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AP Biology Semester 1 > Chapter 18 > Flashcards

Chapter 18 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

how can a cell regulate the production of enzymes?

A

by feedback inhibition or by gene regulation

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2
Q

operons

A

the entire stretch of DNA that includes the operator, the promoter, and the genes they control

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3
Q

operator

A

the regulatory “switch” is a segment of DNA called an operator
-positioned within the promoter

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4
Q

repressor

A

a protein that switches off the operon

-the repressor prevents gene transcription by binding to the operator and blocking RNA polymerase

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5
Q

regulatory gene

A

the repressor is the product of a separate regulatory gene

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6
Q

corepressor

A

a molecule that cooperates with a repressor protein to switch an operon off

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7
Q

how can a repressor be in an active or inactive form?

A

depends on the presence of other molecules

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8
Q

by default the trp operon is __ and the genes for tryptophan synthesis are (not transcribed/transcribed)

A
  • on

- transcribed

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9
Q

what happens when tryptophan is present?

A

binds to the trp repressor protein and turns the operon off

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10
Q

when tryptophan levels are high what does this mean?

A

operon is turned off if tryptophan levels are high

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11
Q

what is a repressable operon?

A

one that is usually on, binding of a repressor to the operator shuts off transcription

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12
Q

trp operon is a ____ _____

A

repressible operon

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13
Q

inducible operon

A

one that is usually off; a molecule called an inducer actives the repressor and turns on transcription

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14
Q

lac operon is an ____ operon and contains genes that code for enzymes used in the hydrolysis and metabolism of lactose

A

inducible

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15
Q

when the lac repressor is active what does this do to the lac operon

A

when the lac repressor is active, it switches the lac operon off

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16
Q

inducer

A

inactivates the repressor to turn the lac operon on

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17
Q

CAP (catabolite activator protein)

A

postive control through a stimulatory protein

  • when CAP is activated it attaches itself to the promoter of the lac operon and increases the affinity of RNA polymerase, thus accelerating transcription
  • when glucose levels increase CAP detaches its self from the lac operon and transcription returns to normal rate
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18
Q

in multicellular organisms, regulation of gene expression is ______

A

-essential for cell specialization

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19
Q

differential gene expression

A

the expression of different genes by cells with the same genome
-abnormalities can lead to diseases like cancer

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20
Q

what can be done to influence both chromatin structure and gene expression

A

chemical modifications to histones and DNA of chromatin

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21
Q

histone acetylation

A

acetyl groups are attached to positively charged lysines in histone tails
-this loosens chromatin structure and thus promoting the initiation of transcription

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22
Q

methylation

A
  • addition of methyl groups

- this condenses chromatin

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23
Q

phosphorylation

A

-addition of phosphate groups next to methylated amino acid to loosen chromatin as well

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24
Q

histone code hypothesis

A

proposes that specific combinations of modifications, as well as the order in which they occur, help determine chromatin configuration and influence transcription

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25
Q

DNA methylation

A

the addition of methyl groups to certain bases in DNA

  • associated with reduced transcription in some species
  • can cause long term inactivation of genes in cellular differentiation
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26
Q

genomic imprinting

A

methylation regulates expression of either the maternal or paternal alleles of certain genes at the start of development

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27
Q

epigenetic inheritance

A

The inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence
-so smoking before the age of 12 can cause your children to be obese (example)

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28
Q

how do chromatin-modfying enzymes provide initial control of gene expression?

A

by making a region of DNA either more or less able to bind the transcription machinery

29
Q

control elements

A

segments of noncoding DNA that serve as binding sites for transcription factors that help regulate transcription

30
Q

transcription factors

A
  • essential for the transcription of all protein-coding genes
  • to initiate transcription; gives assistance
  • high levels of transcription of particular genes depend on control elements interacting with specific transcription factors
31
Q

enhancers

A

distal (situated away from the body) control elements

32
Q

proximal control elements

A

-located close to the promoter

33
Q

activator

A

a protein that binds to an enhancer and stimulates transcription of a gene

  • have two domains
    (1) binds to DNA
    (2) activates transcription
34
Q

what do bound activators facilitate?

