Biology Chapter 14 Flashcards
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Questions and Answers

Using the image, determine the total number of exons contained in the unknown gene.

6

Using the image, determine the total number of introns contained in the unknown gene.

5

Why is a cap added to mRNA, but not to tRNA or rRNA?

Each of the three types of RNA are transcribed by different RNA polymerases. Only RNA polymerase II, involved in mRNA synthesis, contains a domain capable of interacting with enzymes that form the cap.

What is the function of the spliceosome?

<p>The spliceosome removes the introns and joins the exons to form the mature transcript.</p> Signup and view all the answers

In eukaryotic gene regulation, RNA interference occurs through?

<p>The action of microRNAs that block the translation of specific mRNA molecules.</p> Signup and view all the answers

Explain why the hybrid gene mRNA transcript does not undergo 3' cleavage and polyadenylation.

<p>Regulatory factors must first associate with RNA polymerase II before 3' cleavage and polyadenylation.</p> Signup and view all the answers

Where is the most likely location of the 5' untranslated region on the DNA and RNA molecule?

<p>Exon 1</p> Signup and view all the answers

Where would the 3' untranslated region be located on the DNA and RNA molecule?

<p>Exon 8</p> Signup and view all the answers

Classify each description as true of introns only, true of exons only, or true of both introns and exons.

<p>Code for an amino acid sequence &amp; Part of the final mRNA strand</p> Signup and view all the answers

What are the true statements regarding mRNA splicing?

<p>TRUE: splicing occurs while the mRNA is attached to spliceosome, small RNAs in the spliceosome recognize the 5' and 3' splice sites, one mRNA can code for more than one protein by splicing at alternative sites. FALSE: in splicing, exon sequences are removed in the form of lariat formation and are degraded, splicing occurs after it enters the cytoplasm but before it binds to the ribosome.</p> Signup and view all the answers

Label the structural features of the yeast phenylalanine tRNA.

<p>Yellow: region that carries the amino acid at its end; Purple: 5' end; Green: region that contains the bases ribouridine and pseudouridine; Orange: Extra arm; Red: region that contains the base dihydrourdine; Black: region that contains the anticodon, which base pairs with the mRNA.</p> Signup and view all the answers

Assign the RNA regulation consequences to the type of deletion most likely to result in the consequence.

<p>5' cap deletion: introns are not removed from the pre-mRNA</p> Signup and view all the answers

Select the best explanation for how overexpression of CHS silences expression of CHS.

<p>CHS overexpression increases concentration of CHS mRNA in the cytosol, which activates an RNA-induced silencing complex that degrades mRNA or suppresses its translation.</p> Signup and view all the answers

Match each pre-mRNA processing function with its appropriate type.

<p>Addition of poly(A) tail: Assists mRNA in binding to the large ribosomal subunit</p> Signup and view all the answers

Identify the true statements about RNA interference.

<p>Duplex RNA (dsRNA) can suppress the expression of a gene, miRNAs are short, single strands approximately 21 nucleotides long, Small RNAs interfere with gene expression by interacting with mRNA, bringing about mRNA degradation.</p> Signup and view all the answers

What does it mean for bacterial genes to be colinear?

<p>The number of nucleotides in a gene should be proportional to the number of amino acids in the protein encoded by that gene.</p> Signup and view all the answers

One purpose of the 5' untranslated region of mRNA is _____?

<p>To bind to ribosomes.</p> Signup and view all the answers

The most abundant form of RNA inside the cell is _____ RNA.

<p>Ribosomal.</p> Signup and view all the answers

Inhibition of gene expression triggered by double-stranded RNA molecules is termed RNA ____.

<p>Interference.</p> Signup and view all the answers

Which statement correctly describes the critical observation that disproved rRNA as the intermediary molecule?

<p>The ribosomes isolated after switching the phage-infected bacterial cells to grow in a medium containing lighter radioisotope only contained the original heavy radioisotopes (15N and 13C).</p> Signup and view all the answers

Which site does not play a role in the successful removal of an intron from mRNA?

<p>Shine-Dalgarno sequence.</p> Signup and view all the answers

The adapter molecule that serves as a link between the genetic code in mRNA and the amino acids that make up a protein is _____ RNA.

<p>Transfer.</p> Signup and view all the answers

Which of the following is involved in RNA interference?

<p>miRNA.</p> Signup and view all the answers

In the experiment showing the noncolinearity of eukaryotic genes, was the DNA or RNA molecule longer?

<p>DNA.</p> Signup and view all the answers

Removal of introns from a pre-mRNA molecule in eukaryotes is termed RNA ____.

<p>Splicing.</p> Signup and view all the answers

What feature is most critical to tRNA function?

