Gene Expression; from Gene to Protein Flashcards Preview

BIOL-L 112 Exam 3 > Gene Expression; from Gene to Protein > Flashcards

Flashcards in Gene Expression; from Gene to Protein Deck (126):
1

Gene Expression

he process by which DNA directs protein synthesis, includes two stages

2

The two stages of Gene Expression

transcription and translation

3

Central Dogma of Molecular Biology

describes the flow of information from DNA to mRNA to protein.

4

What does the Central Dogma state?

It states that genes specify the sequence of mRNA which specifies the sequence of proteins

5

RNA is the bridge between what?

Genes and the proteins that they code

6

Transcription

The synthesis of RNA using information in DNA, producing mRNA.

7

Translation

The synthesis of a polypeptide, using information in the mRNA, with ribosomes being the sites of translation

8

Prokaryote Transcription and Translation

translation of mRNA can begin before transcription has finished. Transcription & translation are coupled in prokaryotes.

9

Eukaryotic Transcription and Translation

the nuclear envelope separates transcription from translation;Transcription & translation are not coupled.

10

Eukaryotic RNA transcripts are ...

modified through RNA processing to yield the finished mRNA

11

How many amino acids are there?

20

12

How many nucleotide bases in DNA are there?

4

13

What is a Triplet Codon

A series of non-overlapping, three-nucleotide words. The words of a gene are transcribed into complementary non-overlapping three-nucleotide words of mRNA

14

After genes are transcribed into mRNA, what happens next?

These words are then translated into a chain of amino acids, forming a polypeptide

15

What is a Template Strand?

During transcription, one of the two DNA strands, provides a template for ordering the sequence of complementary nucleotides in an RNA transcript.

16

Is the template strand always the same strand for a given gene?

Yes

17

What is the process called from DNA to Pre-mRNA?

Transcription

18

What is the process called from Pre-mRNA to mRNA?

RNA Processing

19

What is the Process called from mRNA to Ribosome?

Translation

20

What comes out of a Ribosome?

Polypeptide

21

In a Bacterial Cell; What happens from DNA to mRNA?

Transcription

22

In a Bacterial Cell; what happens from mRNA to Ribosome?

Translation

23

What are codons?

mRNA base triplets

24

During translation, the mRNA base triplets are read in what direction?

5' --> 3' Direction

25

What is the job of the codon?

To specify the amino acid to be placed at the corresponding position along a polypeptide

26

The genetic code is ___

Redundant ; more than one codon may specify a particular amino acid

27

Of the 64 triplets, how many codes are for amino acids?

61 Codes

28

Of the 64 triplets, how many codes are for "stop" signals to end translation

3 (UAA, UGA, UAG)

29

Of the 64 triplets, how many codes are TO START CODON?

1; AUG

30

Where is non-universal genetic code located?

Found in the Mitochondria and Protists

31

What are the three stages of transcription?

Initiation, Elongation, Termination

32

What is RNA Polymerase

RNA synthesis is catalyzed by this, which pries the DNA strands apart and joins together the RNA nucleotides.

33

What is a Promoter

The DNA sequence that RNA polymerase attaches to

34

What is a transcription unit?

The stretch of DNA that is transcribed

35

Does RNA Polymerase need a Primer??

No

36

How do Promoters start the process?

signal the transcriptional start point and usually extend several dozen nucleotide pairs upstream of the start point

37

What are Transcription Factors?

They mediate the binding of RNA polymerase and the initiation of transcription.

38

What is a Transcription Initiation Complex?

The completed assembly of transcription factors and RNA polymerase II bound to a promoter

39

What is a TATA box?

A promoter, that is crucial in forming the initiation complex in eukaryotes

40

As RNA polymerase move along the DNA, how many does it untwist?

10-20 bases at a time

41

Transcription progresses at a rate of..

40 nucleotides/sec in eukkaryotes

42

Which end are Nuceotides added to?

