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Questions and Answers
The genetic code is said to be triplet, meaning that there ________.
The genetic code is said to be triplet, meaning that there ________.
are three bases in mRNA that code for an amino acid
The code is nonoverlapping, meaning that a given base participates in the specification of one and only one amino acid.
The code is nonoverlapping, meaning that a given base participates in the specification of one and only one amino acid.
True
Both the codons UUU and UUC specify the amino acid phenylalanine. This is possible because the genetic code is __________.
Both the codons UUU and UUC specify the amino acid phenylalanine. This is possible because the genetic code is __________.
degenerate
The genetic code is degenerate, meaning that a codon can specify more than one amino acid.
The genetic code is degenerate, meaning that a codon can specify more than one amino acid.
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What kind of mutation could have occurred if a DNA sequence produces a mutant protein with several differing amino acids?
What kind of mutation could have occurred if a DNA sequence produces a mutant protein with several differing amino acids?
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Which statement about eukaryotic transcription is false?
Which statement about eukaryotic transcription is false?
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What is the initiator triplet in both prokaryotes and eukaryotes? What amino acid is recruited by this triplet?
What is the initiator triplet in both prokaryotes and eukaryotes? What amino acid is recruited by this triplet?
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When examining the genetic code, it is apparent that ________.
When examining the genetic code, it is apparent that ________.
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The relationship between a gene and a messenger RNA is that ________.
The relationship between a gene and a messenger RNA is that ________.
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RNA synthesis from a DNA template is called __________.
RNA synthesis from a DNA template is called __________.
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Which of the following is a common consensus sequence located in the region of the DNA where RNA polymerase(s) bind?
Which of the following is a common consensus sequence located in the region of the DNA where RNA polymerase(s) bind?
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A 3′ poly-A tail and a 5′-cap are common components of prokaryotic RNAs.
A 3′ poly-A tail and a 5′-cap are common components of prokaryotic RNAs.
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A 5′-cap describes the addition of a base, usually thymine, to the 5′ end of a completed peptide.
A 5′-cap describes the addition of a base, usually thymine, to the 5′ end of a completed peptide.
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Which subunit of RNA polymerase establishes template binding to a promoter in prokaryotes?
Which subunit of RNA polymerase establishes template binding to a promoter in prokaryotes?
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Which of the following contains the three posttranscriptional modifications often seen in the maturation of mRNA in eukaryotes?
Which of the following contains the three posttranscriptional modifications often seen in the maturation of mRNA in eukaryotes?
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Transcription factors function to help move ribosomes along the mRNA.
Transcription factors function to help move ribosomes along the mRNA.
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What is a likely cause of the discrepancy between the length of the gene for Duchenne muscular dystrophy and its mRNA?
What is a likely cause of the discrepancy between the length of the gene for Duchenne muscular dystrophy and its mRNA?
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If one compares the base sequences of related genes from different species, one is likely to find that corresponding ________ are usually conserved, but the sequences of ________ are much less well conserved.
If one compares the base sequences of related genes from different species, one is likely to find that corresponding ________ are usually conserved, but the sequences of ________ are much less well conserved.
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What is a characteristic of RNA splicing in eukaryotes?
What is a characteristic of RNA splicing in eukaryotes?
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A snRNP is best described as _______.
A snRNP is best described as _______.
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Study Notes
Genetic Code and Its Characteristics
- The genetic code is defined as triplet, meaning three bases in mRNA correspond to one amino acid.
- The code is non-overlapping, indicating each base specifies only one amino acid.
- Codons UUU and UUC both code for phenylalanine, demonstrating the degeneracy of the genetic code where multiple triplets can specify a single amino acid.
- The degeneracy does not imply a single codon can code for different amino acids; rather, each codon specifies one amino acid.
Mutations and Their Effects
- A mutant protein with several altered amino acids suggests the presence of addition and deletion mutations that affect the reading frame, but can be compensated by another mutation.
Eukaryotic vs. Prokaryotic Transcription
- Polycistronic mRNA, which can encode multiple proteins, occurs only in prokaryotes, whereas eukaryotic mRNA is typically monocistronic, transcribing one gene at a time.
- The initiator triplet for transcription in both prokaryotes and eukaryotes is AUG, which recruits methionine.
RNA Synthesis and Processing
- RNA synthesis from DNA is termed transcription, initiated when genes are expressed.
- Common consensus sequences for RNA polymerase binding include TATA.
- In eukaryotes, transcription is followed by mRNA processing, including the removal of introns, resulting in mRNA that is shorter than the original gene.
Post-Transcriptional Modifications
- Eukaryotic mRNA maturation typically includes heteroduplex formation, base modification, and capping.
- mRNA features include a 3' poly-A tail and a 5' cap, not present in prokaryotic RNAs.
Introns and Exons
- During RNA processing, introns (non-coding regions) are spliced out, while exons (coding sequences) are retained, which helps explain the length discrepancy between the gene and the resulting mRNA.
- Observations of gene sequences across species reveal that exons are conservatively maintained while introns vary more broadly.
RNA Splicing Mechanism
- RNA splicing in eukaryotes involves specific splice junctions: a 5' GU and a 3' AG.
- Small nuclear ribonucleoproteins (snRNPs) are key components of the spliceosome, facilitating the accurate excision of introns and the joining of exons.
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Description
Test your knowledge of transcription in genetics with these flashcards. Each card features key terms and definitions related to the genetic code, codons, and amino acids. Perfect for anyone studying molecular biology principles.