<p>Secondary structure.</p> Signup and view all the answers

What is the likely function of a long noncoding RNA that has several mRNA binding sites?

<p>Prevent splicing.</p> Signup and view all the answers

Which of the following types of genes would typically contain only nucleotide sequences designed for amino acid sequence of a protein?

<p>Neither bacterial nor eukaryotic genes.</p> Signup and view all the answers

Which of the following is/are not found in mature mRNA molecules in eukaryotes?

<p>Introns.</p> Signup and view all the answers

True or false? Bacterial and eukaryotic ribosomes each consist of a large subunit and small subunit.

<p>False</p> Signup and view all the answers

CRISPR RNAs in bacteria function like what system in the human body?

<p>Immune system.</p> Signup and view all the answers

Based on the experiment with hybridization, the gene must contain _____ exons and _____ introns.

<p>5; 4.</p> Signup and view all the answers

Which mechanism produces, from a single gene, multiple mRNAs of different lengths encoding different polypeptides? Choose all that apply.

<p>Both alternative splicing and RNA editing</p> Signup and view all the answers

True or false? When a 20S ribosomal subunit combines with a 30S subunit, the resulting complex will be 50S.

<p>False</p> Signup and view all the answers

How are miRNAs and siRNAs similar?

<p>Both interact with and use Dicer and RISC.</p> Signup and view all the answers

Which of the following facts about introns and exons are not true?

<p>Introns are very common in all organisms, both bacterial and eukaryotic genes.</p> Signup and view all the answers

The structure below is an intermediate in which process? (Choose: translation, polyadenylation, RNA splicing, transcription, replication)

<p>RNA splicing.</p> Signup and view all the answers

What is the correct sequence of events leading to successful RNA splicing?

<p>III, I, VI.</p> Signup and view all the answers

Why might RNA interference be critical in embryonic development?

<p>RNAi keeps this spatial and temporal expression in check.</p> Signup and view all the answers

Introns of which type of RNA are removed by spliceosomes?

<p>Nuclear pre-mRNA.</p> Signup and view all the answers

What mechanism can explain a geneticist identifying an mRNA molecule with the 5′ end from a gene on chromosome 3 and the 3′ end from a gene on chromosome 6?

<p>Trans-splicing.</p> Signup and view all the answers

What would likely happen to the function of tRNA if the sequence of the 3' end was mutated?

<p>The tRNA would not be able to bind any amino acid.</p> Signup and view all the answers

How is siRNA different than miRNA?

<p>siRNA molecules inhibit transcription.</p> Signup and view all the answers

The sequences on a eukaryotic gene that are represented in mature mRNAs are called ____.

<p>Exons.</p> Signup and view all the answers

What is the most likely effect of the mutation changing the branch point A within an intron to a U?

<p>Production of a longer than normal mRNA and an abnormal protein product.</p> Signup and view all the answers

Which rRNA component is likely to be part of a 40S ribosomal subunit?

<p>18S rRNA.</p> Signup and view all the answers

If a gene were arranged like the figure below, how many different mRNAs, with at least two exons, are possible through alternative splicing?

<ol start="4"> <li></li> </ol> Signup and view all the answers

Which of the following statements is true about gene structure?

<p>The DNA can be much longer than that of mRNA originated from the gene.</p> Signup and view all the answers

All of the following ribosomal RNA components are produced from cleavage of the 30S rRNA precursor, except ____.

<p>snoRNAs.</p> Signup and view all the answers

The diagram below shows a DNA molecule hybridized with an RNA molecule. The loop in the DNA molecule indicates the presence of a(n) ____.

<p>Intron.</p> Signup and view all the answers

How is the following statement incorrect? 'A gene is a sequence of nucleotides that encode amino acids in a protein.'

<p>It does not account for introns, 5' and 3' ends of mRNAs, and sequences that encode rRNAs and tRNAs.</p> Signup and view all the answers

Which mechanism allows rare bases to be incorporated into tRNA molecules?

<p>Enzyme-mediated chemical modifications of normal RNA bases.</p> Signup and view all the answers

You are running a transcription reaction in your lab. You stop the reaction after a few minutes and find that you have three predominant DNA and RNA molecules in your test tube. All have different lengths. Which molecule is likely the pre-mRNA?

<p>The third molecule (40 nucleotides).</p> Signup and view all the answers

Which letter in the diagram below indicates the site at which amino acids attach to this molecule?

<p>A.</p> Signup and view all the answers

Are all eukaryotic genes colinear?

<p>False</p> Signup and view all the answers

Which is the most precise definition of a gene?

<p>The entire DNA sequence that is required to transcribe and encode a single RNA molecule.</p> Signup and view all the answers

What is a codon?