They are added to the 3' end

43

Termination of Transcription; Bacteria

the polymerase stops transcription at the end of the terminator and the mRNA can be translated without further modification

44

Termination of Transcription; Ekaryotes

RNA polymerase II transcribes the polyadenylation signal sequence; the RNA transcript is released 10–35 nucleotides past this polyadenylation sequence

45

When do enzymes in the eukaryotic nucleus modify pre-mrna?

Before the genetic messages are dispatched to the cytoplasm

46

During RNA processing, what is usually altered?

Both ends of the primary transcript

47

Usually, what sections are cut out and the remaining spliced together?

Introns are cut out, and exons are spliced together

48

Pre-mRNA molecule is modified with the 5' and 3' end recieving what?

The 5' end receives a modified nucleotide 5' cap (Guanine) and the 3' gets a poly-A tail

49

Why do both the 5' and 3' get modified?

They seem to facilitate the export of mRNA to the cytoplasm
They protect mRNA from hydrolytic enzymes
They help ribosomes attach to the 5′ end

50

What are Introns?

They are noncoding regions; where NA transcripts have long noncoding stretches of nucleotides that lie between coding regions

51

What are Exons?

They are eventually expressed, usually translated into amino acid sequences

52

What does RNA cutting & splicing do?

removes introns and joins exons, creating an mRNA molecule with a continuous coding sequence

53

In some cases, what is RNA splicing carried out by?

Spliceosomes

54

What are spliceosomes

consist of a variety of proteins and several small nuclear ribonucleoproteins (snRNPs) that recognize the splice sites.

55

What are Ribozymes?

are catalytic RNA molecules that function as enzymes & can splice RNA.

56

Property of RNA that enables it to function as an enzyme (1)

It can form a three-dimensional structure because of its ability to base-pair with itself

57

Property of RNA that enables it to function as an enzyme (2)

Some bases in RNA contain functional groupsthat may participate in catalysis

58

Property of RNA that enables it to function as an enzyme (3)

RNA may hydrogen-bond with other nucleicacid molecules

59

Importance of Introns?

Some introns contain sequences that may regulate gene expression
Some genes can encode more than one kind of polypeptide, depending on which segments are treated as exons during ,splicing, also known as alternative RNA splicing

60

What are domains?

Proteins often have a modular architecture consisting of discrete regions

61

Why might exon shuffling happen?

As a result in the evolution of new proteins

62

Information and Translation

Genetic information flows from mRNA to protein through Translation

63

How does cell translate an mRNA message into a protein'?

With the help of transfer RNA (tRNA)

64

tRNAs transfer what?

Transfer amino acids to the growing polypeptide in a ribosome

65

tRNA carries___

one specific amino acid on one end

66

On the other end of a tRNA, there is...

an anticodon. The anticodon base-pairs with a complementary codon on mRNA

67

tRNA consists of a single RNA strand that is how long?

80 nucleotides long

68

What does a tRNA look like?

A cloverleaf

69

Translation requires how many steps?

Two

70

Translation Step 1

a correct match between a tRNA & an amino acid, done by the enzyme aminoacyl-tRNA synthetase

71

Translation Step 2

a correct match between the tRNA anticodon & an mRNA codon

72

What is a wobble?

Flexible pairing at the third base of a codon that allows some tRNAs to bind to more than one codon

73

Ribosomes facilitate specific coupling of

tRNA anticodons with mRNA codons in protein synthesis

74

Two ribosomal subunits are made of

ribosomal proteins (~ 80) and ribosomal RNAs (18S, 5S, 5.8S, 28S)

75

Ribosome has how many binding sites for tRNA?

Three

76

What are the three binding sites that a ribosome has for tRNA?

P, A, and E site

77

P Site

holds the tRNA that carries the growing polypeptide chain

78

A Site

holds the tRNA that carries the next amino acid to be added to the chain

79

E Site

is the exit site, where discharged tRNAs leave the ribosome

80

Three stages of Translation?

