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Flashcards in Gene expression Deck (53):
1

Selective gene expression allows cells to

efficient, synthesizing only what is needed for each cell type

2

Multicellular eukaryotes consists of and is distinguished based on

a mixture of specialized or differentiated cell types

based on difference in appearance and protein products

3

Cell differentiation

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

4

What are the five levels of gene expression

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

5

What does Gene amplification
do?

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

6

mammalian RBCs discard nuclei after enough hemoglobin mRNA is made

Gene deletion

7

DNA rearrangement is when

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

8

DNA Methylation is associated with

Inactive Regions of the Genome

9

Addition of methyl groups to selected cytosine bases does what

silencing of gene expression

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

10

Methylation patterns are ___ and can cause

inherited
causes epigenetic changes

11

some degree of chromatin decondensation (unfolding) is necessary for

the expression of eukaryotic genes
- to give transcription factors and RNA polymerase access to DNA

12

DNA is packaged by ____ that bid to the DNA

Histone proteins

13

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

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

14

a group of non-histone proteins associated with isolated chromatin

HMG

15

What has large contents of HMG

Transcriptionally active chromatin

16

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

given type of RNA polymerase

17

General transcription factors assemble with RNA polymerase II at

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

18

Regulatory transcription factors

increase (or decrease) transcription initiation

19

Proximal Control Elements are located

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

20

What is the difference between activators and repressors

Enhancers stimulate gene expression
Silencers inhibit gene expression

21

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

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

22

Modify chromatin/nucleosome structure

Coactivator proteins
– SWI/SNF family of coactivators

23

What allow non-adjacent genes to be regulated in a coordinated fashion
-turn transcription on or off
-environmental or developmental signals

DNA response elements

24

What is post transcriptional regulation

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

post transcriptional regulation can control by:

-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

What does RNA processing do?

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

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

Nuclear export

28

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

trigger by a stimulus signal

29

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

nuclear export signal

30

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

translational control mechanisms

31

Translational control mechanisms work by

- altering ribosomes or protein synthesis factors or
- regulating the activity or stability of mRNA

32

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

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

33

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

stimulated in the presence of iron.

34

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

Regulation of mRNA degradation

35

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

controlling mRNA stability

36

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

less stable

37

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

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

38

RNA interference utilizes small RNAs to

to silence the expression of genes

39

RNA interference by dsRNA:

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

Dicer

40

RNA interference by dsRNA:

siRNA binds RISC proteins and one strand is

degraded

41

siRISC (remaining strand + RISC) binds to mRNA via

complementary base pairing

42

MicroRNAs (miRNAs) are a class of

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

43

miRNAs bind to and regulate

regulate the expression of mRNAs
Genes coding for miRNAs accounts for up to 5% of eukaryotic genes

44

What plays an important role in embryonic development

Translational silencing by microRNAs

45

What are Posttranslational modifications of protein structure, function

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

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

rate of degradation and rate of production

47

The half-lives of cellular proteins range from a

few minutes to several weeks

48

dependent protein degradation

Ubiquitin

49

What is Ubiquitin

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

50

What are the three components of Ubiquitin

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

51

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

E1

52

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

Lys

53

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

‘Proteasomes’