<p>A set of three mRNA nucleotides that codes for a specific amino acid.</p> Signup and view all the answers

What is the Shine-Dalgarno sequence?

<p>The ribosome binding site in bacterial RNA.</p> Signup and view all the answers

Which is not a characteristic of the 5' cap?

<p>The 5' cap is a tag for mRNA degradation.</p> Signup and view all the answers

What is necessary for the addition of the poly(A) tail?

<p>The consensus sequence, AAUAAA.</p> Signup and view all the answers

Which mRNA sequence does not play a role in intron splicing?

<p>The Shine-Dalgarno sequence.</p> Signup and view all the answers

Which is not found in a spliceosome that is actively splicing?

<p>DNA.</p> Signup and view all the answers

Which is not a variation of splicing?

<p>Progressive splicing.</p> Signup and view all the answers

Alternative splicing produces?

<p>mRNAs of different lengths from the same pre‑mRNA.</p> Signup and view all the answers

Which is not a type of pre‑mRNA processing in eukaryotes?

<p>3' mRNA degradation.</p> Signup and view all the answers

What is the outcome of RNA editing?

<p>The protein translated from the edited mRNA has a sequence different from its gene.</p> Signup and view all the answers

What is the role of the acceptor arm of the tRNA molecule?

<p>Binding a specific amino acid.</p> Signup and view all the answers

Which statement is not correct about how siRNAs and miRNAs function?

<p>They can integrate into DNA sequences of specific genes.</p> Signup and view all the answers

What are CRISPR RNAs?

<p>RNAs found in prokaryotes that function in defense against foreign DNA.</p> Signup and view all the answers

Study Notes

Gene Structure and RNA Processing

  • Unknown gene contains 6 exons and 5 introns based on hybridization results.
  • Eukaryotic genes generally have non-coding regions (introns) removed during mRNA maturation.
  • mRNA has a 5' cap added for stability and ribosome binding, a modification not present in tRNA or rRNA.

RNA Interference and Splicing

  • RNA interference (RNAi) is a gene-silencing mechanism initiated by double-stranded RNA (dsRNA).
  • Steps include: introduction of dsRNA, cleavage into short dsRNA, binding with RISC, degradation of the sense strand, pairing of antisense strand with target mRNA, and silencing of gene expression.
  • The spliceosome is responsible for removing introns and joining exons to generate mature mRNA.

mRNA Modifications

  • Polyadenylation at the 3' end stabilizes mRNA, prevents degradation, and aids in ribosome binding.
  • Deleting the AAUAAA consensus sequence prevents cleavage at the polyadenylation site; deletion of the poly(A) tail affects mRNA cytoplasmic transport; removing the 5' cap leads to intron retention.

Alternative Splicing and Gene Regulation

  • Alternative splicing allows a single gene to produce multiple mRNA variants, leading to different protein products.
  • RNAs associated with gene expression regulation include miRNA, which blocks translation of specific mRNAs.

Properties of tRNA and Ribosomes

  • tRNA's critical features include its secondary structure and specific binding at the 3' end for amino acids.
  • Ribosomes consist of large and small subunits in both bacteria and eukaryotes, with specific rRNA components.

Experimental Observations in Gene Studies

  • The non-colinearity of eukaryotic genes is demonstrated by comparing the lengths of DNA and corresponding mRNA.
  • DNA is longer than mRNA due to the presence of introns in the former.
  • Trans-splicing can occur, combining exons from different genes, illustrating the complexity of RNA maturation.

Functions and Mechanisms

  • CRISPR RNAs in bacteria provide a form of defense similar to an immune system in higher organisms.
  • Modification of tRNA bases ensures functionality during protein synthesis.
  • siRNA may inhibit transcription while miRNA primarily acts on mRNA translation.

Molecular Mechanisms and Effects of Mutations

  • Mutations affecting branch points in introns can lead to longer mRNA and abnormal protein products due to ineffective splicing.
  • RNA editing can alter the protein product translated from the mRNA, sometimes resulting in a sequence distinct from that encoded by the gene.

Summary of mRNA and Genetic Concepts

  • Exons are retained in mature mRNA, while introns are removed through splicing.
  • Codons are sequences of three nucleotides in mRNA that correspond to specific amino acids in proteins.
  • The Shine-Dalgarno sequence is crucial for ribosome binding in bacterial translation.

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Test your understanding of DNA-RNA hybridization experiments and gene structure with these flashcards from Chapter 14. This quiz will help you explore critical concepts including exons, introns, and their roles in genetic expression. Perfect for preparing for exams or enhancing your knowledge of molecular biology.

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