Question 1

The majority of genes in mammals encode proteins

Accepted Answer

Most genes in multicellular organisms do not encode proteins. For these non-coding genes, the transcribed RNA is the final product.

Question 2

Which of the following statements about transcription and translation are true? Please select all that apply.

Accepted Answer

In bacteria, as there is no nucleus separating the transcriptional and translational machinery, translation of an mRNA can begin before transcription is finished. In eukaryotes, the mRNA is first transported out of the nucleus and is translated in the cytoplasm. Translation is much more similar between species than transcription. Ribosomal RNA (rRNA) is one of the components of the ribosome, which carries out translation.

Question 3

Put the following events in translation in order.
-tRNA is charged with amino acid

Accepted Answer

Charging tRNA with an amino acid is the first step in the translation process, preparing the tRNA to deliver its amino acid to the growing polypeptide chain in the ribosome.

Question 4

Put the following events in translation in order.
-tRNA interacts with mRNA

Accepted Answer

The answer of Put the following events in translation in...

Question 5

Put the following events in translation in order.
-Peptide bond forms

Accepted Answer

The formation of a peptide bond is the third step in the translation process, following the binding of tRNA to the ribosome and the formation of the initiation complex.

Question 6

Put the following events in translation in order.
-tRNA leaves the ribosome4

Accepted Answer

tRNA leaves the ribosome after the amino acid it was carrying is added to the growing polypeptide chain. This happens in step 4 of the translation process, so D is the correct choice.

Question 7

Match the missing words in the following phrase. [A] on [B], which is held within a tunnel in the [C], base-pairs with [D] on tRNA. The 5' of the anticodon corresponds to the [E] of the codon and the 3' of the anticodon correspond to the [F] of the codon.

Accepted Answer

The answer of Match the missing words in the following...

Question 8

There are 4 different bases and 64 possible codons in the genome, 20 different amino acids, and a large but variable number of tRNA genes (400-500 in mammals). How many aminoacyl synthetase genes are there?

Accepted Answer

The number of aminoacyl synthetase genes is equal to the number of amino acids, which is 20.

Question 9

Match the site in the ribosome to its function.
-Charged tRNA enters the ribosome

Accepted Answer

Charged tRNA enters the ribosome at the aminoacyl (A) site. The growing peptide chain is passed to this tRNA, which is then moved into the peptidyl (P) site as the ribosome and mRNA move along. This tRNA then passes the peptide chain to the incoming tRNA at the A site and is then moved to the exit (E) site and leaves the ribosome.

Question 10

Match the site in the ribosome to its function.
-tRNA holds the growing amino acid chain

Accepted Answer

Charged tRNA enters the ribosome at the aminoacyl (A) site. The growing peptide chain is passed to this tRNA, which is then moved into the peptidyl (P) site as the ribosome and mRNA move along. This tRNA then passes the peptide chain to the incoming tRNA at the A site and is then moved to the exit (E) site and leaves the ribosome.

Question 11

Match the site in the ribosome to its function.
-Uncharged tRNA leaves the ribosome

Accepted Answer

Charged tRNA enters the ribosome at the aminoacyl (A) site. The growing peptide chain is passed to this tRNA, which is then moved into the peptidyl (P) site as the ribosome and mRNA move along. This tRNA then passes the peptide chain to the incoming tRNA at the A site and is then moved to the exit (E) site and leaves the ribosome.

Question 12

Which of the following are characteristics of translation initiation? Please select all that apply.

Accepted Answer

During translation initiation, the initiator codon first arrives at the P site. The first codon, AUG, codes for methionine. The tRNA used for initiation is specific to initiation and does not recognize internal codons. The 5' untranslated region (UTR) is by definition not translated.

Question 13

Which of the following is not true of translation termination?

Accepted Answer

Stop codons do not bind to special tRNA molecules. Instead, they bind to release factor proteins which then trigger the release of the polypeptide from the ribosome.

Question 14

During which stage of translation is translational regulation most likely to occur?

Accepted Answer

Translational regulation most commonly occurs during the initiation stage of translation, when the ribosome is selecting which mRNA to translate and is forming a complex with the initiator tRNA. By regulating the availability or activity of initiation factors, the rate or specificity of translation initiation can be controlled.

