Exam 2 Translation

Front 1

translation occurs in the ... in association with ...

Back 1

cytoplasm

ribosomes

Front 2

translation is the ... step in protein synthesis and overall gene expression. (... is the first step)

Back 2

2nd

transcription

Front 3

the ... is the set of rules by which information encoded in genetic material (DNA or RNA sequences) is translated into proteins (amino acid sequences) by living cells.

Back 3

genetic code

Front 4

protein alphabet consists of # characters

Back 4

20

Front 5

nucleic acid alphabet consists of only # characters

Back 5

4

Front 6

combinations of 3 nucleotides that encodes for a specific amino acid

Back 6

codons

Front 7

there are # possible codons

most amino acids have #-# possible codons

... and ... have only one codon

3 codons do not enconde for an amino acid. These are called ... codons, which signal the end of translation

Back 7

64
2-4
methionine and tryptophan
stop

Front 8

each codon specifies # AA

Back 8

1

Front 9

some AA are specified by more than one possible codon, called the ... code

Back 9

degenerate

Front 10

When an AA has more than one codon, the codons usually vary in the # base, which allows for ... to occur

Back 10

3rd
wobble

Front 11

The code is almost universal among all living organisms. The big exception is the genetic code used to translate human ... and ...

Back 11

mitochondrial RNA and proteins

Front 12

The code is read beginning from the ... end of mRNA at a specific ... (AUG) and ending at a ... (UAA, UAG, UGA) near the ... end of mRNA

Back 12

5'
start codon
stop codon
3'

Front 13

a change in a single nucleotide in the DNA results in a ... in the mRNA sequence (changing a codon), which could result in an abnormal amino acid sequence

Back 13

single change

Front 14

other mutations (insertions, deletions, frameshift mutations) can cause the ... on the mRNA to shift, causing major changes in protein structure and function.

Back 14

reading frame

Front 15

there are # possible reading frames for mRNA

Back 15

3

Front 16

the 3 components that must come together for translation to occur are ...

Back 16

mRNA
tRNA
ribosome

Front 17

what contains the genetic code?

Back 17

mRNA

Front 18

what transports the appropriate amino acid

Back 18

tRNA

Front 19

what is the translator that brings the nucleotide language and amino acid language together to form a protein?

Back 19

ribosome

Front 20

ribosomes consist of ... and ...

the ... and ... subunits associate only during translation

They bring together ... and specific ... molecules that are "charged with an amino acid"

Back 20

protein and rRNA

large and small

mRNA and tRNA

Front 21

in prokaryotes, the large subunit is ... and the small ones are ... and ...

Back 21

70S
30S 50S

Front 22

in eukaryotes, the large subunit is ... and the small ones are ... and ...

Back 22

80S
40S 60S

Front 23

the 60S subunit is transported by a G protein-dependent transporter called ...

Back 23

Nmd3p

Front 24

once within the ... or ..., the ribosomal subunits specifically associate with each other to help guide the translational process

Back 24

cytoplasm or RER

Front 25

what is a small RNA chain (73-93 nucleotides long) that transfers a specific amino acid to a growing polypeptide chain within a ribosome?

Back 25

transfer RNA (tRNA)

Front 26

what serves as an adaptor, or connector between the mRNA and the AA?

Each type of this can be attached to only one type of AA and only one codon on mRNA (highly specific)

Back 26

tRNA

Front 27

the 5' end of the tRNA nucleotide strand usually ends with a ...

Back 27

G

Front 28

the 3' end of the tRNA usually consists of the nucleotide sequence ...

Back 28

CCA-3'

Front 29

amino acids are attached to tRNA at the ... end

Back 29

3'

Front 30

in the 3-D structure of tRNA, you will find a ... loop near the 5' end, a ... loop near the 3' end, and an ... loop in the middle.

Back 30

D
T
anticodon

Front 31

tRNA contains a triplet sequence called the ... that can base pair to the corresponding 3 base codon on mRNA

Back 31

anticodon

Front 32

what is this?
non-standard base pairing in the 3rd position of the codon.

Back 32

the wobble phenomenon

Front 33

what is this?
-Can hydrogen bond to more than one base in the corresponding codon position.
-One of the many modified bases in tRNA and is especially promiscuous in base pairing.
-can bind with A, U, or C.
-gives flexibility when it comes to translation.

Back 33

inosine

Front 34

... can pair with uracil (in addition to C)

Back 34

Guanosine

Front 35

tRNA that has an amino acid covalently attached to its 3’-end is called an … and is said to be …

Back 35

Aminoacyl-tRNA
“charged”

Front 36

What is the enzyme that is needed to attach an amino acid to its tRNA?

It uses an anticodon of tRNA as a recognition site for attachment of amino acid.

It requires energy (ATP)

Back 36

Aminoacyl-tRNA synthase

Front 37

What is the initiator tRNA?

