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Biology > D1.2 (Protein Synthesis) > Flashcards

D1.2 (Protein Synthesis) Flashcards

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1
Q
A
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2
Q

What is transcription?

A

Transcription is the process where the nucleotide base sequence of a section of DNA is used to synthesize an mRNA molecule using complementary base pairing.

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3
Q

Define mRNA.

A

mRNA (messenger RNA) is a single-stranded RNA molecule that transfers genetic information from the DNA in the nucleus to the cytoplasm.

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4
Q

True or False? RNA polymerase is involved in DNA replication.

A

False. RNA polymerase is involved in transcription, not DNA replication.

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5
Q

What happens during the elongation phase of transcription?

A

During elongation, RNA polymerase builds the mRNA molecule by bonding RNA nucleotides together.

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6
Q

Define gene expression.

A

Gene expression is the process by which a gene is ‘switched on’ and undergoes transcription and translation.

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7
Q

True or False? The template strand of DNA is transcribed to form mRNA.

A

True. The template strand of DNA is transcribed to form mRNA.

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8
Q

What is the role of hydrogen bonds in transcription?

A

Hydrogen bonds form between RNA nucleotides and their complementary DNA bases during transcription.

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9
Q

What is the function of RNA polymerase?

A

RNA polymerase is the enzyme responsible for synthesizing mRNA during transcription.

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10
Q

Define complementary base pairing in transcription.

A

Complementary base pairing in transcription is the process where RNA nucleotides pair with their complementary DNA bases.

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11
Q

True or False? The coding strand of DNA is the one that is transcribed during transcription.

A

False. The template strand of DNA is the one that is transcribed during transcription.

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12
Q

Identify the four RNA bases.

A

The four bases in RNA are: Adenine, Uracil, Cytosine, Guanine.

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13
Q

What is a polypeptide?

A

A polypeptide is a chain of amino acids covalently bonded together with peptide bonds.

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14
Q

Define the term codon.

A

A codon is a sequence of three mRNA bases that codes for a specific amino acid.

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15
Q

True or False? Translation occurs in the nucleus.

A

False. Translation occurs in the cytoplasm, transcription occurs in the nucleus.

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16
Q

What role does tRNA play in translation?

A

tRNA binds with specific amino acids and brings them to the mRNA on the ribosome.

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17
Q

What is the function of ribosomal RNA (rRNA)?

A

Ribosomal RNA (rRNA) is part of the ribosome structure and helps catalyse the formation of peptide bonds in proteins.

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18
Q

Define the term anticodon.

A

An anticodon is a sequence of three bases on the tRNA molecule that are complementary to a codon on mRNA.

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19
Q

True or False? The codon GAC on mRNA would pair with the anticodon CTG on tRNA.

A

False. The codon GAC on mRNA would pair with the anticodon CUG on tRNA.

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20
Q

What is the stop codon?

A

A stop codon is a specific sequence of mRNA bases that signals the end of translation.

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21
Q

What happens after the mRNA leaves the nucleus?

A

After leaving the nucleus, the mRNA attaches to a ribosome in the cytoplasm for translation.

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22
Q

State the role of the ribosome during translation.

A

The ribosome facilitates the binding of tRNA to mRNA and catalyses the formation of peptide bonds to synthesize a polypeptide.

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23
Q

Define what is meant by the term ‘triplet code’.

A

A triplet code is a sequence of three DNA nucleotide bases that codes for one amino acid.

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24
Q

True or False? Each amino acid is coded by only one triplet.

A

False. Each amino acid can be coded by multiple triplets, making the genetic code degenerate.

