The DNA sequence below gives the first 12 base pairs of the transcribed region of a gene, and the template and nontemplate strands of DNA are identified. The transcription start is the thymine nucleotide at the end of the sequence given. Use the diagram to answer the list of questions. Make a copy of the diagram before you begin answering the questions, or have one group member diagram the answers for bacteria and another group member diagram the answers for eukaryotes.
Nontemplate strand _____ TTGCTACGGTCA_
Template strand _ AACGATGCCAGT_____
Assuming the sequence shown is part of a eukaryotic gene, what consensus sequence(s) would you expect to identify within about 100 base pairs of the start of transcription?

검증된 단계별 안내

Identify the transcription start site, which is the thymine nucleotide at the end of the sequence provided. This is the +1 position, and transcription begins here.

Understand that in eukaryotic genes, consensus sequences are regulatory elements found near the transcription start site. These sequences help recruit transcription machinery. The most common consensus sequences are the TATA box (around -25 to -30 base pairs upstream) and the CAAT box (around -75 base pairs upstream).

Examine the nontemplate strand sequence provided (TTGCTACGGTCA) and consider the upstream region (approximately 100 base pairs before the transcription start site). Look for sequences that resemble the TATA box (TATAAA) or the CAAT box (GGCCAATCT).

If no exact matches for the TATA box or CAAT box are found, consider that variations in these sequences are common. Look for sequences that are similar to the consensus sequences, as they may still function as regulatory elements.

Conclude that the presence of these consensus sequences (or their variants) within 100 base pairs upstream of the transcription start site is expected in eukaryotic genes, as they play a critical role in initiating transcription by recruiting RNA polymerase and other transcription factors.

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주요 개념

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Transcription in Eukaryotes

Transcription in eukaryotes involves the synthesis of RNA from a DNA template, occurring in the nucleus. It begins at a specific site called the promoter, which is recognized by RNA polymerase and associated transcription factors. The process includes several steps: initiation, elongation, and termination, with the pre-mRNA undergoing further processing, such as capping and splicing, before becoming mature mRNA.

Consensus Sequences

Consensus sequences are short, recurring patterns in DNA that are crucial for the binding of transcription factors and RNA polymerase. These sequences are typically found in promoter regions and can include elements like the TATA box and other regulatory motifs. Identifying these sequences helps predict where transcription will initiate and is essential for understanding gene regulation.

Template and Nontemplate Strands

In DNA, the template strand is the strand that RNA polymerase reads to synthesize RNA, while the nontemplate strand, also known as the coding strand, has the same sequence as the RNA (except for thymine being replaced by uracil). Understanding the roles of these strands is vital for interpreting the direction of transcription and the resulting RNA sequence, which is essential for answering questions about gene expression.

관련 실천

교과서 질문

Genomic DNA from a mouse is isolated, fragmented, and denatured into single strands. It is then mixed with mRNA isolated from the cytoplasm of mouse cells. The image represents an electron micrograph result showing the hybridization of single-stranded DNA and mRNA.

Which nucleic acid is indicated by the 'b' pointer? Justify your answer.

559

views

교과서 질문

The DNA sequence below gives the first 12 base pairs of the transcribed region of a gene, and the template and nontemplate strands of DNA are identified. The transcription start is the thymine nucleotide at the end of the sequence given. Use the diagram to answer the list of questions. Make a copy of the diagram before you begin answering the questions, or have one group member diagram the answers for bacteria and another group member diagram the answers for eukaryotes. Nontemplate strand ___________TTGCTACGGTCA___________

Template strand ___________AACGATGCCAGT___________

Write the anticipated bacterial consensus sequence(s) in the approximate position(s) on the diagram.

515

views

교과서 질문

Nontemplate strand ___________ TTGCTACGGTCA___________

Template strand ___________ AACGATGCCAGT___________

Write the anticipated eukaryotic consensus sequence(s) in the approximate position(s) on the diagram.

456

views

교과서 질문

Which nucleic acid is indicated by the 'a' pointer? Justify your answer.