Back 37

Methionyl-tRNAi ^(met)

Front 38

The first step in initiation involves … for translation

Back 38

Preparing the tRNA

Front 39

Methionyl-tRNAi met forms a pre-initiation complex with … and …

Back 39

Eukaryotic initiation factor 2 (eIF2)
Small (40S) ribosomal subunit

Front 40

The second step in initiation involves … for translation

Back 40

Preparation of mRNA

Front 41

What are the 2 important mRNA initiation factors and where do they bind?

Back 41

-cap binding protein (CBP) or eIF4E
-poly-A binding protein (PABP)
-5’ cap

Front 42

What is this?
-binds 3’-poly-A tail of mRNA
-helps to circularize some mRNAs prior to binding ribosome
-either favors or inhibits initiation

Back 42

Poly-A binding protein (PABP)

Front 43

Steps 3-5 of initiation involves …

Back 43

Bringing mRNA into the ribosome

Front 44

Step 3: The cap recognition complex targets mRNA to the …
(bringing the tRNA and mRNA together)

Back 44

Pre-initiation complex

Front 45

Step 4: the small unit ribosome scans along mRNA for the … (AUG)

Back 45

Start codon

Front 46

Step 5: when … (initiator tRNA) base pairs with AUG codon, … hydrolyzes GTP and initiation factors are released

Back 46

Met-tRNA
eIF2

Front 47

Steps 6-7 of initiation involves preparing the …

Back 47

Ribosome

Front 48

Step 6: … dissociate from small ribosomal subunit and are recycled for further rounds of translation

Back 48

Initiation factors

Front 49

Step 7: … (along with both mRNA and Met-tRNA) binds to …

Back 49

Small ribosomal subunit
Large ribosomal subunit

Front 50

What are the 3 binding sites that are available once the ribosome is complete?

Back 50

P-site (peptidyl)
A-site (aminoacyl)
E-site (exit)

Front 51

The initiation phase of translation is regulated by what 2 proteins?

Back 51

-eIF2 protein (required for formation of the pre-initiation complex)
-eIF4E (mRNA cap binding protein)

Front 52

If …, eIF2 does not bind to tRNAmet and translation does not occur. It can become this and inactivated during times of cellular stress, such as starvation, heat, and viral infections.

Back 52

Phosphorylated

Front 53

The eIF4E initiation factor only becomes activated when it … from the 4E-binding protein.
… (a hormone that stimulates protein synthesis[anabolic]) stimulates phosphorylation of the 4E-binding protein, which releases and … eIF4E allowing it to bind to mRNA and initiate translation

Back 53

Dissociates
Insulin
activates

Front 54

What is the major regulator of the initiation step? (the rate limiting step)

Back 54

eIF2

Front 55

The translation defect, Leukoencephalopathy with Vanishing White Matter (VWM) involves:
-chronic-progressive inherited …, usually occurring during childhood
-rapid deterioration of white matter (myelin) following … or minor … (tissue damage)
-inherited mutations within 2 subunits of the … translation initiation factor resulting in inactivation

Back 55

Degenerative brain disease
Febrile infections or minor head trauma
eIF2B

Front 56

Do prokaryotic and eukaryotic translation differ?

Back 56

Only in the initiation phase

Front 57

What are the 5 ways in which prokaryotic (bacterial) initiation of translation differs from eukaryotic?

Back 57

-ribosomes : 70S (30S+50S)
-formylated Met-tRNA
-only 3 initiation factors needed (IF-1, IF-2, IF-3)
-mRNA is not “capped”
-Shine-Dalgarno sequence is used to recognize the start codon and initiate translation

Front 58

What are the 3 sites in the 80S ribosome complex?

Back 58

-P site
-A site
-E site

Front 59

What site is this?
-where Met-tRNAi met is initially bound and where the growing peptide chain is located

Back 59

P site

Front 60

What is the site where new incoming activated tRNAs bind initially?

Back 60

A site

Front 61

What is the site where tRNAs exit the ribosome after they have transferred their amino acid to the growing peptide chain?

Back 61

E site

Front 62

What is the first step of elongation?