Question 15

Iron response proteins (IRPs) are involved in regulating iron levels in the cell through translational regulation. Which of the following statements regarding IRP regulation is untrue?

Accepted Answer

IRP binding to the 5' UTR of ferritin mRNA prevents its translation, while binding to the 3' UTR of transferrin receptor mRNA stabilizes it, promoting translation. IRP binding does not prevent transferrin translation; it prevents ferritin translation when iron is low.

Question 16

The regulation that determines the anterior and posterior ends of a developing Drosophila embryo is primarily ______

Accepted Answer

The regulation that determines the anterior and posterior ends of a developing Drosophila embryo is primarily spatial, as it is based on the differential localization of morphogens such as bicoid and nanos mRNA in the egg. Maternal vs paternal translation is not a factor in this process, and while transcriptional regulation is important for overall development, it does not determine the anterior-posterior axis. Temporal regulation may play a secondary role in axis determination, but is not the primary mechanism.

Question 17

Match the missing words in the following phrase. In developing Drosophila embryos, [A] mRNA is evenly distributed through the embryo whereas [B] mRNA is confined to the posterior pole. Nanos protein binds to hunchback mRNA and represses its transcription. This produces a gradient of Nanos protein in the embryo, with more at the [C] end, and a corresponding gradient of Hunchback protein, with more at the [D] end.

Accepted Answer

The answer of Match the missing words in the following...

Question 18

Fill in the blank. Position 3 in the codon is the least likely to influence which amino acid is encoded and has the weakest base-pair interaction; i.e., the position can _______

Accepted Answer

The answer of Fill in the blank. Position 3 in...

Question 19

AUU, AUC, and AUA all encode isoleucine, but AUA is used only ~10% of the time. Why is this thought to be the case?

Accepted Answer

The answer of AUU, AUC, and AUA all encode isoleucine,...

Question 20

Biochemically similar amino acids are likely to have similar codons. This reduces the chance that a mutation will cause an amino acid to be substituted with a different amino acid.

Accepted Answer

Similar amino acids are likely to have similar codons. This does not reduce the chance that a mutation will result in an amino acid substitution. However, this does increase that chance that any replacement amino acid would be biochemically similar and therefore less likely to have a deleterious effect on the protein.

Quiz 13: Translation: From Nucleic Acids to Amino Acids

The majority of genes in mammals encode proteins

Which of the following statements about transcription and translation are true? Please select all that apply.

Put the following events in translation in order. -tRNA is charged with amino acid

Put the following events in translation in order. -tRNA interacts with mRNA

Put the following events in translation in order. -Peptide bond forms

Put the following events in translation in order. -tRNA leaves the ribosome4

Match the missing words in the following phrase. [A] on [B], which is held within a tunnel in the [C], base-pairs with [D] on tRNA. The 5' of the anticodon corresponds to the [E] of the codon and the 3' of the anticodon correspond to the [F] of the codon.

There are 4 different bases and 64 possible codons in the genome, 20 different amino acids, and a large but variable number of tRNA genes (400-500 in mammals) . How many aminoacyl synthetase genes are there?

Match the site in the ribosome to its function. -Charged tRNA enters the ribosome

Match the site in the ribosome to its function. -tRNA holds the growing amino acid chain

Match the site in the ribosome to its function. -Uncharged tRNA leaves the ribosome

Which of the following are characteristics of translation initiation? Please select all that apply.

Which of the following is not true of translation termination?

During which stage of translation is translational regulation most likely to occur?

Iron response proteins (IRPs) are involved in regulating iron levels in the cell through translational regulation. Which of the following statements regarding IRP regulation is untrue?

The regulation that determines the anterior and posterior ends of a developing Drosophila embryo is primarily ______

Fill in the blank. Position 3 in the codon is the least likely to influence which amino acid is encoded and has the weakest base-pair interaction; i.e., the position can _______

AUU, AUC, and AUA all encode isoleucine, but AUA is used only ~10% of the time. Why is this thought to be the case?

Biochemically similar amino acids are likely to have similar codons. This reduces the chance that a mutation will cause an amino acid to be substituted with a different amino acid.