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Biology HL - IB > Protein synthesis > Flashcards

Protein synthesis Flashcards

1
Q

What is transcription in the context of protein synthesis?

A

Transcription is the process of synthesizing RNA from a DNA template.

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2
Q

Which enzyme is primarily responsible for transcription?

A

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

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3
Q

What is the role of RNA polymerase in transcription?

A

RNA polymerase binds to the DNA template, unwinds the double helix, and synthesizes a complementary RNA strand.

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4
Q

How does RNA polymerase initiate transcription?

A

RNA polymerase binds to a specific region called the promoter on the DNA template to start transcription.

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5
Q

What direction does RNA polymerase synthesize RNA?

A

RNA polymerase synthesizes RNA in the 5’ to 3’ direction.

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6
Q

What happens to the DNA strands during transcription?

A

The DNA strands temporarily unwind and separate to allow access to the template strand for RNA synthesis.

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7
Q

What is the significance of complementary base pairing in transcription?

A

Complementary base pairing ensures that the correct RNA nucleotides are added according to the DNA template (A with U, C with G).

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8
Q

What type of RNA is produced during transcription?

A

Messenger RNA (mRNA) is produced during transcription, which carries genetic information from DNA to ribosomes.

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9
Q

How does transcription terminate?

A

Transcription terminates when RNA polymerase reaches a termination signal in the DNA sequence, resulting in the release of the newly synthesized RNA molecule.

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10
Q

Why is transcription an essential step in protein synthesis?

A

Transcription is essential because it converts genetic information from DNA into a form (mRNA) that can be translated into proteins.

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11
Q

What is the role of complementary base pairing in transcription?

A

Complementary base pairing ensures that RNA nucleotides are added correctly to the growing RNA strand based on the DNA template.

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12
Q

Which base pairs with adenine (A) on the DNA template during transcription?

A

Uracil (U) pairs with adenine (A) on the RNA strand.

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13
Q

How does hydrogen bonding facilitate transcription?

A

Hydrogen bonds form between complementary bases (A-U and C-G), stabilizing the RNA-DNA hybrid during RNA synthesis.

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14
Q

What is the significance of the A-U pairing in RNA synthesis?

A

The A-U pairing allows for the correct incorporation of nucleotides, ensuring accurate transcription of genetic information.

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15
Q

What happens to hydrogen bonds after RNA synthesis is complete?

A

After RNA synthesis, the hydrogen bonds between the RNA and DNA strands break, allowing the newly synthesized RNA to detach.

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16
Q

Why is accurate base pairing important during transcription?

A

Accurate base pairing is crucial for producing a faithful copy of the genetic information encoded in DNA.

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17
Q

How do hydrogen bonds compare in strength to covalent bonds?

A

Hydrogen bonds are weaker than covalent bonds, allowing for temporary interactions necessary for processes like transcription.

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18
Q

What role does RNA polymerase play in relation to base pairing?

A

RNA polymerase facilitates the binding of RNA nucleotides to the DNA template, ensuring proper base pairing during transcription.

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19
Q

How does complementary base pairing contribute to the overall fidelity of gene expression?

A

By ensuring that each RNA molecule is an accurate copy of its corresponding DNA sequence, complementary base pairing enhances gene expression fidelity.

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20
Q

In what way does understanding hydrogen bonding and base pairing aid in molecular biology?

A

Understanding these concepts provides insight into the mechanisms of gene expression and regulation, which are fundamental to cellular function and development.

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21
Q

What is the role of single DNA strands during transcription?

A

Single DNA strands serve as templates for transcribing a base sequence into RNA without changing the DNA base sequence.

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22
Q

Why is the stability of DNA templates important in somatic cells?

A

Stability is crucial because the DNA sequences must be conserved throughout the life of a cell, especially in non-dividing somatic cells.

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23
Q

How does the stability of DNA templates contribute to cellular function?

A

Stable DNA templates ensure that genetic information remains intact for accurate protein synthesis and cellular processes.

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24
Q

What happens to the DNA template during transcription?

A

The DNA template remains unchanged while RNA is synthesized based on its sequence.

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25
Q

Why is it essential for the DNA base sequence to be conserved?

