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mcb181 > Chapter 17 > Flashcards

Chapter 17 Flashcards

1
Q

why are complex traits difficult to see

A

because there are a lot of genes involved

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2
Q

what is epistasis

A

genes interact with one another

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3
Q

what does genotype by environment imply

A

that the interplay between gens and the environment is difficult to predict

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4
Q

where can gene regulation take place

A
  • in the chromosome
  • during transcription
  • during RNA processing
  • RNA stability
  • during translation
  • during post transcriptional modification
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5
Q

what are the different levels gene regulation can occur at

A
  • chemical modification
  • chromosome inactivation
  • trasncriptional regualtion
  • translational regulation
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6
Q

what are the types of chemical modification

A

methylation of cytosine and chromatin remodeling

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7
Q

what happens in methylation

A
  • occurs to cytosine bases that are adjacent to guanosine bases on a DNA strand
  • transcription factors bind to promotor region and recruiters RNA polymerase 2 to start transcription
  • the methylated cytosines inhibit transcription factors from binding to the promotor, so transcription does not occur
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8
Q

what is gene expression

A

genes have been translated

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9
Q

what are epigenetic effects

A

regulation of gene expression caused by mechanisms other retain changes in the DNA sequence

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10
Q

what are examples of epigenetic effects

A

chemical modification of histones and alterations in chromatin structure

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11
Q

what happens in chromatin remodeling

A
  • histone tails are modified through methylation
  • when chromatin is coiled proteins that carry out transcription cannot access the DNA
  • methylation of histone tails allow chromatin to unravel enough for transcriptional enzymes and proteins to access the DNA
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12
Q

how are histone tails modified in chromatin remodeling

A
  • lysine amino acids in the histone tails are methylated

- methyl and acetyl groups can either be added or removed

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13
Q

what is dosage compensation

A

explains the regulation mechanism that differs between males and females in the x-chromosome

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14
Q

what is X-inactivation

A

where only one X chromosome is used in females

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15
Q

what is the mechanism in X-inactivation

A
  1. the Xist gene is transcribed and Xist noncoding RNA binds with the X chromosome inactivation center (XIC)
  2. transcription of Xist continues and the X chromosome becomes coated with Xist RNA
  3. eventually the entire chromosome becomes coated with Xist RNA
  4. presence of Xist RNA triggers DNA methylation and other changes associated with transcription activity
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16
Q

what do small regulatory RNA do

A

regulate gene expression by either binding to transcripts and blocking translation or causing degradation

17
Q

what do micro RNAs do

A
  • they are transcribed just like protein coding genes
  • RNA folds back up on itself to form 1 or more hairpin structures
  • enzymes recognize the folded miRNAs and cleave the stems from the hairpin leaving small double stranded segments
  • one strand of the fragment becomes incorporated into a protein complex called RISC that base pairs with some mismatches with a region of the target mRNA
  • translation is inhibited
18
Q

why do microRNAs buldge

A

imperfect base pairing

19
Q

what do small interfering RNAs do

A
  • they are transcribed and incorporated into the RISC complex like miRNAs
  • when small interfering RNAs pair with a target mRNA there are no mismatches
  • the targeted mRNA is cleaved by RISC which leads to degradation of the RNA transcript
20
Q

why is gene regulation simpler in prokaryotes

A
  1. DNA isn’t packages into chromosomes
  2. mRNA is not processed
  3. there’s no nuclear membrane separating transcription and translation
21
Q

what is positive regulation

A

a regulatory molecule (Activator protein) binds DNA in order for transcription to take place

22
Q

what is the mechanism for positive regulation

A
  1. RNA polymerase can bind to the promotor only if an activator protein binds to site near the promotor
  2. if the activator does not bind to the DNA, the RNA polymerase cannot bind and transcription does not occur
23
Q

what is negative regulation

A

a regulatory molecule (repressor protein) binds DNA in order for transcription to be prevented

24
Q

what is the mechanism for negative regulation

A
  1. when repressor protein is absent, the DNA can recruit the RNA polymerase complex and transcription takes place at a constant rate
  2. when repressor protein is present and can bind to DNA, RNA polymerase cannot bind and there is no transcription
25
Q

what are lacZ and lacY

A

structural genes that code for primary structure of proteins

26
Q

what is the lacI gene and what does it do

A

it encodes the repressor protein and is expressed constantly at a low level

27
Q

what happens in the absence of lactose

A

the repressor protein binds to the operator and prevents transcription from taking place

28
Q

what does lactose do

A

acts as an inducer because it prevents binding of the repressor protein, inducing transcription

29
Q

what is produced when lactose is present

A

allolactose

30
Q

what does allolactose do

A

binds to the repressor and prevents it from binding to the operator

31
Q

what happens if there is a mutation in lacI (repressor)

A

lacY and lacZ are expressed in presence and absence of lactose

32
Q

what happens in cells containing one mutant and one normal copy of lacI

A

lacZ and lacY are expressed only in the presence of lactose

33
Q

what happens if there’s a mutation is lacO (operator)

A

it prevents the repressor protein from binding, so lacZ and lacY are expressed in the presence and the absence of lactose

34
Q

what is CRP-cAMP

A

a positive regulator of the lac operon

35
Q

when more than one energy source is available to the environment what is the order they get used in

A

glucose> lactose> glycerol

36
Q

what happens when glucose is low

A

high cAMP

37
Q

what happens when glucose is high

A

low cAMP

38
Q

what is CRP

A

cAMP receptor protein

39
Q

what is constitutive expression

A

always expressed

mcb181 (20 decks)

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