Transfer and Ribosomal RNAs (G) DUMB B

Question 1

What are transfer RNAs and ribosomal RNAs encoded by?

Answer 1

Genes

Question 2

What are tRNAs and rRNAs trasncribed as?

Answer 2

Single-stranded RNAs

Question 3

Are tRNAs and rRNAs linear molecules?

Answer 3

No
Instead, a considerable amount of base pairing occurs within the RNA strand

Question 4

What does base pairing within the RNA strand allow tRNAs and rRNAs to do?

Answer 4

It allows them to fold into specific conformations that are required for their function

Question 5

What is the typical length of tRNAs?

Answer 5

70-90 nucleotides in length

Question 6

How many different tRNAs are there?

Answer 6

At least 20

Question 7

What is each tRNA encoded by?

Answer 7

Its own gene

Question 8

What does tRNA contain a high propoteion of?

Answer 8

It contains a high proportion of nucleotides that have nonstandard bases found only in tRNAs

Question 9

How are nonstandard bases made?

Answer 9

By bse modification after transcription is completed

Question 10

How many regions on tRNA are important for its function in translation?

Answer 10

Two regions

Question 11

What is the anticodon sequence on tRNA?

Answer 11

It is a region important for translation
It is complementary to a particular codon and can pair with that codon

Question 12

What is the importance of the 3’ end of a tRNA?

Answer 12

It is the second important region for translation
It can be covalently linked to an amino acid

Question 13

What are tRNAs with the same anticodon linked to?

Answer 13

They are always linked to the same amino acid specified by the codon that is complementary to the anti codon

Question 14

What is a tRNA linked to an amino acid called?

Answer 14

An aminoacyl-tRNA

Question 15

What enzyme creates a covalent link between a tRNA and the appropriate amino acid?

Answer 15

Aminoacyl-tRNA synthetase

Question 16

How many aminoacyl-tRNA synthetases are there?

Answer 16

There are 20, one for each amino acid

Question 17

Each aminoacyl-tRNA synthetase has a specific name. If the amino acid leucine is attached to a tRNA, what is the enzyme called?

Answer 17

Leucyl-tRNA synthetase

Question 18

What is the process of charging?

Answer 18

A process by which an amino acid is attached to a tRNA

Question 19

What does a charged tRNA contain?

Answer 19

It contains an amino acid

Question 20

What is a tRNA without an attached amino acid called?

Answer 20

An uncharged or empty tRNA

Question 21

What is the ratio of tRNAs and codons? What does that mean?

Answer 21

There are far fewer tRNAs than codons
This means that some tRNAs can pair with more than one codon

Question 22

ughghhghihi wobble stuff

Question 23

What are rRNAs a major component of?

Answer 23

Ribosomes

Question 24

What does a ribosome do with mRNA and aminoacyl-tRNAs?

Answer 24

It brings both of them together and catalyzes the formation of peptide bonds between amino acids

Question 25

What is a ribosome made up of?

Answer 25

Both proteins and rRNAs/

Question 26

How many polypeptides are in each ribosome?

Answer 26

Over 50 polypeptides called ribosomal proteins and 3-4 different rRNA molecules

Question 27

What is each ribosome made out of?

Answer 27

Two parts that interact with one another to carry out translation One large subunit One small subunit

Question 28

What unit of measurement is used for ribosome size?

Answer 28

Svedberg (S) units

Question 29

How big are bacterial ribosomes?

Answer 29

70S Small subunit = 30S Large subunit = 50S

Question 30

How big are eukaryotic ribosomes?

Answer 30

80S Small subunit = 40S Large subunit = 60S

Question 31

Are Svedberg units additive?

Answer 31

No, because it is not a measure of mass

Question 32

How many sites on ribosomes are capable of attaching to tRNA?

Answer 32

Three

Question 33

What are the three ribosomal sites capable of attaching to tRNA?

Answer 33

E site (Exit) P site (peptidyl) A site (aminoacyl)

Question 34

Where are the E, P, and A sites located? What does that mean?

Answer 34

They are located near one another on the ribosome This means that tRNAs attached to these sites are close to one another

Question 35

Which ribosomal subunit has the ability to attach to mRNA?

Answer 35

The small subunit

Question 36

How is the mRNA positioned for the small subunit?

Answer 36

It is positioned so that the codons are located near the E, P, and A sites for tRNA