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Flashcards in Gene Expression Deck (127)
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1
Q

Where is DNA transcribed into RNA?

A

The nucleus

2
Q

Where is RNA processed?

A

The nucleus

3
Q

Where does mRNA exit through?

A

nucleopores

4
Q

Where are ribosomes assembled on mRNA?

A

The cytosplasm

5
Q

Where does translation take place?

A

The cytosplasm

6
Q

What does the SRP do?

A

Directs polypeptides/ribosomes to the ER

7
Q

In which organelle is the signal sequence cleaved?

A

The ER

8
Q

The new protein is synthesized into the lumen of which organelle?

A

The ER

9
Q

From the Golgi Apparatus the newly synthesized protein is moved to a ____, ____, or the ____.

A

vacuole, peroxisome, or plasma membrane

10
Q

Once fused with the plasma membrane, a protein can be released into the ____.

A

cell wall

11
Q

Number of copies of complete genome

A

Ploidy

12
Q

All plant species have at least 1 whole genome duplication event in their evolutionary history. T or F ?

A

True

13
Q

Contains multiple copies of complete genome from a single species

A

Autoploidy

14
Q

Contains multiple copies of complete genome from 2 or more species

A

Allopolylpoidy

15
Q

Loss of DNA segment from chromosome

A

Direct repeats

16
Q

Inversion of DNA segment in chromosome

A

Indirect repeats

17
Q

aka “jumping genes” DNA segment with ability to insert into a new location within genome

A

Transposons

18
Q

The study of changes in organisms caused by modification of gene expression rather than alteration of genetic code itself

A

Epigenetics

19
Q

How many ways can genome duplication occur?

A

Three

20
Q

Chromosomes fail to segregate properly leading to abnormally diploid gametes that fuse to form an allotetraploid plant

A

Meiosis effect

21
Q

Recombination resulting in a gene being separated from its promoter (inactivation) or a gene being placed next to a new promoter (alters gene expression patter)

A

Intramolecular recombination

22
Q

2 classes of transposons

A

Retrotransposons, and DNA transposons

23
Q

The enzyme which synthesizes a DNA copy of a transposon from RNA

A

Reverse transcriptase

24
Q

The enzyme that excises and inserts transposon from DNA into a new place in the genome

A

Transposase

25
Q

What happens when a transposon is inserted into the coding region of a gene?

A

Gene inactivation, protein aborted or functions poorly

26
Q

What happens when a transposon is inserted near the coding region of a gene?

A

Gene inactivation by disrupting promoter-gene relationship, altered gene expression due to promoters on transposon

27
Q

Which type of chromatin makes up 10% of genomic DNA, is in a closed state, with methylated and tightly packed histones, and is transcriptionally inactive?

A

Heterochromatin

28
Q

Which type of chromatin makes up 90% of genomic DNA?

A

Euchromatin

29
Q

Which type of euchromatin is transcriptionally inactive?

A

Euchromatin in intermediate state

30
Q

Which type of euchromatin is transciptionally active?

A

Euchromatin in open state

31
Q

Histone modification associated with gene activation

A

Acetylation

32
Q

Histone modification associated with gene inactivation

A

Methylation

33
Q

Enzymes that remove acetate from H3 and H4 lysines

A

Histone deacetylase

34
Q

Enzymes that transfer acetate from acetyl-CoA to H3 and H4 lysines

A

Histone acetyltransferases (HATs)

35
Q

Enzyme that adds CH3 group to H3 lysines

A

Histone methyltransferases (HMTs)

36
Q

Enzyme that removes CH3 groups from H3 lysines

A

Histone demethylases

37
Q

Enzyme that removes methylated cytosine

A

Glycosylase

38
Q

Enzyme that adds methyl group to cytosine bases at C5 position

A

DNA methyltransferase

39
Q

What is it called when the phenotype of 1 parent is always expressed in progeny of successive generations regardless of genetic contribution of the other parent?

A

Parental imprinting

40
Q

What does the ddm1 mutant refer to?

A

Mutant with a decrease in dna methylation

41
Q

At which end is the initiation site located?

A

5’ end

42
Q

RNA polymerase acts ___ to ___ on template strand.

A

3’, 5’

43
Q

Nascent RNA chain elongates ___ to ___.

A

5’, 3’

44
Q

The region of DNA that is not transcribed into RNA and controls transcription of transcribed region by regulating assembly of transcription initiation complex (TIC) at TATA box

A

Promoter regions

45
Q

A primer is not required to initiate the synthesis of RNA. T or F ?