A

Conserving the DNA base sequence ensures that genetic information can be reliably passed on during cell division and maintained in daughter cells.

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26
Q

How does complementary base pairing relate to the stability of DNA templates?

A

Complementary base pairing between nucleotides helps maintain the integrity and stability of the DNA structure during transcription.

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27
Q

What are the consequences if DNA sequences are not stable in somatic cells?

A

Instability can lead to mutations, which may disrupt normal cellular functions and contribute to diseases, including cancer.

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28
Q

In what type of cells is the conservation of DNA sequences particularly critical?

A

Conservation is particularly critical in somatic cells that do not divide, as these cells rely on stable genetic information for their functions.

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29
Q

How does RNA synthesis affect the original DNA template?

A

RNA synthesis does not alter the original DNA template; it merely uses it as a guide to produce a complementary RNA strand.

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30
Q

Why is understanding the stability of DNA templates significant in molecular biology?

A

Understanding this stability is essential for grasping how genetic information is preserved and expressed, which underlies all biological processes.

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31
Q

What is transcription in relation to gene expression?

A

Transcription is the first stage of gene expression, where RNA is synthesized from a DNA template.

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32
Q

Why is transcription considered a key stage in gene expression?

A

Transcription is crucial because it determines whether a gene is expressed by producing the corresponding RNA molecule.

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33
Q

Are all genes expressed at the same time in a cell?

A

No, not all genes in a cell are expressed at any given time; gene expression can be regulated based on cellular needs.

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34
Q

How can the expression of a gene be switched on or off?

A

The expression of a gene can be controlled at the transcription level by regulating the activity of RNA polymerase and the availability of transcription factors.

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35
Q

What role do transcription factors play in gene expression?

A

Transcription factors bind to specific DNA sequences to enhance or inhibit the binding of RNA polymerase, thereby regulating transcription.

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36
Q

What happens to a gene that is not transcribed?

A

If a gene is not transcribed, it will not produce mRNA, and consequently, no protein will be synthesized from that gene.

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37
Q

Why is understanding transcription important in molecular biology?

A

Understanding transcription is essential for grasping how genes are regulated and how cells respond to internal and external signals.

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38
Q

How does transcription relate to cellular differentiation?

A

Transcriptional regulation allows different cell types to express specific sets of genes, leading to cellular differentiation and specialized functions.

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39
Q

What can affect the rate of transcription for a particular gene?

A

Factors such as the presence of enhancers, silencers, and the overall chromatin structure can influence the rate of transcription.

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40
Q

How does transcription initiate in eukaryotic cells?

A

In eukaryotic cells, transcription initiates when RNA polymerase binds to the promoter region of a gene with the help of transcription factors.

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41
Q

What is translation in the context of protein synthesis?

A

Translation is the process of synthesizing polypeptides (proteins) from the base sequence of mRNA.

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42
Q

How does the base sequence of mRNA relate to the amino acid sequence of a polypeptide?

A

The base sequence of mRNA is translated into a specific sequence of amino acids, forming a polypeptide.

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43
Q

What is the role of ribosomes in translation?

A

Ribosomes facilitate the decoding of mRNA and the assembly of amino acids into polypeptides.

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44
Q

What are codons in mRNA?

A

Codons are sequences of three nucleotides in mRNA that specify a particular amino acid.

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45
Q

How does tRNA contribute to translation?

A

Transfer RNA (tRNA) carries specific amino acids to the ribosome and matches them to the corresponding codons on the mRNA.

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46
Q

What is the significance of the start codon in translation?

A

The start codon (AUG) signals the beginning of translation and codes for the amino acid methionine.

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47
Q

What happens during the elongation phase of translation?

A

During elongation, tRNAs bring amino acids to the ribosome, which links them together to form a growing polypeptide chain.

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48
Q

How does termination occur in translation?

A

Termination occurs when a stop codon (UAA, UAG, or UGA) is reached, signaling the end of polypeptide synthesis and releasing the completed protein.

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49
Q

Why is understanding translation important in molecular biology?

A

Understanding translation is crucial for comprehending how genetic information is expressed as functional proteins, which are essential for all cellular processes.

