in both strands are often lethal

Question 33

Mechanisms of DNA repair (4)

Answer 33

Proofreading Mismatch Repair Nucleotide excision repair Photoreactivation

Question 34

Proofreading

Answer 34

DNA polymerase removes an incorrectly added base and the correct base is added

Question 35

Mismatch repair occurs in _______ organisms

Answer 35

most

Question 36

Mismatch repair in gram negative bacteria does what?

Answer 36

Parent strand is methylated during DNA replication; the unmethylated daughter strand is scanned by mut proteins

Question 37

Mut protein scanning process

Answer 37

Bind to incorrectly paired daughter strand sections recruit exonuclease to cut out mutated section DNA polymerase rebuilds removed section

Question 38

Nucleotide excision repair actions

Answer 38

Exonuclease removes thymine dimer; DNA polymerase able to rebuild

Question 39

Photoreactivation

Answer 39

Photolyase is activated by sunlight Binds to thymine dimers

Question 40

photolyase binding to thymine dimers does what

Answer 40

breaks down dimer; allowing thymines to reform H-bonds with adenines

Question 41

Gene transfer mechanisms (3)

Answer 41

DNA-mediated transformation Transduction Conjugation

Question 42

Two events that occur in gene exchange

Answer 42

1) Donor DNA is transferred and accepted by recipient cell (Donor DNA is either transformed/Transducted/Conjugated) 2) Donor DNA is integrated into the recipient cell's chromosomes

Question 43

Transformation func.

Answer 43

involves the transfer of naked DNA from the environment to the recipient cell--> naked DNA is integrated into recipient chromosome

Question 44

Naked DNA that is integrated into a chromosome does what

Answer 44

Replaces the homologous gene on the chromosome of the recipient cell

Question 45

Natural transformation occurs when bacterial cells are

Answer 45

competent

Question 46

Competence def. (bio)

Answer 46

A condition where bacterial cells are capable of taking up and integrating larger fragments of DNA

Question 47

When does competence occur in the cell growth phase?

Answer 47

Late log, early stationary phase

Question 48

Artifical competence

Answer 48

ability to render cells artifically competent through electroporation

Question 49

Transduction def.

Answer 49

Bacterial DNA that is transferred from donor to recipient via a bacterial virus

Question 50

Transduction process

Answer 50

Phage infects a new bacterial cell and inserts DNA into cell DNA is integrated and mis-matched pairs are repaired

Question 51

Two types of transduction are

Answer 51

Generalized >>any gene of donor can be transferred Specialized >>only specific genes can be transferred

Question 52

Specialized transduction

Answer 52

During excision phase of viral lysogenic cycle, part of the host cell DNA is incorporated into virus

Question 53

Conjugation

Answer 53

mediated by F plasmid

Question 54

F factor

Answer 54

Plasmid that codes for fertility amongst cells (F factor)