A

True

46
Q

Where do nuclear RNAPs bind to initiate the synthesis of RNA?

A

To the promoter on the TATA box

47
Q

What is the transcription initiation complex composed of ?

A

RNAPII and 7 TFs

48
Q

What are the 5 TFs common to all 3 RNAPs ?

A

TFIIB, TFIIE, TFIIF, TFIIG, and TFIIH

49
Q

Where is the TATA box located in comparison to the transcription start site (how many bps away, upstream or downstream) ?

A

About 25 bp upstream

50
Q

What is the TFIID complex composed of?

A

1 TBP (TATA-box binding protein) and 8 TAFs (TATA-box additional protein factors)

51
Q

What does TFIIA do?

A

Binds to TFIID complex and releases inhibitor from complex

52
Q

What does TFIIF do?

A

Binds to RNAPII

53
Q

What do TFIIE, TFIIH, and TFIIJ do?

A

Position RNAPII at start site

54
Q

What does TFIIH do?

A

Phosphorylates RNAPII

55
Q

Regulatory elements that control transcription of a gene

A

cis elements

56
Q

Proteins (often dimers) that bind to cis elements

A

Trans-acting factors (aka transcription factors)

57
Q

pgs 53

A

-56 for methods to study cis-trans interactions

58
Q

Key structural features of helix-turn-helix TF motif

A

2 alpha helices separated by a turn, function as dimers

59
Q

Key structural features of helix-loop-helix TF motif

A

Short helix connected to longer helix by loop, function as dimers

60
Q

Key structural features of zinc finger TF motif

A

Various structures coordinated by Zn, function as monomer or dimers

61
Q

Key structural features of leucine zipper TF motif

A

Alpha helix of 35 AA; every 7th AA= Leu, dimerizes along hydrophobic surface

62
Q

Key structural features of basic zipper TF motif (most common among plants)

A

Variation of Leu Zipper with other hydrophobic AAs in place of Leu, dimerizes along hydrophobic surface

63
Q

How many RNAPs do plastids contain ?

A

2; E.coli RNAP and Bacteriophage-like RNAP

64
Q

What subunits is the E.coli type RNAP made of ?

A

4 subunits: 2 alpha, beta prime and beta;

1 regulatory unit: sigma

65
Q

Where are the core subunits encoded?

A

in the plastid genome

66
Q

Where is the regulatory subunit encoded?

A

in the nucleus genome

67
Q

Where is bacteriophage-like RNAP encoded?

A

in the nucleus

68
Q

Clusters of 2 or more genes transcribed by RNAP from single promoter

A

Polycistronic transcription units (PTUs)

69
Q

Plastids adjust number of active promoters depending on stimuli. T or F?

A

True

70
Q

What is the function of the 5’-cap (m7Gppp)?

A

Required for exit from the nucleus, increases efficiency of translation initiation (ribosome loading), and protects against degradation prior to translation

71
Q

Addition of 5’-cap is done by….

A

Addition of guanosine to nascent mRNA, then methylation of guanosine at position N7

72
Q

What is the function of polyadenylation ?

A

Protects against exo-RNase degradation prior to translation, role in initiation of translation

73
Q

Addition of poly-A tail is done by…

A

a signal sequence in 3’-UTR (AAUAAA), downstream sequence cleaved by endonuclease, 20-250 adenosines added to 3–end by poly-A polymerase),

74
Q

What is the function of RNA splicing ?

A

Removal of introns from pre-mRNAs and pre-tRNAs , the release of rRNAs from pre-rRNAs

75
Q

Where are introns located ?

A

In nuclear genes, chloroplast genes, and mitochondria genes

76
Q

How are introns classified?

A

By structural features and splicing mechanism

77
Q

What are the splice sites for pre-mRNA introns?

A

5’ splice site (donor site): 5’-GU

3’ splice site (acceptor site): 3’-AG

78
Q

Where does the branch site structural element bind?

A

To the 5’-end of intron during excision (about 40 nt from 3’ splice site)

79
Q

spliceosome assembly

A

slide 82

80
Q

initiation of splicing

A

slide 83

81
Q

completion of splicing

A

slide 84

82
Q

How do self-splicing introns that form ribozymes work?

A

Guanosine cofactor attacks 5’ splice site, cleavage of 3’ splice site, ligation of exons

83
Q

initiation of self-splicing

A

slide 87-88

84
Q

What functional enzyme do mobile introns contain ?