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50
Q

What role do post-translational modifications play after translation?

A

Post-translational modifications can alter protein function, stability, and localization, influencing how proteins perform their roles in cells.

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51
Q

What is the role of mRNA in translation?

A

mRNA carries the genetic information from DNA and serves as a template for synthesizing polypeptides.

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52
Q

How does mRNA bind to the ribosome during translation?

A

mRNA binds to the small subunit of the ribosome, allowing for proper alignment during protein synthesis

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53
Q

What is the function of ribosomes in translation?

A

Ribosomes facilitate the decoding of mRNA and the assembly of amino acids into a polypeptide chain.

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54
Q

What are the two subunits of a ribosome?

A

The ribosome consists of a small subunit and a large subunit, which work together during translation.

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55
Q

How many tRNAs can bind simultaneously to the large subunit of the ribosome?

A

Two tRNAs can bind simultaneously to the large subunit of the ribosome during translation.

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56
Q

What is the role of tRNA in translation?

A

tRNA transports specific amino acids to the ribosome and matches them to the corresponding codons on the mRNA.

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57
Q

How does tRNA recognize codons on mRNA?

A

Each tRNA has an anticodon region that is complementary to a specific codon on the mRNA, allowing for accurate pairing.

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58
Q

What happens when a tRNA binds to its corresponding codon on mRNA?

A

When a tRNA binds to its codon, it brings its attached amino acid to the ribosome for incorporation into the growing polypeptide chain.

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59
Q

Why is it important for mRNA, tRNA, and ribosomes to work together in translation?

A

Their collaboration ensures that genetic information is accurately translated into functional proteins, essential for cellular processes.

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60
Q

What is the significance of understanding the roles of mRNA, ribosomes, and tRNA in molecular biology?

A

Understanding these roles provides insight into how proteins are synthesized, which is fundamental to all biological functions and processes.

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61
Q

What is the role of tRNA in translation?

A

tRNA carries specific amino acids to the ribosome and matches them to the corresponding codons on the mRNA.

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62
Q

What are codons in the context of mRNA?

A

Codons are sequences of three nucleotides in mRNA that specify a particular amino acid.

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63
Q

What are anticodons in tRNA?

A

Anticodons are sequences of three nucleotides in tRNA that are complementary to specific codons on the mRNA.

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64
Q

How do codons and anticodons interact during translation?

A

Codons on the mRNA pair with complementary anticodons on the tRNA, ensuring the correct amino acid is added to the growing polypeptide chain.

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65
Q

What is the significance of complementary base pairing between tRNA and mRNA?

A

Complementary base pairing ensures accurate translation of genetic information from mRNA into a specific sequence of amino acids.

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66
Q

How does the pairing between codons and anticodons contribute to protein synthesis?

A

The pairing allows for the correct incorporation of amino acids, which determines the structure and function of the resulting protein.

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67
Q

What happens if there is a mismatch between a codon and an anticodon?

A

A mismatch can lead to the incorporation of an incorrect amino acid, potentially resulting in a nonfunctional or malfunctioning protein.

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68
Q

Why is it important for tRNA to have a specific anticodon for each amino acid?

A

Each tRNA molecule must have a specific anticodon to ensure that it brings the correct amino acid corresponding to its codon on the mRNA.

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69
Q

How does the ribosome facilitate the interaction between tRNA and mRNA?

A

The ribosome provides a site where mRNA codons and tRNA anticodons can align, allowing for efficient translation.

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70
Q

Why is understanding complementary base pairing between tRNA and mRNA important in molecular biology?

A

Understanding this interaction is crucial for comprehending how genetic information is translated into functional proteins, which are vital for all biological processes.

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71
Q

What is the genetic code?

A

The genetic code is a set of rules that defines how the sequence of nucleotides in mRNA is translated into the amino acid sequence of a polypeptide.

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72
Q

Why is the genetic code referred to as a triplet code?

A

The genetic code is a triplet code because each amino acid is specified by a sequence of three nucleotides (a codon) in mRNA.

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73
Q

What are codons?

A

Codons are sequences of three nucleotides in mRNA that correspond to specific amino acids or stop signals during translation.

