Translation and the role of tRNA

Question 1

Translation

Answer 1

conversion of information in mRNA to protein

Question 2

genetic code

Answer 2

rules by which nt sequence of gene (via mRNA intermediate) is translated into an amino acid sequence of a protein

Question 3

only 4 nucleotides

Answer 3

specify 20 amino acids

Question 4

Triplet code

Answer 4

mRNA sequence decoded in sets of 3 nucleotides

Question 5

Transcription RNA

Answer 5

cell cannot directly translate genes into amino acids intermediate

Question 6

The genetic instructions for a polypeptide chain are written in

Answer 6

the DNA as series of 3 nucleotide words

Question 7

Codon

Answer 7

each group of 3 consecutive nucleotides (triplet) in RNA

Question 8

Sequence of nts in mRNA is read

Answer 8

consecutively codon by codon

Question 9

RNA is a linear polymer

Answer 9

made up of 4 different nts, there are therefore 4 x 4 x 4= 64 possible combinations of 3 nts (i.e. 64 codons)

Question 10

Only 20 different AAs

Answer 10

therefore code is redundant and some AAs are specified by more than one codon

Question 11

Codon specifies either

Answer 11

one amino acid or a stop to the translation process (stop codon)

Question 12

Codons are

Answer 12

adjacent (not overlapping) and not separate by punctuation (comma-less)

Question 13

In principle, an RNA sequence can be read

Answer 13

in any one of the 3 different non-overlapping reading-frames

Question 14

Only one of the 3 possible reading frames

Answer 14

encodes the required protein

Question 15

A punctuation signal at beginning of each RNA message

Answer 15

sets correct reading frame

Question 16

Start codons

Answer 16

indicated by AUG sequence and codes for Methionine amino acid

Question 17

Stop codons

Answer 17

indicated by UAA, UAG, UGA sequence and do not code for an amino acid

Question 18

The RNA codon sequences in the ‘non overlapping reading frames’

Answer 18

to be translated into a protein is known as an ‘open reading frame’ (ORF) and does not contain a stop codon

Question 19

the protein that codes RNA

Answer 19

mRNA

Question 20

Other sub-types of RNA are classified as

Answer 20

non-coding RNA (ncRNA)

Question 21

These subtypes of RNA are also

Answer 21

transcribed from genes on DNA (just not translated into a protein) and they function as RNA molecules

Question 22

There is a gene for every

Answer 22

sub-type of RNA and these genes are transcribed (not translated) and are functional as a nucleic acid

Question 23

3 different types of RNA molecules involved in process of translation

Answer 23

1. mRNA: messenger RNA carries to message from DNA to code for a protein = coding RNA
2. tRNA: Transfer RNA: interprets the message on mRNA and brings the correct amino acid in translation
3. rRNA: ribosomal RNA constitutes part of the ribosomal structure which facilitates the process

Question 24

snRNA

Answer 24

constituent of the SNURPS in the spliceosome (U1, U2, U4, U5, U6) in the process of RNA splicing (RNA processing)

Question 25

mRNA, tRNA and ribosomes

Answer 25

are critical for translation

Question 26

Translation

Answer 26

cell interprets genetic message (RNA) and builds a polypeptide accordingly with amino acids (protein)

Question 27

transfer RNA (tRNA)

Answer 27

The genetic message is a series of codons along an mRNA molecule (the messenger), and the interpreter

Question 28

tRNA transfers amino acids

Answer 28

from cytoplasmic pool of amino acids to a ribosome

Question 29

Ribosome adds each amino acid

Answer 29

brought to it by tRNA to the growing end of a polypeptide chain

Question 30

Therefore the tRNA and Ribosome are

Answer 30

the most crucial molecules to carry out the process of translation on mRNA

Question 31

Translation of mRNA molecules into proteins depends on

Answer 31

tRNAs that can recognise and bind to both codon and AA

Question 32

tRNA molecule consists of a single RNA strand

Answer 32

that is only about 80 nucleotides long

Question 33

Atypical nucleotides on tRNA

Answer 33

D loop = D = dihydrouridine T loop = The TiC-loop = pseudouracil (i)

Question 34

4 short segments of folded tRNA base-pair with each other forming

Answer 34

double helical regions, producing molecule that looks like a cloverleaf (2D)

Question 35

cloverleaf undergoes further folding to form

Answer 35

a compact L-shaped structure (3D)

Question 36

2 key regions of unpaired nts situated

Answer 36

at either end of L-shaped molecule are crucial to function of tRNA in protein synthesis

Question 37

Anticodon

Answer 37

set of 3 consecutive nts that pairs with complementary codon in an mRNA molecule

Question 38

Amino acid binding site

Answer 38

short single-stranded region at 3' end of tRNA: site where AA that matches the codon is attached to tRNA

Question 39

Recognition and attachment of correct AA to tRNA depends on enzymes

Answer 39

aminoacyl-tRNA synthetases that covalently couple each AA to its appropriate set of tRNA molecules

Question 40

20 different aminoacyl-tRNA synthetases

Answer 40

one for each amino acid (x20)

Question 41

All active tRNA must contain CCA sequence on

Answer 41

3' end of tRNA as the recognition site for amino acid treatment

Question 42

ATP is used to

Answer 42

link the amino acid to the correct tRNA producing a high energy bond therefore tRNAs become 'charged' after linkage

Question 43

Example 1

Answer 43

Tryptophan AA is coded for by UGG codon on mRNA. Therefore the tRNA with corresponding ACC anticodon is selected by tryptophanyl tRNA synthase and matches tryptophan AA to 3' end of tRNA

Question 44

Example 2

Answer 44

Tyrosine is coded by UAU codon on mRNA. Therefore tRNA with AUA anticodon selected by Tyrosyl tRNA synthase and matches Tyrosine AA to 3'end of tRNA

Question 45

steps

Answer 45

1: The tRNA and its cognate amino acid enter the active site of the specific synthetase 2: Using ATP, the synthetase catalyses the covalent bonding between the amino acid and the tRNA 3: The tRNA charged with the amino acid is released by the synthetase

Question 46

Accurate translation go genetic message requires. recognition steps in key sites of tRNA

Answer 46

Step 1: Must be a correct match between a tRNA and an amino acid -A tRNA that binds to an mRNA codon specifying a particular amino acid must carry only that amino acid -Each amino acid is joined to the correct tRNA by a specific aminoacyl-tRNA synthetases Step 2: Must be a correct match between the tRNA anticodon and an mRNA codon -Ribosomes facilitate the specific coupling of tRNA anticodons with mRNA codons during protein synthesis