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25
What does the term 'degenerate code' mean?
A degenerate code means that multiple codons can code for the same amino acid.
26
What is the significance of the start codon (TAC)?
The start codon TAC codes for methionine and signals the beginning of a gene in protein synthesis.
27
True or False? The genetic code is universal across all organisms.
True. The genetic code is universal, meaning the same triplets code for the same amino acids in all living organisms.
28
What is the purpose of a stop codon?
A stop codon signals the end of translation, indicating where the polypeptide chain should stop being synthesized.
29
The genetic code is non-overlapping, how does this affect protein synthesis?
The genetic code being non-overlapping means each base is read only once in a single codon, preventing overlap in the sequence interpretation.
30
What is the role of ATP during translation?
ATP provides the energy required for forming peptide bonds between amino acids during translation.
31
Why is it important that the ribosome can bind with more than one tRNA molecule at a time?
Binding with two tRNA molecules at a time allows the formation of a peptide bond between adjacent amino acids to accurately build up the amino acid sequence in the polypeptide chain.
32
What is a gene mutation?
A gene mutation is a change in the sequence of bases in a DNA molecule that may result in a new allele.
33
True or False? Most mutations are beneficial.
False. Most mutations are harmful or neutral (have no effect).
34
Define the term point mutation.
A point mutation is a mutation where one base in the DNA sequence is altered, potentially changing the amino acid at that location.
35
True or False? Mutations in body cells are inherited by offspring.
False. Mutations in body cells are not inherited; only mutations in gametes are passed on to offspring.
36
Define the term allele.
An allele is a variant form of a gene that may result from a mutation and can lead to different traits or conditions.
37
Why do some mutations have no impact on the amino acid sequence or the final polypeptide structure?
As the genetic code is degenerate, a change in nucleotide base sequence may still code for the same amino acid despite being a different codon.
38
What are the three main stages of mRNA synthesis?
The three stages of mRNA synthesis are initiation, elongation, and termination.
39
In which direction does RNA polymerase add nucleotides during elongation?
RNA polymerase adds the 5' end of free RNA nucleotides to the 3' end of the growing mRNA molecule, occurring in the 5' to 3' direction.
40
What triggers the termination of transcription?
Transcription is terminated when RNA polymerase reaches a terminator sequence, which causes the polymerase enzyme and mRNA strand to detach.
41
In which direction is mRNA read during translation?
mRNA is read in the 5' to 3' direction during translation at the ribosome.
42
What is the function of the promoter in transcription?
The promoter is a DNA sequence that acts as the binding site for RNA polymerase to initiate transcription.
43
What is the function of general transcription factors in eukaryotes?
General transcription factors in eukaryotes bind directly to the promoter to help initiate transcription by allowing RNA polymerase to attach.
44
What is the function of non-coding DNA sequences in gene regulation?
Non-coding DNA sequences like enhancers and silencers are involved in the control of gene expression by enhancing or suppressing transcription.
45
What is the role of telomeres in DNA replication?
Telomeres, the repeated sequences at the ends of chromosomes, facilitate the binding of an RNA primer to allow for the synthesis of the final Okazaki fragment during replication.
46
What are the purposes of post-transcriptional modification of mRNA in eukaryotes?
Post-transcriptional modification helps prevent mRNA degradation and increases the efficiency of protein synthesis, as well as expanding the complexity of the proteome.
47
How does post-transcriptional modification differ between prokaryotes and eukaryotes?
Prokaryotic mRNA does not require significant post-transcriptional modification since translation can occur immediately after transcription, while eukaryotic mRNA undergoes several modifications before translation.
48
What are the three main post-transcriptional events that occur in eukaryotes?
The three post-transcriptional events are: Adding a methylated cap to the 5' end, Adding a poly-A tail to the 3' end, Removing non-coding introns and joining the coding exons.
49
What is the difference between exons and introns?
Exons are the coding sequences that are translated into proteins, while introns are the non-coding sequences that are removed during splicing.
50
What happens during the splicing process?
During splicing, the introns (non-coding sections) are removed and the exons (coding sections) are joined together to form the mature mRNA molecule.
51
What is alternative splicing?
Alternative splicing allows different combinations of exons to be included in the final mature mRNA, enabling a single gene to code for multiple protein variants.
52
How does alternative splicing contribute to the size of the proteome?
Alternative splicing is one reason why the proteome, the set of proteins expressed by a genome, is much larger than the genome itself.
53
What is the difference between pre-mRNA and mRNA?
Pre-mRNA is the initial transcript that includes both exons and introns, while mRNA is the mature form that only contains the joined exons after intron removal.
54
What is the purpose of the methylated cap added to eukaryotic mRNA?
The methylated cap is added to the 5' end to protect against degradation by exonucleases.
55
What is the purpose of the poly-A tail added to eukaryotic mRNA?
The poly-A tail (long chain of adenine nucleotides) is added to the 3' end for further protection and to help the transcript exit the nucleus.
56
What are the three tRNA binding sites on a ribosome?
The three tRNA binding sites on a ribosome are the E (exit), P (peptidyl), and A (aminoacyl) sites.
57
What does the A site join with?
At the A site the mRNA codon joins with the tRNA anticodon.
58
What happens at the P site?
At the P site the amino acids attached to the tRNA are joined by peptide bonds.
59
What happens at the E site?
At the E site the tRNA exits the ribosome.
60
What is meant by the term 'modification of polypeptides'?
The polypeptide must be modified post-translation in order to be transformed from the just the primary structure into a functional protein.
61
Name an example of how polypeptides can be modified after translation.
Protein folding is an example of post-translation modification where the primary protein structure is transformed into the secondary, tertiary and quaternary structures.
62
Define the term proteolysis.
Proteolysis is the process of breaking down proteins into their constituent amino acids using enzymes called proteases.
63
What is the function of the proteasome?
The proteasome is an organelle that contains proteases and acts as the location for proteolysis in the cell.
64
What is the purpose of tagging proteins with ubiquitin?
Tagging proteins with ubiquitin begins the process of them being broken down in the proteasome.

Biology (13 decks)

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