Chapter 18. This is stupid. I am tired. Help me.

Question 1

Somatic mutations

Answer 1

Arise in somatic tissues, no gametes

Question 2

Germ-line mutations

Answer 2

Produce gametes

Question 3

Base Substitution

Answer 3

1 letter swap

Question 4

Transition

Answer 4

more frequency, purine to purine, pyrimidine to pyrimidine

Question 5

Transversion

Answer 5

Purine to pyrimidine and vis versa

Question 6

What type of insertion/deletion does NOT affect reading frame?

Answer 6

In-frame insertion/deletion

Question 7

Expanding nucleotide repeats

Answer 7

increase number of copies of a set of nucleotides
Fragile X sites
Formation of hairpins/other secondary structures

Question 8

Forward mutation

Answer 8

Wild type –> Mutant phenotype

Question 9

Reverse mutation

Answer 9

mutant phenotype –> wild type

Question 10

Missense mutation

Answer 10

change to a different amino acid

Question 11

Nonsense mutation

Answer 11

Sense codon goes to nonsense (stop codon)

Question 12

Silent mutation

Answer 12

Codon changes, but same amino acid

Question 13

Neutral mutation

Answer 13

amino acid changes, but no change in gene function

Question 14

Loss of function mutation

Answer 14

complete OR PARTIAL absence of normal protein function, alters structure so can’t work correctly

Question 15

Gain of function mutation

Answer 15

cell now produces protein/gene whose function is not normally present.

Question 16

Conditional mutation

Answer 16

expressed only under certain conditions (ex: temperature)

Question 17

Lethal mutation

Answer 17

Cause premature death

Question 18

Suppressor mutations

Answer 18

mutations that hides the effect of another mutation. NOT REVERSE MUTATION: occurs at site distinct from site of original mutation. Ex: Flies eyes. A-B+ will be white eyes, but A- B- makes them red again

Question 19

Intragenic suppressor mutations

Answer 19

takes place in the same gene as that containing the mutation being suppressed.

Ex: AAT –> AAA –> GAA
Leu – > Phe –> Leu

Question 20

Intergenic Suppressor mutations

Answer 20

Occurs at gene other than the one bearing the original mutation

Ex: AUC can pair with stop codon UAG, so it keeps going

Question 21

Mutation Rates depend on what 3 factors?

Answer 21

1. Frequency with which changes in DNA take place
2. Probability that when alteration in DNA takes place, it will be repaired
3. Probability that mutation will be detected

Question 22

Spontaneous replication errors: Tautomeric shifts

Answer 22

Not a lot of evidence, position of protons in DNA bases change allowing non- Watson and Crick base pairing

Question 23

Spontaneous replication errors: Mispairing due to wobble

Answer 23

Due to flexibility in DNA helical structure. Responsible for mispairings.
T-G wobbles
C-A wobble

Question 24

Spontaneous replication errors: Incorporation errors and replication errors

Answer 24

Replication error, mispaired base is incorporated into newly synthesized nucleotide chain
Ex:
TTCG, then matches with AGGC, then at next round of replication, G pairs with C, leading to transition mutations

Question 25

Spontaneous replication error: strand slippage

Answer 25

One nucleotide strand forms a small loop Due to repeats of one specific base If newly synthesized strand loops, addition of nucleotide If template loops, deletion of one nucleotide

Question 26

Spontaneous unequal crossing over

Answer 26

Misaligned pairing has crossing over resulting in insertion in one and deletion in the other. If homologous chromosomes misalign during crossing over, one crossover product contains an insertion and the other has a deletion.

Question 27

Spontaneous CHEMICAL changes: Depurination

Answer 27

loss of purine group Covalent bond breaks What goes in apurine site? Usually A.

Question 28

Spontaneous CHEMICAL changes: deamination

Answer 28

Loss of NH2 from base Cytosine --> Uracil 5mC --> Thymine

Question 29

Chemically Induced Mutations: Base analogs

Answer 29

Chemicals with structures similar to any of the four standard bases of DNA 5Bromouracil similar to thymine 2aminopurine is analog to adenine

Question 30

Chemically Induced Mutations: Alkylating Agents

Answer 30

Donate alkyl group- methyl or ethyl Ex: EMS- reversible C*G --> T*A (+ethyl to G) T*A --> C*G (+ethyl to T) Ex: Mustard Gas

Question 31

Chemically Induced Mutations: Deaminating Chemicals- Nitrous Acid (HNO2)

Answer 31

Transition mutations- reversible 1. Deaminates (-NH2) cytosine to create uracil 2. Deaminates guanine to create xanthine, which could pair with cytosine (norm) or thymine 3. Changes A to hypoxanthine, which pairs with cytosine

Question 32

Chemically Induced Mutations: Hydroxylamine- adds hydroxyl group (NH2OH)

Answer 32

Nonreversible CG -- >TA only Add hydroxyl group to cytosine, creates hydroxylaminocytosine

