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Genetics > Gene Regulation > Flashcards

Gene Regulation Flashcards

1
Q

purpose of aminoacyl tRNA synthetase (ARS)

A

“recharge” “empty” tRNAs with the correct amino acid

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2
Q

how many ARS’s do we have?

A

one ARS for each amino acid; specific for one amino acid

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3
Q

enzymatic basis of the genetic code

A

aminoacyl tRNA synthetases

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4
Q

the redundancy in the genetic code arises because

A

some amino acids are coded for by multiple codons

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5
Q

where does transcription and translation happen in eukaryotes?

A

transcription happens in the nucleus; translation happens in the cytoplasm

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6
Q

where does transcription happen in prokaryotes?

A

prokaryotes have no nucleus, so transcription and translation can happen simultaneously in the cytoplasm

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7
Q

do prokaryotes do RNA processing?

A

prokaryotes don’t have introns and don’t process RNA transcripts (no splicing, caps, or tails)

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8
Q

why are genes differentially regulated?

A

every cell in our body has the same genome; however the body consists of trillions of cells and millions of distinct cell types

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9
Q

define differential gene expression (gene regulation)

A

results in different cell types expressing (transcribing and translating) different proteins

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10
Q

what is a cell’s structure and function defined by?

A

which genes it turns on and which genes it turns off

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11
Q

ARS genes are an example of what kind of genes

A

housekeeping genes

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12
Q

what allows cells and organisms to respond to their environment?

A

gene regulation

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13
Q

mechanism of insulin

A

high BG —> pancreatic B cells detect high BG —> B cells transcribe and translate more insulin —> insulin tells fat cells to take in glucose —> lower BG

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14
Q

how are alpha cells different from beta cells?

A

alpha cells always make glucagon and store it up until it is needed

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15
Q

where can gene expression be regulated?

A

transcription, pre-mRNA processing, mRNA degradation, translation, post-translational modifications to proteins, protein degradation

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16
Q

what is the main process controlling if a gene is turned on/off and at what level (how much protein is expressed)?

A

transcriptional regulation

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17
Q

where is the promoter located?

A

right next to the first exon

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18
Q

what are enhancers and where are they located?

A

transcription factors must bind enhancers in order to bind the promoter, but enhancers can be located far from the gene (before, after, or in the introns)

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19
Q

what are CIS-Regulatory Elements (CREs)?

A

DNA sequences on the same (cis) piece of DNA as a gene that regulate transcription of the gene

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20
Q

examples of CREs

A

enhancers and promoters

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21
Q

what must happen for transcription factors to bind enhancers and promoters at the same time?

A

the DNA between the enhancers and promoters bends

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22
Q

steps of transcription factors binding DNA

A

1) TFs bind enhancers
2) DNA bends via bending proteins so TFs can bind promoter
3) “pre-initiation complex” = enhancer + T.F. + promoter + RNA polymerase

23
Q

describe the structure of enhancers

A

consist of many short DNA sequences (4-12 nucleotides) called transcription factor binding sites (TBSs) - transcription factors like particular sequences

24
Q

how many TBSs does a transcription factor have?

A

several potential TBSs

25
Q

where does the TF bind the enhancer?

A

several different places

26
Q

how many transcription factors bind a certain enhancer? why is this important?

A

several kinds of TFs bind the enhancer, this is important because many TF molecules need to bind to each other to stabilize their binding to the enhancer (TFs + enhancer complex must be stable to bind to the promoter and activate transcription)

27
Q

what is the threshold for enhancers?

A

they do not act in an all or nothing manner, as long as a minimum threshold of TFs bind stably, transcription will happen at some level (40, 75 or 100% max transcription)

28
Q

do all your cells have the same enhancers and promoters?

A

yes, same genome so same enhancers and promoters

29
Q

why are cells ultimately different from one another?

A

they have different transcription factors

30
Q

what do specific levels of transcription depend on?

A

cell type and environment

31
Q

how long does the “binding” between enhancers, TFs, and promoters last?

A

temporary, lasting only seconds or minutes usually

32
Q

why can beta cells express insulin?

A

they have transcription factor PDX-1

33
Q

how do the transcription factors present in different cells compare?

A

cells have some of the same TFs, but don’t ever have the exact same combo, cells are defined by the combo of TFs they have

34
Q

how many TFs are there?

A

~2000

35
Q

how can genes that aren’t being used be shut off semi-permanently?

A

via changes in chromatin structure

36
Q

what sort of chemical modifications can be made to DNA to “shut them off”?

A

1) methylation of DNA
2) deacetylation of histones that wrap of DNA can cause regions of the genome to be blocked from transcription

37
Q

how is RNA processing involved in gene regulation?

A

different exons of the same gene can be combined into different mRNAs and create different protein isoforms from the same gene (alternative splicing)

38
Q

define splice factors

A

RNA-binding proteins expressed in different cell types that bind to pre-mRNA and direct the spliceosome to remove different exons and introns

39
Q

how is mRNA transcript degradation regulated?

A

by tiny micro RNAs (miRNAs) transcribed from mi RNA genes

40
Q

role of miRISCs

A

(miRNA + proteins) bind the 3’ UTRs and direct mRNA degradation

41
Q

how many enhancers does one gene have?

A

may have several enhancers

42
Q

where can enhancers be located?

A

5’ (upstream) or 3’ (downstream) of the promoter, or even in introns, not usually in protein coding exons

43
Q

why do genes have multiple enhancers?

A

each enhancer typically controls transcription of the gene in a specific cell or tissue type, or at a specific time (i.e. each enhancer has different TBSs so it can be bound by the TFs present in them various cells and tissues (and times) where it is transcribed

44
Q

what is it called when a gene is used in multiple cell and tissue types

A

pleiotropic gene (i.e. keratin)

45
Q

how many protein coding genes are in the human genome?

A

20,000 protein-coding genes

46
Q

how many cells are we made of?

A

30,000,000,000,000 (30 trillion)

47
Q

how many of your protein coding genes are pleiotropic?

A

most if not all

48
Q

what are most phenotypic differences within species and between species due to?

A

enhancer mutations

49
Q

which proteins regulate splice factors expressed in which cell types?

A

transcription factors

50
Q

miRISC

A

miRNA induced silencing complex

51
Q

how might miRNAs inhibit translation?

A

by blocking ribosome binding (initiation) or elongation, usually by binding the 3’ UTR

52
Q

how can protein activity be regulated?

A

post-translational modifications such as phosphorylation or methylation can turn proteins on or off

53
Q

role of proteasomes

A

degrade proteins that are tagged for destruction with ubiquitins

Genetics (11 decks)

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