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genetics > lecture 29 > Flashcards

lecture 29 Flashcards

mutations pt.2

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1
Q

what is a base analog(antimetabolite) of uracil that can replace thymine in a strand of DNA?

A

5-bromouracil

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2
Q

what are very unstable and quick reacting molecules that “steal” electrons from nearby stable molecules?

A

free radicals

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3
Q

what type of environmental factor causes pyrimidine dimers by the formation of covalent linkages localized on cysteine double bonds?

A

UV light

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4
Q

what does ectopic recombination cause?

A

chromosome duplication

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5
Q

in terms of evolution, what role do transposons have?

A

they increase the genome size as they generate some type of mutation when they move

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6
Q

what class of TEs require reverse transcriptase in order to move?

A

class 1

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7
Q

what class of TEs do NOT require reverse transcriptase in order to move?

A

class 2

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8
Q

what protein do all DNA transposons(class 2) code for?

A

transposase

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9
Q

what class of transposons moves through the genome in a “cut and paste” mechanism?

A

class 2 - DNA transposons

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10
Q

what does TIR stand for?

A

terminal inverted repeats

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11
Q

what recognizes the TIRs at the ends of the TE?

A

transposase

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12
Q

what does (F)DR stand for?

A

(flanking) direct repeats

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13
Q

are (F)DR a part of the TE?

A

no

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14
Q

what provides a marker for the excision site of the TE once it has been removed?

A

(F)DRs

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15
Q

what allows retrotransposons to function?

A

RNA intermediates

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16
Q

do retrotransposons code for transposase?

A

no

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17
Q

what class of TEs move throughout the genome in a “copy and paste” mechanism?

A

class 1 - retrotransposons

18
Q

what do retrotransposons produce?

A

RNA transcripts

19
Q

what must happen in order for a retro-transposon to bind?

A

reverse transcriptase must reverse transcribe the RNA into DNA sequence PRIOR to insertion into target DNA

20
Q

what are LTRs?

A

long terminal repeats; located on each end of TE

21
Q

what are the only active class of transposons in humans?

A

non-long terminal repeats

22
Q

what must non-autonomous transposons borrow to move?

A

reverse transcriptase

23
Q

what are LINEs?

A

long interspersed elements, a type of autonomous retrotransposon

24
Q

what proteins do FUNCTIONAL L1 elements encode?

A

endonuclease and reverse transcriptase

25
Q

what does endonuclease do?

A

cuts DNA

26
Q

what does reverse transcriptase do?

A

makes a DNA copy of an RNA transcript

27
Q

what do NON-functional L1 elements do?

A

play a role in regulating the efficiency of transcription of the gene in which they reside

28
Q

what are SINEs?

A

short interspersed elements, a type of non-autonomous retrotransposon

29
Q

what are short DNA sequences that represent reverse transcribed RNA molecules originally transcribed by RNA polymerase II?

A

SINEs

30
Q

what are the most abundant SINEs?

A

Alu elements

31
Q

Alu elements consist of a sequence that contains a site that is recognized by Alu1 which is what?

A

restriction enzyme

32
Q

where do Alu elements normally occur?

A

introns

33
Q

how does an Alu element end up being translated into the protein product if it begins in an intron?

A

it can be spliced into mRNA, thereby creating a new exon which is translated

34
Q

what does alternative splicing allow for in terms of Alu elements?

A

nature can try out new proteins without losing the original, functioning one

35
Q

what is the main factor for transposable element function?

A

where it lands

36
Q

if a transposable elements lands in a non-coding region, what effect does it have?

A

not much

37
Q

if a transposable element lands in a gene, what effect does it have?

A

mutation, leading to genetic diversity

38
Q

assume the V gene regulates anthocyanin pigment production in black grapes. when a G retrotransposon is added to the V gene, what is the phenotypic result?

A

white grapes

39
Q

what effect does the G retrotransposon have on the V gene in grapes?

A

it disrupts anythocyanin synthesis, thereby preventing color from being made, resulting in white grapes

40
Q

assume a white grape undergoes a second mutation wherein the G retrotransposon is removed; however a piece is left behind. what is the phenotypic result and why?

A

red grapes, because anthocyanin production is partially restored

genetics (30 decks)

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