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74
Q

What does “degeneracy” mean in the context of the genetic code?

A

Degeneracy refers to the fact that multiple codons can code for the same amino acid, providing redundancy in the genetic code.

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75
Q

Why is degeneracy important for protein synthesis?

A

Degeneracy helps minimize the impact of mutations by allowing some changes in the DNA sequence to not affect the resulting protein.

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76
Q

What does “universality” mean regarding the genetic code?

A

Universality means that the genetic code is nearly the same across all living organisms, indicating a common evolutionary origin.

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77
Q

How does universality affect our understanding of genetics?

A

The universality of the genetic code allows for gene transfer between different species, enabling advancements in biotechnology and medicine.

78
Q

Can you give an example of codon degeneracy?

A

For example, both UUU and UUC codons specify the amino acid phenylalanine, demonstrating degeneracy in the genetic code.

79
Q

What is a stop codon?

A

A stop codon is a specific codon (UAA, UAG, or UGA) that signals the termination of protein synthesis during translation.

80
Q

Why is it significant to understand features of the genetic code in molecular biology?

A

Understanding these features provides insight into how genes are expressed and regulated, which is fundamental for studying genetics, evolution, and biotechnology.

81
Q

What is the purpose of using the genetic code table?

A

The genetic code table is used to deduce the sequence of amino acids coded by an mRNA strand.

82
Q

How is the mRNA sequence read in translation?

A

The mRNA sequence is read in groups of three nucleotides called codons.

83
Q

What is a codon?

A

A codon is a sequence of three nucleotides in mRNA that corresponds to a specific amino acid.

84
Q

How do you determine the amino acid sequence from an mRNA strand?

A

By using the genetic code table, match each codon from the mRNA to its corresponding amino acid.

85
Q

What does it mean if a codon is not present in the genetic code table?

A

If a codon is not present, it may be a stop codon, which signals the termination of translation.

86
Q

Can you give an example of how to read an mRNA sequence?

A

For example, if the mRNA sequence is AUG-CCG-GUA, you would look up each codon (AUG, CCG, GUA) in the genetic code table to find the corresponding amino acids.

87
Q

What does the start codon (AUG) signify?

A

The start codon (AUG) signifies the beginning of translation and codes for the amino acid methionine

88
Q

Why is it important to understand how to use the genetic code table?

A

Understanding how to use the genetic code table is essential for predicting protein sequences and studying gene expression.

89
Q

What role do stop codons play in translation?

A

Stop codons signal the end of polypeptide synthesis, instructing the ribosome to release the completed protein.

90
Q

How does degeneracy relate to using the genetic code table?

A

Degeneracy means that multiple codons can specify the same amino acid, allowing for redundancy in coding and minimizing potential errors during translation.

91
Q

What is the role of the ribosome during translation?

A

The ribosome facilitates the stepwise movement along mRNA and catalyzes the linkage of amino acids to form a polypeptide chain.

92
Q

How does the ribosome move along the mRNA strand during translation?

A

The ribosome moves along the mRNA in a 5’ to 3’ direction, reading the codons sequentially.

93
Q

What occurs during the elongation phase of translation?

A

During elongation, tRNAs bring amino acids to the ribosome, which links them together through peptide bonds to form a growing polypeptide chain.

94
Q

How does a peptide bond form between amino acids?

A

A peptide bond forms through a dehydration reaction, where a molecule of water is released as the carboxyl group of one amino acid reacts with the amino group of another.

95
Q

What is the significance of the ribosomal A site?

A

The A site (aminoacyl site) is where incoming tRNA carrying an amino acid binds to the ribosome during elongation.

96
Q

What happens at the P site of the ribosome?

A

The P site (peptidyl site) holds the tRNA with the growing polypeptide chain, facilitating peptide bond formation with the amino acid from the A site.

97
Q

What occurs after a peptide bond is formed?

A

After a peptide bond is formed, the ribosome translocates, shifting its position along the mRNA to allow new tRNA to enter at the A site.

98
Q

How many amino acids can be linked together during translation?

A

Amino acids can be linked together indefinitely, forming polypeptides until a stop codon is reached on the mRNA.

99
Q

What role do elongation factors play in translation?

