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Genetics > Chapter 18. This is stupid. I am tired. Help me. > Flashcards

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

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Biology 101 flashcards
1
Q

Somatic mutations

A

Arise in somatic tissues, no gametes

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2
Q

Germ-line mutations

A

Produce gametes

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3
Q

Base Substitution

A

1 letter swap

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4
Q

Transition

A

more frequency, purine to purine, pyrimidine to pyrimidine

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5
Q

Transversion

A

Purine to pyrimidine and vis versa

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6
Q

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

A

In-frame insertion/deletion

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7
Q

Expanding nucleotide repeats

A

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

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8
Q

Forward mutation

A

Wild type –> Mutant phenotype

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9
Q

Reverse mutation

A

mutant phenotype –> wild type

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10
Q

Missense mutation

A

change to a different amino acid

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11
Q

Nonsense mutation

A

Sense codon goes to nonsense (stop codon)

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12
Q

Silent mutation

A

Codon changes, but same amino acid

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13
Q

Neutral mutation

A

amino acid changes, but no change in gene function

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14
Q

Loss of function mutation

A

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

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15
Q

Gain of function mutation

A

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

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16
Q

Conditional mutation

A

expressed only under certain conditions (ex: temperature)

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17
Q

Lethal mutation

A

Cause premature death

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18
Q

Suppressor mutations

A

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

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19
Q

Intragenic suppressor mutations

A

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

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

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20
Q

Intergenic Suppressor mutations

A

Occurs at gene other than the one bearing the original mutation

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

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21
Q

Mutation Rates depend on what 3 factors?

A
  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
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22
Q

Spontaneous replication errors: Tautomeric shifts

A

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

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23
Q

Spontaneous replication errors: Mispairing due to wobble

A

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

24
Q

Spontaneous replication errors: Incorporation errors and replication errors

A

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

25
Q

Spontaneous replication error: strand slippage

A

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

26
Q

Spontaneous unequal crossing over

A

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.

27
Q

Spontaneous CHEMICAL changes: Depurination

A

loss of purine group
Covalent bond breaks

What goes in apurine site? Usually A.

28
Q

Spontaneous CHEMICAL changes: deamination

A

Loss of NH2 from base

Cytosine –> Uracil
5mC –> Thymine

29
Q

Chemically Induced Mutations: Base analogs

A

Chemicals with structures similar to any of the four standard bases of DNA

5Bromouracil similar to thymine
2aminopurine is analog to adenine

30
Q

Chemically Induced Mutations: Alkylating Agents

A

Donate alkyl group- methyl or ethyl

Ex: EMS- reversible
CG –> TA (+ethyl to G)
TA –> CG (+ethyl to T)

Ex: Mustard Gas

31
Q

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

A

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
32
Q

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

A

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

33
Q

Chemically Induced Mutations: Oxidative Radicals, ex: hydrogen peroxide

A

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

34
Q

Chemically Induced Mutations: Intercalcting Agents

A

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

35
Q

Radiation: UV light

A

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

36
Q

Transposable Element characteristics

A

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)

37
Q

Replicative transposable element

A

Copy & paste

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

38
Q

Non-replicative transposable element

A

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.

39
Q

Transposable example: Grapes

A

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

40
Q

3 common steps of the transposones

A
  1. Staggered breaks in target DNA
  2. Transposable element joined to single stranded ends of target DNA
  3. DNA replicated at single stranded gaps
41
Q

Transposable enzyme

A

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

42
Q

DNA transposons

A

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

43
Q

Retrotransposons

A

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

44
Q

Bacteria Transposable elements: Insertion sequence

A

carries only genetic information necessary for its movement

45
Q

Bacteria transposable elements: Composite transposons

A

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

46
Q

Bacteria transposable elements: Noncomposite transposons

A

Lack insertion sequences

47
Q

Bacteria Transposable elements: transposing bacteriophages

A

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

48
Q

Corn: Transposones

A

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.

49
Q

DNA repair; Mismatch Repair

A

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

50
Q

DNA repair: Direct repair

A

Restores original structures.

Ex: Alkylation/covalent bonds in T dimers with photolyase

51
Q

DNA repair: Base excision repair

A

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

52
Q

DNA repair: Nucleotide-Excision Repair

A

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
53
Q

Homologous recombination

A

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

54
Q

Nonohomologous recombination

A

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

55
Q

What type of DNA repair system:

DNA glycosylases cleave stuff

A

Base excision

56
Q

What type of DNA repair:

Relies on enzymes that have more than 1 protein molecules

A

Nucleotide excision

57
Q

Which is more common: spontaneous or induced?

A

Induced

Genetics (15 decks)

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