A

a sequence of protein-protein interactions that result in transcription of a given gene

35
Q

true or false:

some transcription factors can function as repressors, inhibiting expression a gene

A

true

36
Q

does each eukaryotic gene have its own promoter and control elements?

A

yes, a prokaryotic operon doesn’t

37
Q

alternative RNA splicing

A

different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns

38
Q

which is more long lived in the cytoplasm? eukaryotic mRNA or porkaryotic mRNA

A

eukaryotic mRNA

39
Q

the nucleotide sequences that influence the lifespan of mRNA in eukaryotes reside in….

A

the untranslated region (UTR) at the 3’ end of the molecule

40
Q

what do the regulatory proteins that bind to sequences or structures of the mRNA do?

A

block the initiation of translation of selected mRNAs

41
Q

proteasomes

A

giant protein complexes that bind to protein molecules and degrade them

42
Q

where does noncoding RNAs regulate gene expression (2)

A
  1. mRNA translation

2. chromatin confiugaration

43
Q

true or false:

A significant amount of the genome may be transcribed into noncoding RNAs (ncRNAs

A

true

44
Q

MicroRNAs

A

small single stranded RNA molecules that can bind to mRNA

-these can degrade mRNA or block its translation

45
Q

RNA interference

A

inhibition of gene expression by RNA molecules

46
Q

what causes RNA interference?

A

small interfering RNAs

  • similar to microRNAs
  • induce heterochromatin (making DNA tighter) thus can block large regions of the chromosome (in some yeasts)
47
Q

cell differentiation

A

the process by which cells become specialized in structure and function

48
Q

morphogenesis

A

the physical processes that give an organism its shape

49
Q

cytoplasmic determinants

A

maternal substances in the egg that influence early development

50
Q

induction

A

signal molecules from embryonic cells cause transcriptional changes in nearby target cells
-thus, interactions between cells induce differentiation of specialized cell types

51
Q

determination

A

commits a cell to its final fate

  • determination precedes differentiation
  • cell differentiation is marked by the production of tissue-specific proteins
52
Q

myoblasts

A

produce muscle specific proteins and form skeletal muscle cells

53
Q

MyoD

A

one of several “master regulatory genes” that produce proteins that commit the cell to becoming a skeletal muscle
-a transcription factor that binds to enhancers of various target genes

54
Q

pattern formation

A

the development of a spatial organization of tissues and organs
-pattern formation begins with the establishment of the major axes

55
Q

positional information

A

the molecular cues that control pattern formation, tells a cell its location relative to the body axes and to neighboring cells

56
Q

homeotic genes

A

control pattern formation in late embryo, larva, and adult stages

57
Q

maternal effect genes

A

cytoplasmic determinants that initially establish the axes of the body of Drosophila

58
Q

egg polarity genes

A

maternal effect genes can also be called this…control orientation of the egg and the consequently of the fly

59
Q

bicoid

A

maternal effect gene

–affects the front half of the body

60
Q

morphogens

A

establish an embryo’s axes and other features

61
Q

what are the three reasons bicoid research is important?

A
  1. identified a specific protein required for some early steps in pattern formation
  2. increased understanding of the mother’s role in embryo development
  3. demonstrated a key developmental principle that a gradient of a molecule can determine polarity and position in the embryo
62
Q

oncogenes

A

cancer causing genes

63
Q

proto-oncogenes

A

corresponding normal cellular genes that are responsible for normal cell growth and division

64
Q

how can oncogenes be converted to oncogenes

A
  1. movement of DNA within the genome; if it ends up near an active promoter, transcription may increase
  2. amplification of a proto-oncogene; increases the number of copies of the genes
  3. point mutations in the proto-oncogene or its control elements; cause an increase in gene expression
65
Q

tumor suppressor genes

A

help prevent uncontrolled cell growth

-mutations that decrease protein products of tumor suppressor genes may contribute to cancer onset

66
Q

what are three things tumor suppressor genes can do?

A
  1. repair damaged DNA
  2. control cell adhesion
  3. inhibit cell cylce in the cell cignaling pathway
67
Q

what is common in human cancers?

A

*mutations in the ras proto-oncogene and p53 tumor suppressor gene

68
Q

what happens if there is a mutation in the ras gene

A

can lead to production of a hyperactive Ras protein and increased cell division

AP Biology Semester 1 (21 decks)

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