A

Elongation factors assist in the recruitment of tRNAs and promote translocation, ensuring efficient polypeptide synthesis.

100
Q

Why is understanding the stepwise movement of the ribosome important in molecular biology?

A

Understanding this process provides insight into how proteins are synthesized, which is fundamental for cellular function and regulation in all living organisms.

101
Q

What is a mutation in the context of genetics?

A

A mutation is a change in the nucleotide sequence of DNA that can affect the structure and function of proteins.

102
Q

How can mutations impact protein structure?

A

Mutations can lead to changes in the amino acid sequence of a protein, potentially altering its structure and function.

103
Q

What is a point mutation?

A

A point mutation is a type of mutation where a single nucleotide is substituted, inserted, or deleted in the DNA sequence.

104
Q

How does a point mutation affect protein synthesis?

A

A point mutation can change one codon in mRNA, leading to the incorporation of a different amino acid in the polypeptide chain.

105
Q

What is an example of a point mutation affecting protein structure?

A

Sickle cell disease is caused by a point mutation in the hemoglobin gene, where adenine (A) is replaced with thymine (T), resulting in valine instead of glutamic acid.

106
Q

How does the sickle cell mutation affect hemoglobin?

A

The substitution of valine for glutamic acid causes hemoglobin molecules to aggregate, leading to distorted red blood cells and reduced oxygen-carrying capacity.

107
Q

What are the potential consequences of mutations on protein function?

A

Mutations can lead to loss of function, gain of function, or altered function of proteins, which may result in diseases or physiological changes.

108
Q

What is a silent mutation?

A

A silent mutation is a type of point mutation that does not change the amino acid sequence due to redundancy in the genetic code.

109
Q

How do missense mutations differ from nonsense mutations?

A

Missense mutations result in a different amino acid being incorporated into the protein, while nonsense mutations create a premature stop codon, truncating the protein.

110
Q

Why is understanding mutations important in molecular biology?

A

Understanding mutations helps explain genetic diversity, disease mechanisms, and the basis for certain genetic disorders, which is crucial for research and medical advancements.

111
Q

What does “5’ to 3’” mean in the context of transcription?

A

“5’ to 3’” indicates the direction in which RNA is synthesized during transcription, meaning nucleotides are added to the 3’ end of the growing RNA strand.

112
Q

How does RNA polymerase facilitate transcription?

A

RNA polymerase synthesizes RNA by adding ribonucleotides in a 5’ to 3’ direction, using the DNA template strand.

113
Q

What is the significance of the 5’ and 3’ ends of nucleic acids?

A

The 5’ end has a phosphate group, while the 3’ end has a hydroxyl group, which determines the directionality of synthesis during transcription and translation.

114
Q

What does “5’ to 3’” mean in the context of translation?

A

“5’ to 3’” refers to the direction in which mRNA is read by the ribosome during translation, allowing for codons to be decoded sequentially.

115
Q

How does the ribosome move along mRNA during translation?

A

The ribosome moves along the mRNA strand from the 5’ end to the 3’ end, reading codons and facilitating amino acid addition.

116
Q

Why is it important for transcription and translation to occur in a specific direction?

A

The specific directionality ensures proper alignment of nucleotides and amino acids, leading to accurate protein synthesis.

117
Q

What is the role of tRNA in relation to directionality during translation?

A

tRNA molecules bring amino acids to the ribosome in accordance with mRNA codons, aligning their anticodons with codons in a 5’ to 3’ manner.

118
Q

How does understanding directionality contribute to molecular biology?

A

Understanding directionality is crucial for comprehending how genetic information is expressed and regulated, which underlies all biological processes.

119
Q

What happens if there is a mistake in reading mRNA during translation?

A

A mistake can lead to incorrect amino acid incorporation, potentially resulting in a nonfunctional or malfunctioning protein.

120
Q

Why is it essential for students to grasp the concept of directionality in transcription and translation?

A

Grasping this concept is fundamental for understanding gene expression mechanisms and how proteins are synthesized accurately within cells.

121
Q

What is the promoter in the context of transcription?

A

The promoter is a specific DNA sequence that signals the start site for transcription and where RNA polymerase binds to initiate RNA synthesis.

