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Cells and Molecular biology > Gene expression > Flashcards

Gene expression Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Selective gene expression allows cells to

A

efficient, synthesizing only what is needed for each cell type

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2
Q

Multicellular eukaryotes consists of and is distinguished based on

A

a mixture of specialized or differentiated cell types

based on difference in appearance and protein products

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3
Q

Cell differentiation

A

Differentiated cells are produced from groups of immature, non-specialized cells or undifferentiated cells

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4
Q

What are the five levels of gene expression

A
  1. Genome
  2. Transcription
  3. RNA processing and export
  4. Translation, and
  5. Posttranslational events
    Posttranscriptional control
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5
Q

What does Gene amplification

do?

A 
selective replication of specific genes
rRNA genes Xenopus laevis (5.8S, 18S, 28S rRNAs)
500 genes in haploid genome
4000-fold replication during oogenesis
2 million copies in mature oocyte
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6
Q

mammalian RBCs discard nuclei after enough hemoglobin mRNA is made

A

Gene deletion

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7
Q

DNA rearrangement is when

A

Movement of DNA segments from one location to another within the genome

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8
Q

DNA Methylation is associated with

A

Inactive Regions of the Genome

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9
Q

Addition of methyl groups to selected cytosine bases does what

A

silencing of gene expression

-(methylated cytosine tend to cluster near the 5’ ends of the genes – cause methylation of promoters)

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10
Q

Methylation patterns are ___ and can cause

A

inherited

causes epigenetic changes

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11
Q

some degree of chromatin decondensation (unfolding) is necessary for

A

the expression of eukaryotic genes

- to give transcription factors and RNA polymerase access to DNA

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12
Q

DNA is packaged by ____ that bid to the DNA

A

Histone proteins

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13
Q

Tagging of histone molecules by acetyl, methyl and phosphate groups has a ___ which creates ___

A

protruding tail that can be tagged which can create a histone code

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14
Q

a group of non-histone proteins associated with isolated chromatin

A

HMG

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15
Q

What has large contents of HMG

A

Transcriptionally active chromatin

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16
Q

General transcription factors – essential for transcription of all the genes transcribed by a

A

given type of RNA polymerase

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17
Q

General transcription factors assemble with RNA polymerase II at

A

the core promoter, a region immediate to start point and starts transcription at a low level

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18
Q

Regulatory transcription factors

A

increase (or decrease) transcription initiation

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19
Q

Proximal Control Elements are located

A

Located upstream (100-200 bp) & close to core promoter

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20
Q

What is the difference between activators and repressors

A

Enhancers stimulate gene expression

Silencers inhibit gene expression

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21
Q

What are the two principles govern the interaction between enhancers and the genes they regulate

A
  1. Looping - brings enhancer closer to core promoter
    1. Coactivator proteins - mediate the interaction between activators and RNA polymerase complex bound to core promoter
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22
Q

Modify chromatin/nucleosome structure

A

Coactivator proteins

– SWI/SNF family of coactivators

23
Q

What allow non-adjacent genes to be regulated in a coordinated fashion

  • turn transcription on or off
  • environmental or developmental signals
A

DNA response elements

24
Q

What is post transcriptional regulation

A

After transcription, the flow of genetic information involves a complex series of posttranscriptional events, any or all of which can turn out to be regulatory points

25
Q

post transcriptional regulation can control by:

A
  • RNA processing and nuclear export,
  • initiation factors and translational repressors,
  • regulation of mRNA degradation,
  • RNA interference and
  • modifications of protein structure, function and degradation
26
Q

What does RNA processing do?

A

Addition of 5’ cap and a 3’ tail

- Chemical modifications such as methylation
- Alternative splicing – splicing together of exons removing introns, important control as it makes a variety of mRNAs from the same pre-mRNA;
27
Q

After processing, export of mRNA through nuclear pores to the cytoplasm
RNAs with defects in capping or splicing are not readily exported from the nucleus

A

Nuclear export

28
Q

Transport of mRNA through nuclear pores does not take place until their export is

A

trigger by a stimulus signal

29
Q

The amino acid sequence of the Rev protein includes a _____ to guide the viral RNA out through the nuclear pores into the cytoplasm

A

nuclear export signal

30
Q

Once mRNA is in the cytoplasm, these are available to regulate the translation of mRNA to polypeptide

A

translational control mechanisms

31
Q

Translational control mechanisms work by

A
  • altering ribosomes or protein synthesis factors or

- regulating the activity or stability of mRNA

32
Q

Synthesis of globin polypeptide depends on the availability of ‘heme’ which

A

the iron-containing prosthetic group that attaches to globin to form the final product, hemoglobin.

33
Q

Synthesis of ferritin, an iron-storage protein, is selectively

A

stimulated in the presence of iron.

34
Q

The half-life of eukaryotic mRNAs varies widely ranging from 30 minutes or less for some growth factors, and over 10 hours for the mRNA encoding β-globulin

A

Regulation of mRNA degradation

35
Q

The length of poly(A) is one factor that plays a role in

A

controlling mRNA stability

36
Q

are mRNA with short poly(A) tails more or less stable

A

less stable

37
Q

RNA interference or RNAi – based on ability of small RNA to

A

trigger mRNA degradation, or
inhibit mRNA translation, or
inhibit transcription of the gene coding for a particular mRNA

38
Q

RNA interference utilizes small RNAs to

A

to silence the expression of genes

39
Q

RNA interference by dsRNA:

A cytoplasmic nuclease known as ___ cuts dsRNA into 21-22bp fragments (siRNA)

A

Dicer

40
Q

RNA interference by dsRNA:

siRNA binds RISC proteins and one strand is

A

degraded

41
Q

siRISC (remaining strand + RISC) binds to mRNA via

A

complementary base pairing

42
Q

MicroRNAs (miRNAs) are a class of

A

single-stranded RNAs about 21-22 nt in length that are produced by genes found in almost all eukaryotic cells

43
Q

miRNAs bind to and regulate

A

regulate the expression of mRNAs

Genes coding for miRNAs accounts for up to 5% of eukaryotic genes

44
Q

What plays an important role in embryonic development

A

Translational silencing by microRNAs

45
Q

What are Posttranslational modifications of protein structure, function

A

Once polypeptide chain is formed - still many ways of regulating the activity of polypeptide chain
These are posttranslational control mechanisms that are available for modifying protein structure and function

46
Q

Protein degradation are mechanisms that control the amount of any given protein present in a cell is influenced by its

A

rate of degradation and rate of production

47
Q

The half-lives of cellular proteins range from a

A

few minutes to several weeks

48
Q

dependent protein degradation

A

Ubiquitin

49
Q

What is Ubiquitin

A

a small protein chain of 76 amino acids, and is joined to target proteins by a process that involves three components

50
Q

What are the three components of Ubiquitin

A

E1: Ubiquitin-activating enzyme
E2: Ubiquitin-conjugating enzyme
E3: substrate recognition protein

51
Q

Ubiquitin is first activated by attaching it to __ in an ATP-dependent reaction

A

E1

52
Q

Activated ubiquitin is transferred to E2 and subsequently linked to __ residue in the target protein, in a reaction facilitated by E3

A

Lys

53
Q

ubiquitin chains serve as targeting signals that are recognized by protein degrading structures, called

A

‘Proteasomes’

Cells and Molecular biology (6 decks)

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