Back 62

Binding of aminoacyl-tRNA to the A Site on the ribosome

Front 63

During the first step of elongation:
-incoming aminoacyl-tRNA first combines with elongation factor … + GTP

Back 63

EF1α

Front 64

During the first step of elongation:
-aminoacyl-tRNA-EF1α-GTP complex binds to A site, where GTP is … and EF1α-GDP … from the tRNA

Back 64

Hydrolyzed
Dissociates

Front 65

During the 1st step of elongation:
… of the A site to ensure that each tRNA anticodon matches mRNA codon

Back 65

Proofreading

Front 66

The second step of elongation is …

Back 66

The formation of peptide bonds

Front 67

During the 2nd step of elongation:

-amino acid on tRNA in the … site forms peptide bond with amino acid on tRNA in … site

-catalyzed by … (part of the rRNA of the large ribosomal subunit)

Back 67

A
P

Peptidyltransferase

Front 68

The third step of elongation is…

Back 68

Translocation

Front 69

Translocation involves …
-complexes bind with GTP and binds ribosome
-binding causes … in ribosome that moves mRNA and paired tRNA
-uncharged tRNA moves from P site to the E site and is released from ribosome

Back 69

Elongation factor (EF2)
Conformational change

Front 70

Termination of translation:
-3 steps of elongation repeated until … moves into the A site
-… (a specific protein) binds to ribosome when a … is encountered on the mRNA, causing … to hydrolyze bond between peptide chain and tRNA
-nascent peptide is realsed from the ribosome

Back 70

Stop codon
Release factor
stop codon
peptidyltransferase

Front 71

What is this?
-resembles both transfer and messenger RNA. Stops translation of defective mRNA.

Back 71

tmRNA

Front 72

-Formation of each aminoacyl-tRNA requires # high-energy phosphate bonds in the form of ATP
-formation of the pre-initiation complex requires hydrolysis of …
-during elongation, as each amino acid is added to the growing peptide chain, 2 GTP’s are hydrolyzed (one with …, one with …)

Back 72

2
GTP
EF1, EF2

Front 73

What is this?
-a complex of many ribosomes simultaneously translating a single mRNA
-ribosomes every # nucleotides
-one mRNA guides synthesis of several copies of its protein product

Back 73

Polysomes
100

Front 74

What are these?
-macrolides
-tetracycline
-aminoglycosides

Back 74

Antibiotics that target prokaryotic initiation and ribosomal units

Front 75

MELAS (stands for mitochondrial Myopathy, Encephalopathy, Lactic Acidosis, and Stroke-like episodes)
-involves defective mitochondrial …
-defects include impaired termination, impaired pre-tRNA processing, decreased stability and aminoacylation, and abnormal tRNA conformation
-commonly leads to a decreased steady-state level of normal aminoacylated tRNA, which in turn leads to …
-symptoms: seizures, stroke-like episodes, autonomic dysfunction, headache
-some symptoms mimic Herpes Simplex Encephalitis (HSE)
-defining feature: … or … lactic acid levels are typically high

Back 75

tRNA Leu
reduced protein synthesis
plasma or CSF

Front 76

Hypertension and other cardiovascular diseases
-mutations found in one family involving …
-abnormal mitochondrial proteins normally containing …
-overall effect: high blood …, low blood …

Back 76

-mitochondrial tRNA for isoleucine
-isoleucine
-pressure, magnesium levels

Front 77

What are 2 examples of mutations in mitochondrial tRNA?

Back 77

-MELAS
-Hypertension and other cardiovascular diseases

Front 78

What are 3 examples of diseases caused by premature termination codons in mRNA (PTC mutations)

Back 78

-Duchenne muscular dystrophy
-cystic fibrosis
-cancer

Front 79

# of all inherited diseases result from premature termination codon (PTC) mutations

Back 79

1/3

Front 80

What disease is this?
-most common X-linked fatal genetic disease
-10-20% of patients carry a nonsense mutation resulting in premature translation termination of the dystrophin protein in muscle cells
-absence of dystrophin permits excess calcium to penetrate the sarcolemma

Back 80

Duchenne muscular dystrophy

Front 81

Cystic fibrosis
-2-5% of patients have … mutations in the cystic fibrosis transmembrane regulator (CFTR) gene

Back 81

Nonsense

Front 82

What disease is this?
-PTC mutations in tumor-suppressor genes

Back 82

Cancer

Front 83

What are 2 major therapeutic approaches to overcome nonsense PTC mutations?

Back 83

Gene therapy
Pharmacological

Front 84

Which treatment of PTC mutations is the treatment of choice due to the potential for targeted repair?

Back 84

Gene therapy

Front 85

Which treatment approach of PTC mutations can modify gene expression and block nonsense-mediated mRNA destruction, without correcting the underlying gene defect?

Back 85

Pharmacological

Front 86

What is this?
-a group of antibiotics that are classically used against certain types of bacteria.
-alters the conformation of rRNA, inducing codon misreading that causes either incorporation of an erroneous amino acid (mis-incorporation) at a sense codon or failure of recognition of the stop codon, leading to translational read-through rather than chain termination

Back 86

Aminoglycosides

Front 87

In prokaryotes, aminoglycosides binds to … rRNA, inducing conformational alignment in the ribosomal decoding center despite codon/anticodon mismatch.
-enables UAA codon to be paried with CUU or GUU tRNA anticodon, promoting polypeptide chain … with glutamate or glutamine

Back 87

16S
elongation

Front 88

What is the only process in translation in which energy is not needed?

Back 88

Termination