122
Q

What role do transcription factors play in the initiation of transcription?

A

Transcription factors are proteins that bind to the promoter region, facilitating the recruitment of RNA polymerase to initiate transcription.

123
Q

How does RNA polymerase recognize the promoter?

A

RNA polymerase recognizes the promoter through specific sequences and interactions with transcription factors that help position it correctly.

124
Q

What happens once RNA polymerase is bound to the promoter?

A

Once bound, RNA polymerase unwinds the DNA double helix and begins synthesizing RNA from the DNA template strand.

125
Q

Why is the binding of transcription factors critical for transcription initiation?

A

The binding of transcription factors is critical because it ensures that RNA polymerase is properly positioned to start transcription at the correct location.

126
Q

Can you explain the concept of “enhancers” in relation to promoters?

A

Enhancers are regulatory DNA sequences that can increase transcription levels by facilitating additional binding of transcription factors, enhancing RNA polymerase activity at the promoter.

127
Q

What is a key difference between prokaryotic and eukaryotic promoters?

A

Eukaryotic promoters often have more complex regulatory elements and require multiple transcription factors, while prokaryotic promoters are generally simpler and directly recognized by RNA polymerase.

128
Q

How does the structure of DNA change during the initiation phase of transcription?

A

During initiation, RNA polymerase unwinds a small section of the DNA double helix, creating a transcription bubble where RNA synthesis occurs.

129
Q

What is the significance of understanding transcription initiation in molecular biology?

A

Understanding transcription initiation is essential for grasping how genes are regulated and expressed, which has implications for development, disease, and biotechnology.

130
Q

What occurs after successful initiation of transcription at the promoter?

A

After successful initiation, RNA polymerase begins elongating the RNA strand by adding complementary ribonucleotides based on the DNA template.

131
Q

What are non-coding sequences in DNA?

A

Non-coding sequences are regions of DNA that do not code for polypeptides and have various regulatory and structural functions.

132
Q

What is the role of regulatory sequences in gene expression?

A

Regulatory sequences control the timing and level of gene expression by binding transcription factors and other proteins.

133
Q

What are introns?

A

Introns are non-coding segments of a gene that are transcribed into RNA but are removed during RNA processing before translation.

134
Q

How do introns affect gene expression?

A

Introns can play roles in alternative splicing, allowing a single gene to produce multiple protein isoforms by including or excluding specific exons.

135
Q

What are telomeres?

A

Telomeres are repetitive non-coding sequences at the ends of chromosomes that protect them from degradation and prevent fusion with neighboring chromosomes.

136
Q

Why are telomeres important for cellular aging?

A

Telomeres shorten with each cell division, and when they become too short, they trigger cellular senescence or apoptosis, limiting the number of divisions a cell can undergo.

137
Q

What is the function of genes for rRNA (ribosomal RNA)?

A

Genes for rRNA code for RNA molecules that form the structural and functional components of ribosomes, essential for protein synthesis.

138
Q

What is the function of genes for tRNA (transfer RNA)?

A

Genes for tRNA code for RNA molecules that transport specific amino acids to the ribosome during translation, matching them to corresponding codons on mRNA.

139
Q

How do non-coding sequences contribute to genetic diversity?

A

Non-coding sequences can influence gene regulation and alternative splicing, contributing to variability in protein production and function.

140
Q

Why is it important to study non-coding sequences in molecular biology?

A

Understanding non-coding sequences is crucial for comprehending gene regulation, cellular functions, and the complexities of genetic diseases and evolution.

141
Q

What is post-transcriptional modification?

A

Post-transcriptional modification refers to the processes that occur to mRNA after transcription but before translation, ensuring the mRNA is mature and functional.

142
Q

What happens to introns during post-transcriptional modification?

A

Introns are non-coding sequences that are removed from the pre-mRNA during RNA processing.

143
Q

What is splicing?

A

Splicing is the process of joining together exons (coding sequences) after introns have been removed, resulting in mature mRNA.

144
Q

Why is splicing important for mRNA?

A

Splicing is crucial because it ensures that only the coding sequences (exons) are included in the final mRNA, allowing for accurate translation into protein.

