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Ch.26 Nucleic Acids and Protein Synthesis
McMurry - Fundamentals of GOB 8th Edition
McMurry8th EditionFundamentals of GOBISBN: 9780134015187Not the one you use?Change textbook
All textbooksMcMurry 8th EditionCh.26 Nucleic Acids and Protein SynthesisProblem 14
Chapter 26, Problem 14

What is the function of the spliceosome in hnRNA?

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1
Understand that hnRNA (heterogeneous nuclear RNA) is the precursor to mRNA (messenger RNA) in eukaryotic cells. It contains both exons (coding regions) and introns (non-coding regions).
Recognize that the spliceosome is a large molecular complex made up of proteins and small nuclear RNAs (snRNAs). Its primary function is to process hnRNA by removing introns and joining exons together.
Learn that the spliceosome identifies specific sequences at the intron-exon boundaries, such as the 5' splice site, the branch point, and the 3' splice site, to accurately perform splicing.
Understand that the spliceosome catalyzes two transesterification reactions: the first cuts the 5' splice site and forms a lariat structure with the branch point, and the second cuts the 3' splice site and joins the exons together.
Realize that the final product of this process is mature mRNA, which is ready for translation into a protein. The spliceosome ensures that only the necessary coding sequences are retained in the mRNA.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Spliceosome

The spliceosome is a complex molecular machine found in the nucleus of eukaryotic cells. It is responsible for the splicing of pre-messenger RNA (hnRNA), which involves the removal of non-coding sequences (introns) and the joining of coding sequences (exons). This process is crucial for the maturation of hnRNA into functional mRNA, which can then be translated into proteins.
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Processing of Pre-mRNA Example 1

hnRNA (Heterogeneous Nuclear RNA)

Heterogeneous nuclear RNA (hnRNA) refers to the primary transcript of eukaryotic genes, which includes both exons and introns. hnRNA is initially synthesized from DNA and undergoes several processing steps, including capping, polyadenylation, and splicing, to become mature mRNA. Understanding hnRNA is essential for grasping how gene expression is regulated at the RNA level.
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RNA Splicing

RNA splicing is the process by which introns are removed from hnRNA and exons are joined together to form a continuous coding sequence. This process is facilitated by the spliceosome and is vital for generating mature mRNA that accurately reflects the coding information of the gene. Proper splicing is crucial for the correct expression of genes and the production of functional proteins.
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Related Practice
Textbook Question

DNA and RNA, like proteins, can be denatured to produce unfolded or uncoiled strands. Heating DNA to what is referred to as its “melting temperature” denatures it (the two strands of the double helix become separated). Why does a longer strand of DNA have a higher melting temperature than a shorter one?

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Textbook Question

What are Okazaki fragments? What role do they serve in DNA metabolism?

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Textbook Question

What is the difference between DNA polymerase and DNA ligase?

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Textbook Question

What mRNA base sequences are complementary to the following DNA template sequences? Be sure to label the 5′ and 3′ ends of the complementary sequences.

a. 5′ CAT GCT CTA CAG 3′

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Textbook Question

List possible codon sequences for the following amino acids.

a. Val

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Textbook Question

Identify the amino acid for which the codon GAG codes, and what other codon could encode for this same amino acid?

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