Question 33

Chemically Induced Mutations: Oxidative Radicals, ex: hydrogen peroxide

Answer 33

Damage DNA GC --> TA TRANVERSION Guanine to something that mispairs with A

Question 34

Chemically Induced Mutations: Intercalcting Agents

Answer 34

Produce mutations by sandwiching themselves between adjacent bases in DNA, distorting 3D structure of the helix and causing single nucleotide insertions and deletions in replication Frameshift mutations, insertions, deletions Reversible Ex: acridine orange, proflavine, ethidium bromide

Question 35

Radiation: UV light

Answer 35

Pyrimidine dimers (thymine)- bulky lesions that distort DNA confirmation and block replication. Most repaired, but some escape repair

Question 36

Transposable Element characteristics

Answer 36

Contains terminal inverted repeats 9-40 bp long, inverted complements. Required for transposition. (mirror image, like if you flipped it, it would have opposite base) Flanked by direct repeats (look the exact same)

Question 37

Replicative transposable element

Answer 37

Copy & paste new copy is introduced at new site while old copy remains behind original site. Number of copies of transposable element increases

Question 38

Non-replicative transposable element

Answer 38

Cut & Paste Excises transposable element from old site and inserts it at new site without any increase in number of copies. Requires replication of only the few nucleotides that constitute the flanking direct repeats.

Question 39

Transposable example: Grapes

Answer 39

VvmybA1= black grapes Gret 1 retrotransposon - comes in and makes white grapes. Second mutation? removes most of the retrotransposon removed, but a bit remains. So red grapes

Question 40

3 common steps of the transposones

Answer 40

1. Staggered breaks in target DNA 2. Transposable element joined to single stranded ends of target DNA 3. DNA replicated at single stranded gaps

Question 41

Transposable enzyme

Answer 41

Used to make staggered breaks in DNA and to integrate transposable element into new site.

Question 42

DNA transposons

Answer 42

Class 2 Short terminal inverted repeats, short flanking diredt repeats Transposases gene

Question 43

Retrotransposons

Answer 43

Class 1 Long terminal direct repeats, short flanking direct repeats at target site Reverse transcriptase gene

Question 44

Bacteria Transposable elements: Insertion sequence

Answer 44

carries only genetic information necessary for its movement

Question 45

Bacteria transposable elements: Composite transposons

Answer 45

Any segment DNA that becomes flanked by two copies of an insertion sequence may itself transpose Transposase produced by one of the insertion sequences catalyzes the transposition of both, so they move together

Question 46

Bacteria transposable elements: Noncomposite transposons

Answer 46

Lack insertion sequences

Question 47

Bacteria Transposable elements: transposing bacteriophages

Answer 47

a few bacteriophage genomes reproduce by transposition and use transposition to insert themselves in their lysogenic cycle

Question 48

Corn: Transposones

Answer 48

Ds can transpose, only if Ac present CC/Cc= purple, cc= colorless/white DS in C allele? welp, no more pigment (Ct) Ctc & Cc mix? purple spots.

Question 49

DNA repair; Mismatch Repair

Answer 49

Mismatched base added. But wait! old strand methylated, but new strand not! so the mismatched repair complex brings mismatch based close to methylated sequence Exonucleases remove nucleotides

Question 50

DNA repair: Direct repair

Answer 50

Restores original structures. | Ex: Alkylation/covalent bonds in T dimers with photolyase

Question 51

DNA repair: Base excision repair

Answer 51

Modified base excise, entire nucleotide replaced. 1. Excision catalyzed by DNA glycosylases. 2. Base removed, so AP enzyme endonuclease cuts phosphodiester bond 3. DNA polymerase add new nucleotides to exposed 3'-OH 4. Nick selected by DNA ligase Eukaryotes used DNA polymerase beta, which has no proofreading, so AP endonucleases have to do it

Question 52

DNA repair: Nucleotide-Excision Repair

Answer 52

Removes bulky DNA lesions 1. Damage to DNA distorts configuration of molecule 2. Enzyme complex recognizes distortion resulting from damage 3. DNA is separated, single strand binding proteins stabilize the single strands 4. Enzyme cleaves strand on both sides of damage 5. part of damage strand removed 6. Gap filled by DNA polymerase and seal by ligase

Question 53

Homologous recombination

Answer 53

repairs by using identical genetic info in another DNA molecule using same method in homologous crossing over

Question 54

Nonohomologous recombination

Answer 54

repairs without using homologous template. Used when cell is in G1 and sister chromatid not available for repair.

Question 55

What type of DNA repair system: DNA glycosylases cleave stuff

Answer 55

Base excision

Question 56

What type of DNA repair: Relies on enzymes that have more than 1 protein molecules

Answer 56

Nucleotide excision

Question 57

Which is more common: spontaneous or induced?

Answer 57

Induced