Ch 22 Translation

Question 1

What is hybridization of ovalbumin DNA and mRNA?

Answer 1

Hybridized DNA and mRNA molecules include large loops of unpaired DNA.

Question 2

What is alternative splicing?

Answer 2

A process where a given gene can generate more than one protein product.

Question 3

Why are humans more complex than organisms like roundworms despite having a comparable number of genes?

Answer 3

Alternative splicing explains the increased complexity.

Question 4

What is the estimated number of protein-coding genes in Homo sapiens?

Answer 4

21,000 protein-coding genes.

Question 5

What is the estimated number of proteins produced by Homo sapiens?

Answer 5

118,400 proteins.

Question 6

What structural feature is added to the 3’-end of mature eukaryotic mRNA?

Answer 6

Polyadenylation (adding a poly-A tail).

Question 7

What occurs in the nucleus of eukaryotic cells?

Answer 7

Transcript capping, polyadenylation, and splicing.

Question 8

What is translation?

Answer 8

The conversion of the genetic code in the mRNA sequence into a polypeptide sequence.

Question 9

What are the steps involved in translation?

Answer 9

Individual amino acids are activated and fused to tRNA molecules, combined with ribosomes and mRNA, and joined to make a polypeptide.

Question 10

What is the adaptor hypothesis?

Answer 10

Proposed by Francis Crick in 1955, it requires mRNA containing codons and tRNA containing an anticodon.

Question 11

What does the 3’ end of tRNA carry?

Answer 11

A specific amino acid.

Question 12

What is the role of the large subunit of the ribosome?

Answer 12

Catalyzes formation of peptide bonds between the growing polypeptide and incoming amino acids.

Question 13

What is the function of tRNA synthetase?

Answer 13

Matches amino acids to tRNA.

Question 14

What is the genetic code?

Answer 14

Read by tRNA molecules in sets of three consecutive nucleotides in mRNA called a codon.

Question 15

What does each codon specify?

Answer 15

One particular amino acid used in making the protein.

Question 16

What is the significance of the reading frame in translation?

Answer 16

A given nucleotide sequence in mRNA can potentially have three different reading frames.

Question 17

What are stop codons?

Answer 17

UAA, UAG, UGA.

Question 18

What is ‘wobble’ in the context of codon-anticodon pairing?

Answer 18

Adaptable hydrogen bonding that allows non-traditional base-pairing.

Question 19

What is the Shine-Dalgarno sequence?

Answer 19

A purine-rich leader segment that acts as a ribosomal binding site in prokaryotes.

Question 20

What is required for chain initiation in prokaryotes?

Answer 20

fmet-tRNA, initiation codon (AUG), ribosome binding site, 30S and 50S ribosomal subunits, initiation factors, GTP, and Mg2+.

Question 21

What is the role of elongation factors in translation elongation?

Answer 21

Facilitate the binding of aminoacyl-tRNAs and the movement of tRNAs through the ribosome.

Question 22

What is the peptidyl transferase reaction?

Answer 22

Catalyzes the formation of peptide bonds during translation.

Question 23

What happens during translation termination in E. coli?

Answer 23

A ribosome recycling factor prepares the ribosome for another round of translation.

Question 24

What binds to EF-Tu with approximately the same affinity?

Answer 24

All aminoacyl–tRNAs

This indicates that the binding affinity does not vary significantly among different aminoacyl–tRNAs.

Question 25

What is the responsibility of the ribosome recycling factor in bacteria?

Answer 25

Preparing the ribosome for another round of translation ## Footnote This factor is crucial for reusing ribosomes after a translation cycle.

Question 26

What are the components required for amino acid activation?

Answer 26

* Amino acids * tRNAs * ATP * Mg2+ ## Footnote These components are necessary to activate amino acids before they are incorporated into proteins.

Question 27

What components are needed for chain initiation in translation?

Answer 27

* fmet-tRNAfmet * initiation codon (AUG) * 30S and 50S ribosomal subunits * GTP * Mg2+ * initiation factors (IF-1, IF-2, and IF-3) ## Footnote This step initiates the protein synthesis process by assembling the translation machinery.

Question 28

What components are involved in chain elongation during translation?

Answer 28

* 70S ribosome * codons of mRNA * GTP * Mg2+ * elongation factors (EF-Tu, EF-Ts, and EF-G) * aminoacyl-tRNAs ## Footnote This phase involves the addition of amino acids to the growing polypeptide chain.

Question 29

What components are required for chain termination in translation?

Answer 29

* 70S ribosome * termination codons (UAA, UAG, or UGA) * release factors (RF-1, RF-2, or RF-3) * GTP * Mg2+ * aminoacyl-tRNA synthetases ## Footnote This step concludes protein synthesis and releases the newly formed polypeptide.