145
Q

What are 5’ caps?

A

A 5’ cap is a modified guanine nucleotide added to the 5’ end of the mRNA molecule, which protects the mRNA from degradation and aids in ribosome binding during translation.

146
Q

What is a polyA tail?

A

A polyA tail is a sequence of adenine nucleotides added to the 3’ end of the mRNA, which enhances stability and facilitates export from the nucleus.

147
Q

How do 5’ caps and polyA tails contribute to mRNA stability?

A

Both modifications protect mRNA from enzymatic degradation and enhance its stability, allowing for efficient translation.

148
Q

What occurs during the transition from pre-mRNA to mature mRNA?

A

The transition includes removal of introns, splicing of exons, addition of a 5’ cap, and addition of a polyA tail.

149
Q

Why is understanding post-transcriptional modification important in molecular biology?

A

Understanding these modifications is essential for comprehending how gene expression is regulated and how proteins are accurately synthesized in eukaryotic cells.

150
Q

What can happen if post-transcriptional modifications do not occur properly?

A

Improper modifications can lead to unstable or nonfunctional mRNA, resulting in incorrect protein synthesis and potential cellular dysfunction or disease.

151
Q

What is alternative splicing?

A

Alternative splicing is a process that allows different combinations of exons to be joined together, resulting in the production of multiple protein variants from a single gene.

152
Q

How does alternative splicing contribute to protein diversity?

A

By splicing exons in various combinations, alternative splicing enables a single gene to code for different polypeptides, increasing the diversity of proteins produced.

153
Q

What are exons?

A

Exons are the coding sequences of a gene that remain in the mature mRNA after introns are removed during post-transcriptional modification.

154
Q

Why is alternative splicing important for eukaryotic organisms?

A

Alternative splicing allows for greater complexity and adaptability in protein function, enabling organisms to respond to varying environmental conditions and developmental needs.

155
Q

What role does the spliceosome play in alternative splicing?

A

The spliceosome is a complex of proteins and RNA that facilitates the removal of introns and the joining of exons during mRNA processing.

156
Q

How does alternative splicing affect gene regulation?

A

Alternative splicing can regulate gene expression by producing different protein isoforms that may have distinct functions or regulatory roles in the cell.

157
Q

What is the significance of understanding alternative splicing in molecular biology?

A

Understanding alternative splicing is crucial for comprehending how genes can produce multiple functional proteins, which has implications for development, evolution, and disease.

158
Q

Can alternative splicing occur in all genes?

A

No, not all genes undergo alternative splicing; it primarily occurs in eukaryotic genes and is more common in genes with multiple exons.

159
Q

How can mutations affect alternative splicing?

A

Mutations in splice sites or regulatory elements can disrupt normal splicing patterns, potentially leading to the production of dysfunctional proteins or diseases.

160
Q

What is the potential impact of alternative splicing on therapeutic approaches?

A

Understanding alternative splicing can inform therapeutic strategies by targeting specific protein isoforms involved in diseases, allowing for more precise treatments.

161
Q

What is the first step in the initiation of translation?

A

The first step is the attachment of the small ribosomal subunit to the 5’ terminal of the mRNA molecule.

162
Q

How does the small ribosomal subunit locate the start codon?

A

The small ribosomal subunit scans along the mRNA until it finds the start codon (AUG).

163
Q

What is the role of the initiator tRNA during initiation?

A

The initiator tRNA carries the amino acid methionine and binds to the start codon on the mRNA at the ribosome.

164
Q

What happens after the initiator tRNA binds to the start codon?

A

Another tRNA, corresponding to the next codon on the mRNA, binds to the A site of the ribosome.

165
Q

What are the three binding sites for tRNA on the ribosome?

A

The three binding sites are A (aminoacyl), P (peptidyl), and E (exit) sites.

166
Q

What occurs at the A site during elongation?

A

The A site is where a new tRNA carrying an amino acid binds, matching its anticodon with the corresponding mRNA codon.

167
Q

What happens at the P site?

A

The P site holds the tRNA that carries the growing polypeptide chain, facilitating peptide bond formation with the amino acid at the A site.