Initation, Elongation, Termination

81

Translation ; Initation brings together..

mRNA, a tRNA with the first amino acid, and the two ribosomal subunits

82

What happens first in Initation in Translation?

a small ribosomal subunit binds with mRNA and a special initiator tRNA (met) Then the small subunit moves along the mRNA until it reaches the start codon (AUG)

83

Proteins called initation factors bring...

in the large subunit that completes the translation initiation complex

84

Translation; During Elongation..

amino acids are added oneby one to the C-terminus of the growing chain

85

Translation; Elongation; Each addition invovles proteins called

elongation factors and occurs in 3 steps: codon recognition, peptide bond formation, and translocation

86

When does energy expenditure occur in Elongation (Translation?

During Codon Recognition and Translocation

87

Translation proceeds along the mRNA in a

5' --> 3' direction

88

Termination; Translation

Occurs when a stop codon in the mRNA reaches the A site of the ribosome

89

(Termination; Translation) A site accepts..

A protein called a release factor

90

(Termination; Translation) Release factor causes..

the addition of a water molecule instead of an amino acid

91

(Termination; Translation) The release factor reaction

releases the polypeptide, and the translation assembly comes apart

92

IS translation suffcient to make a functional protein?

Often times no

93

Polypeptide chains are modified after..

translation or targeted to specific sites in the cell

94

Post-Translational Modification, During Synthesis, polypeptide chain begins to..

coil & fold spontaneously to form a protein with a specific 3-D/4-D structure

95

Post-Translational Modifications may be required before...

the protein can begin doing its particular job in the cell

96

What two populations of ribosomes are evident in cells?

Free Ribosomes (Cytosol) and Bound Ribosomes (Attached to ER)

97

Free ribosomes mostly..

synthesize proteins that function in the cytosol

98

Bound ribosomes make..

proteins of the endomembrane system and proteins that are secreted from the cell

99

Ribosomes are identical and..

can switch from free to bound

100

Where does polypeptide synthesis always begin?

In the cytosol

101

Synthesis finishes in ___ unless _______

the cytosol unless the polypeptide signals the ribosome to attach to the ER

102

Polypeptides are destined for

the ER or for secretion are marked by a signal peptide

103

A Signal-Recognition Particle (SRP)

binds to the signal peptide

104

SRP brings...

the signal peptide and its ribosome to the ER

105

Polypeptide Formation (1)

Polypeptide synthesis begins

106

Polypeptide Formation (2)

SRP bings to signal peptide

107

Polypeptide Formation (3)

SRP binds to receptor protein

108

Polypeptide Formation (4)

SRP detaches and polypeptide synthesis resumes

109

Polypeptide Formation (5)

Signal-cleaving enzyme cuts off signal peptide

110

Polypeptide Formation (6)

Completed polypeptide folds into final conformation

111

How is a polyribosome (or polysome) formed?

Multiple ribosomes can translate a singla mRNA simultaneously to form this

112

Polyribosomes enable a cell to..

make many copies of a polypeptide very quickly

113

A bacterial cell ensures astreamlined process by...

coupling transcription and translation

114

What are mutations?

changes in the genetic material of a cell or virus

115

What are point mutations?

chemical changes in just 1 base pair of a gene

116

Change in a single nucleotide in a DNA template strand can lead to..

PRoduction of an abnormal protein (sickle cell anemia)

117

Two categories of Point Mutations

Nucleotide-Pair Substitutions
One or more nucleotide-pair insertions or deletions

118

Nucleotide-Pair Substitution

replaces one nucleotide and its partner with another pair of nucleotides

119

Silent Mutations

have no effect on the amino acid produced by a codon because of redundancy in the genetic code

120

Missense Mutations

still code for an amino acid, but not the correct amino acid

121

Nonsense Mutations

change an amino acid codon into a stop codon, nearly always leading to a nonfunctional protein

122

What are insertions and deletions?

Are additions or losses of nucleotide pairs in a gene

123

Frameshift Mutation

Result after the Insertion or deletion of nucleotides may alter the reading frame,

124

What are Mutagens?

Physical or chemical agents that can cause mutations

125

Structural Gene

a region of DNA that can be expressed to produce a final functional product (part of a physical structure within cell) that is either a polypeptide or an RNA molecule (rRNA, tRNA).

126

Regulatory Gene

regulates the expression of one or more structural genes by regulating the production of a protein which regulates the rate of transcription.