A

DNA endonuclease

85
Q

What function do DNA nucleases serve in mobile introns?

A

Recognize intron-less allele, generate double-strand break near insertion or “homing” site, initiate replicative integration of intron

86
Q

Which group of self-splicing introns have features in common with nuclear pre-mRNA splicing?

A

Group II

87
Q

What is the difference between Group II self-splicing introns and pre-mRNA splicing?

A

Group II intron does not form spliceosome

88
Q

Where are Group III self-splicng introns found?

A

in Euglenoid plastids

89
Q

Are most mitochondrial mRNAs transcribed as monocistronic units or polycistronic units?

A

Monicistronic

90
Q

5’-end of nuclear mRNA?

A

5’-cap (m7Gppp)

91
Q

5’-end of chloroplast mRNA?

A

5’-monophosphate

92
Q

5’-end of mitochondria mRNA?

A

5’-triphosphate

93
Q

3’-end of nuclear mRNA?

A

Poly-A tail (-AAAA)

94
Q

3’-end of chloroplast mRNA?

A

Stem-loop structure

95
Q

3’-end of mitochondria mRNA?

A

Stem-loop structure

96
Q

What are the precursor sections for nuclear rRNA processing ?

A

17S, 5.8S, and 25S

97
Q

Which precursor sections H-bond after spacer sequence is removed?

A

5.8S and 25S

98
Q

Which section of nuclear rRNA is unusual compared to other rRNAs and why?

A

5S, its transcription is independent of other rRNA genes, requires no processing

99
Q

What is present in most tRNA genes?

A

introns

100
Q

What are tRNAs encoded by ?

A

gene clusters

101
Q

How many tRNAs are present in plastids?

A

30

102
Q

How many tRNAs are present in mitochondria?

A

16

103
Q

Which organelles have/don’t have sufficient tRNA for protein synthesis?

A

Plastids do, Mitochondria don’t

104
Q

What is the minimum requirement for protein synthesis with wobble codons?

A

23 tRNAs

105
Q

What are the 2 RNA editing mechanisms?

A

Insertion/deletion and Conversion (modifications, substitution)

106
Q

Purpose for amino acid conversions?

A

Often to restore highly conserved protein

107
Q

Purpose for ORF conversions?

A

Can shorten open reading frames, may form new start or stop codons

108
Q

Requirements for mRNA translocation ?

A

5’-cap
poly-A tail
introns removed

109
Q

Requirements for rRNA translocation ?

A

PTU cleavage

introns removed

110
Q

Requirements for tRNA translocation ?

A

PTU cleavage

introns removed

111
Q

What are the requirements for gene silencing?

A

dsRNA, Dicer, RISC (RNA induced silencing complex)

112
Q

What does the dicer do?

A

cleaves dsRNA into short or small interfering RNAs (siRNAs)

113
Q

Biological roles for post-transcriptional gene silencing

A

Protection, development , Experimental utility

114
Q

Multiple ribosomes simultaneously translating 1 mRNA

A

Polyribosomes

115
Q

Requirements for protein synthesis

A

mRNA, ribosomes, protein cofactors, enzymes, inorganic ions, GTP, tRNAs, and amino acids

116
Q

A site:

A

aminoacyl-tRNA

117
Q

P site:

A

peptidyl-tRNA

118
Q

E site:

A

uncharged tRNA exiting ribosome

119
Q

What enzyme catalyzes the charging of tRNAs ?

A

tRNA synthetase

120
Q

Components required for initiation?

A

mRNA, charged tRNA(fmet), small ribosomal subunit, large ribosomal subunit, initiation factors (proteins), GTP

121
Q

A ribosomal binding site in mRNA, generally located around 8 bases upstream of start codon AUG. Initiates protein synthesis by aligning the ribosome with the start codon.

A

Shine-Dalgarno sequence

122
Q

What does IF3 do?

A

Binds 30S ribosomal subunit

123
Q

What does IF2 do?

A

Binds GTP, then binds to 30S ribosomal subunit at the P-site

124
Q

What does IF1 do?

A

Binds charged tRNA and deliver tRNA to IF2 bound to 30S subunit

125
Q

What is the enzyme that catalyzes polypeptide elongation?

A

Peptidyltransferase

126
Q

How is the peptide bond formed ?

A

Dehydration, condensation reaction

127
Q

What activity do intervening protein sequences have?

A

endonuclease activity