Concept explainers
As shown in Figure 14.12, four regions within the trpL mRNA can form stem-loops. Let’s suppose that mutations have been previously identified that prevent the ability of a particular region to form a stem-loop with a complementary region. For example, a region 1 mutant cannot form a 1-2 stem-loop, but it can still form a 2-3 or 3-4 stem-loop. Likewise, a region 4 mutant can form a 1-2 or 2-3 stem-loop but not a 3-4 stem-loop. Under each of the following sets of conditions, would attenuation occur?
A. Region 1 is mutant, tryptophan is high, and translation is not occurring.
B. Region 2 is mutant, tryptophan is low, and translation is occurring.
C. Region 3 is mutant, tryptophan is high, and translation is not occurring.
D. Region 4 is mutant, tryptophan is low, and translation is not occurring.
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Genetics: Analysis and Principles
- "The gene for Receptor Z contains an unknown number of untranslated first exons that are spliced to a common exon 2" - what does it mean if a "first exon" is "spliced to a common exon 2"? Does it mean that Exon 1 is attached to Exon 2, but Exon 1 is not part of the translated protein - similar to the below schematic? mRNA Option 1: [Exon 1a][Exon 2][Exon 3].... mRNA Option 2:[Exon1b][Exon2][Exon 3] mRNA Option 3: [Exon1c][Exon2][Exon 3]arrow_forwardThe asterisk (*) in the diagram below indicates a single base mutation in the 5' splice site of the second intron of a eukaryotic gene. Due to this mutation, the second intron is now not ‘spliced out’ during the splicing process. What are the most likely consequences of this mutation with respect to the size of the pre-mRNA and the size of the mature mRNA? a. The pre-mRNA will be longer and the mature mRNA will be longer. b. The pre-mRNA will be longer and the size of the mature mRNA will not be affected c. The size of the pre-mRNA will not be affected and the mature mRNA will be longer d. The size of the pre-mRNA will not be affected and the size of the mature mRNA will not be affectedarrow_forwardThe Dscam locus in Drosophila melanogaster has 24 exons. Four of these exons are able to undergo alternative splicing. Exon 4 has 12 possible splice variants, exon 6 has 48 variants, exon 9 has 33 variants, and exon 17 has 2 variants. If all splicing combinations are possible, how many different Dscam protein sequences could be encoded by a single allele at this locus?arrow_forward
- When a eukaryotic gene is cut out of genomic DNA, geneticists have discovered that enabling the strands to hydrogen bond allows them to hybridize one of the gene's strands to the mRNA for that gene. How can you tell whether this gene undergoes alternative splicing by comparing the mRNAs that result?arrow_forwardSelect the three post-transcriptional modifications often seen in the processing of mRNA in eukaryotes: Group of answer choices heteroduplex formation; base modification; capping 3'-capping; 5'-poly(A) tail addition; splicing 5'-poly(A) tail addition; insertion of introns; capping removal of exons; insertion of introns; capping 5'-capping; 3'-poly(A) tail addition; splicingarrow_forwardThe mRNA sequence 5' AUG AAA CAG GGA UAA 3' encodes a particular peptide of interest to your research team. You have identified a new alternate allele of the sequence 5' AUG AAG CAG GGA UAA 3'. What type of mutation does this alternate sequence illustrate?arrow_forward
- When scientists cut a eukaryotic gene from genomic DNA, they discovered that enabling the strands to hydrogen bond allows them to hybridize one of the gene's strands to the gene's mRNA. How can you tell whether this gene undergoes alternative splicing by comparing the various mRNAs that result?arrow_forwardHere is a eukaryotic gene. The numbers given are base pairs of exon and intron. How long in bases will the pre mRNA transcript be? Explain briefly. What is the maximum number of amino acids that could make up the protein product from the final mRNA? Explain briefly.arrow_forwardThe following is the only intron sequence of a gene that will be excised during the maturation of the mRNA. But it is not spliced in some tissues, where alternative splicing pattern is seen. Will the amino acid of its protein product following this sequence change? Explain with an example. ATAAGCCAGACTCAGCAarrow_forward
- Consider the following mRNA base sequence 5' CUG-CAC 3' (a) What dipeptide is coded for by this mRNA? (b) What dipeptide is formed if a mutation converts CUG to CUU? (c) What dipeptide is formed if a mutation converts CAC to CGC? (d) What dipeptide is formed if a mutation converts CUG to CUU and CAC to CGC?arrow_forwardThe following represent deoxyribonucleotide sequences in the template strand of DNA: Sequence 1: 5′-CTTTTTTGCCAT-3′ Sequence 2: 5′-ACATCAATAACT-3′ Sequence 3: 5′-TACAAGGGTTCT-3′ (a) For each strand, determine the mRNA sequence that would be derived from transcription. (b) Using Figure 12–7, determine the amino acid sequence that is encoded by these mRNAs. (c) For Sequence 1, what is the sequence of the partner DNA strand?arrow_forwardWhy do promoter mutations cluster at positions −10and −35 as shown in Figure 11-11? Which protein-DNAinteraction is disrupted by these mutations?arrow_forward
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