Translation and the Role of tRNA's

Question 1

Define translation.

Answer 1

The conversion of information in mRNA to protein

Question 2

What is the genetic code?

Answer 2

The rules by which nucleotide sequence of a gene is translated into an amino acid sequence of a protein

Question 3

How is the mRNA sequence decoded?

Answer 3

The mRNA sequence is decoded in sets of 3 nucleotides

Question 4

What is the intermediate between genes and amino acids?

Answer 4

Transcription

Question 5

What is a triplet of nucleotides called?

Answer 5

A codon

Question 6

What does a codon specify?

Answer 6

Either an amino acid or a stop codon

Question 7

What is a stop codon?

Answer 7

A stop to the translation process

Question 8

What sequence of nucleotides acts as a start codon?

Answer 8

AUG

Question 9

What does AUG code for?

Answer 9

Methionine

Question 10

What are the three ways a stop codon can be indicated?

Answer 10

UAA

UAG

UGA

Question 11

What does AUG code for?

Answer 11

A start codon

Question 12

What three RNA molecules are involved in translation?

4

Answer 12

mRNA

tRNA

rRNA

(snRNA - forms spliceosome)

Question 13

In general what happens during translation?

Answer 13

The cell interprets a genetic message and builds a polypeptide accordingly

Question 14

What carries the genetic message?

Answer 14

An mRNA molecule

Question 15

What acts as the interpreter of mRNA?

Answer 15

Transfer RNA

Question 16

What does tRNA do?

Answer 16

tRNA transfers amino acids from cytoplasmic pool of amino acids to a ribosome

Question 17

What do ribosomes do?

Answer 17

They add each amino acid brought to it by tRNA to the growing end of a polypeptide chain

Question 18

What are the two most crucial molecules in translation?

Answer 18

tRNA

Ribosomes

Question 19

What does tRNA have to bind to?

Answer 19

Both a codon and an amino acid

Question 20

What does tRNA consist of?

Answer 20

A single RNA strand

Question 21

How long is tRNA?

Answer 21

About 80 nucleotides long

Question 22

Describe the shape of tRNA.

Answer 22

Looks like a cloverleaf (2D)

Question 23

Describe the 3D shape of tRNA.

Answer 23

L-shaped structure

Question 24

What are the two most crucial regions of tRNA?

Answer 24

Anticodon

Amino acid binding site

Question 25

What is an anticodon?

Answer 25

A set of 3 nucleotides which pairs with a complementary codon in an mRNA molecule

Question 26

What is an amino acid binding site?

2

Answer 26

A short single stranded region at the 3’ end of tRNA site

This is where the amino acid that matches the codon is attached to tRNA

Question 27

What couples tRNAs to their correct amino acid?

Answer 27

Specific enzymes

Question 28

What happens to tRNA when it links to it’s amino acid?

Answer 28

The tRNA becomes ‘charged’

Question 29

What enzymes are responsible for recognition and attachment of correct amino acid by tRNA?

Answer 29

Aminoacyl-tRNA synthetases

Question 30

What are the two recognition steps on key sites of tRNA?

Answer 30

There must be a correct match between a tRNA and an amino acid

Must be a correct match between the tRNA anticodon and an mRNA codon

Question 31

What facilitates the specific coupling of tRNA anticodons with mRNA codons?

Answer 31

Ribosomes

Question 32

What is the main role of ribosomes in translation?

Answer 32

They facilitate the specific coupling of tRNA anticodons with mRNA codons during protein synthesis

Question 33

How many different types of aminoacyl-tRNA synthetases are there?

Answer 33

There are 20 -> one for each amino acid of the genetic code