168
Q

What is the function of the E site?

A

The E site is where empty tRNAs exit from the ribosome after their amino acids have been added to the polypeptide chain.

169
Q

How does the large ribosomal subunit contribute to translation initiation?

A

The large ribosomal subunit attaches to the small subunit after initiation, completing the functional ribosome and allowing for peptide bond formation during elongation.

170
Q

Why is understanding initiation of translation important in molecular biology?

A

Understanding initiation is crucial for comprehending how proteins are synthesized, which is fundamental for cellular function and regulation in all living organisms.

171
Q

What is the significance of post-translational modification?

A

Post-translational modification is essential for converting polypeptides into their functional forms, allowing them to perform their biological roles.

172
Q

What is pre-proinsulin?

A

Pre-proinsulin is the initial form of insulin synthesized as a polypeptide that undergoes modifications to become active insulin.

173
Q

What are the two main stages of modification from pre-proinsulin to insulin?

A

The two main stages are the removal of the signal peptide and the cleavage of proinsulin to form active insulin.

174
Q

How does pre-proinsulin become proinsulin?

A

The signal peptide is removed from pre-proinsulin during its entry into the endoplasmic reticulum, producing proinsulin.

175
Q

What happens to proinsulin during its conversion to insulin?

A

Proinsulin is cleaved by specific enzymes, removing connecting peptide sequences (C-peptides) to form active insulin.

176
Q

Why is it important for insulin to be properly modified?

A

Proper modification ensures that insulin can effectively regulate glucose levels in the body, impacting metabolism and energy homeostasis.

177
Q

What are some other common types of post-translational modifications besides cleavage?

A

Other common modifications include phosphorylation, glycosylation, methylation, and ubiquitination, which can affect protein function and stability.

178
Q

How do modifications affect protein activity?

A

Modifications can alter protein conformation, localization, stability, and interactions with other molecules, influencing overall activity.

179
Q

What role do chaperone proteins play in polypeptide modification?

A

Chaperone proteins assist in the proper folding of polypeptides into their functional three-dimensional structures during modification.

180
Q

Why is understanding polypeptide modification important in molecular biology?

A

Understanding these processes is crucial for comprehending how proteins function in cellular processes and how dysregulation can lead to diseases.

181
Q

What is the role of proteasomes in the cell?

A

Proteasomes are protein complexes that degrade unneeded, damaged, or misfolded proteins, recycling amino acids for new protein synthesis.

182
Q

Why is the recycling of amino acids important for cellular function?

A

Recycling amino acids is essential for sustaining a functional proteome, allowing cells to maintain a balance between protein synthesis and degradation.

183
Q

What happens to proteins targeted for degradation?

A

Proteins destined for degradation are tagged with ubiquitin, marking them for recognition and breakdown by the proteasome.

184
Q

How do proteasomes recognize proteins for degradation?

A

Proteasomes recognize ubiquitin-tagged proteins and unfold them before translocating them into their catalytic core for degradation.

185
Q

What is the outcome of protein degradation by proteasomes?

A

The degradation process results in the breakdown of proteins into smaller peptides and free amino acids, which can be reused by the cell.

186
Q

How does protein turnover contribute to cellular homeostasis?

A

Protein turnover ensures that damaged or unnecessary proteins are removed, allowing cells to adapt to changing conditions and maintain proper function.

187
Q

What is the relationship between protein synthesis and degradation?

A

A balance between protein synthesis and degradation is crucial for maintaining cellular health and function, as it regulates the levels of specific proteins.

188
Q

How does the proteasome pathway differ from lysosomal degradation?

A

The proteasome pathway specifically targets ubiquitinated proteins for degradation, while lysosomal degradation involves engulfing larger cellular debris or organelles.

189
Q

Why is understanding proteasome function important in molecular biology?

A

Understanding proteasome function provides insights into cellular regulation, protein quality control, and potential therapeutic targets for diseases related to protein misfolding.

190
Q

What can happen if the proteasome system is dysfunctional?

A

Dysfunction in the proteasome system can lead to the accumulation of damaged proteins, contributing to various diseases, including neurodegenerative disorders and cancer.

Biology HL - IB (29 decks)

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