Gene Structure and Expression Quiz

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Questions and Answers

What distinguishes the transcription process in prokaryotes from eukaryotes?

  • Eukaryotes utilize RNA polymerase I, II, and III. (correct)
  • Eukaryotes have operons that group related genes.
  • Prokaryotes use ribosomes to initiate transcription.
  • Transcription occurs in the nucleus in prokaryotes.

Which correctly describes how transcription is initiated in eukaryotes?

  • Transcription begins automatically without any proteins.
  • Ribosomes directly bind to DNA to start transcription.
  • Promoter regions are not involved in transcription initiation.
  • Transcription factors bind to the promoter region. (correct)

Which statement accurately describes the function of RNA polymerases in eukaryotes?

  • They play different roles in transcribing various types of RNA. (correct)
  • They are exclusively responsible for synthesizing ribosomal RNA.
  • They can only synthesize RNA when bound to ribosomal proteins.
  • They can synthesize both DNA and RNA strands.

What must happen during transcription mechanisms before RNA is synthesized?

<p>The DNA strand must be unwound and a complementary RNA strand formed. (C)</p> Signup and view all the answers

How is gene organization typically structured in prokaryotes?

<p>Genes are organized into operons for related functions. (C)</p> Signup and view all the answers

What is the relationship between genes and enzymes as observed in Beadle and Tatum's experiments?

<p>Genes directly encode proteins that catalyze reactions. (C)</p> Signup and view all the answers

What evidence did Garrod provide regarding the link between genetics and metabolic disorders?

<p>Identified that certain metabolic disorders are inherited and linked to gene alterations. (B)</p> Signup and view all the answers

Which statement best explains the effect of X-rays in Beadle and Tatum's study on Neurospora crassa?

<p>X-rays induced mutagenesis, impacting specific genes encoding enzymes. (D)</p> Signup and view all the answers

What was the purpose of comparing wild type and auxotrophic mutants in Beadle and Tatum's research?

<p>To identify the steps in the arginine synthesis pathway and their gene associations. (A)</p> Signup and view all the answers

Which conclusion can be drawn from the argF and ArgE mutants' behavior in the arginine synthesis pathway?

<p>Each mutant has a unique defect in the enzyme synthesis path. (D)</p> Signup and view all the answers

What is the primary function of the promoter in a gene?

<p>To initiate transcription by providing a binding site for RNA polymerase (D)</p> Signup and view all the answers

How do prokaryotic and eukaryotic transcription processes differ regarding RNA polymerase binding?

<p>Eukaryotic RNA polymerase requires transcription factors to bind to DNA (B)</p> Signup and view all the answers

Which codon serves as the start codon for translation?

<p>AUG (C)</p> Signup and view all the answers

What is the role of RNA polymerase during transcription?

<p>To add RNA nucleotides sequentially according to the DNA template (A)</p> Signup and view all the answers

What defines the termination of transcription in a gene?

<p>The terminator signals the end of transcription (C)</p> Signup and view all the answers

How does the genetic code's universality affect coding for amino acids?

<p>The same codons specify the same amino acids across all organisms (C)</p> Signup and view all the answers

What does redundancy in the genetic code refer to?

<p>Some amino acids are specified by multiple different codons (A)</p> Signup and view all the answers

What is the direction of RNA synthesis during transcription?

<p>5’ to 3’ direction (C)</p> Signup and view all the answers

Which of the following is NOT a stop codon?

<p>AUG (D)</p> Signup and view all the answers

Flashcards

Codon

A sequence of three nucleotides that specifies a particular amino acid during protein synthesis.

Translation

The process of converting the information in a messenger RNA molecule into a sequence of amino acids in a polypeptide chain.

Reading Frame

The way in which the sequence of nucleotides is read in groups of three.

Start Codon

The specific codon (AUG) that signals the start of translation, indicating where protein synthesis should begin.

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Stop Codon

A codon (UAA, UAG, or UGA) that signals the termination of translation, stopping protein synthesis.

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Transcription

Process of creating an RNA copy of a DNA sequence.

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RNA Polymerase

Enzyme that synthesizes RNA from a DNA template.

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Promoter

Region of DNA that initiates transcription.

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Transcription Unit

Part of a gene that contains the code to make an RNA molecule.

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Terminator

Region of DNA marking the end of a gene.

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One gene-one polypeptide hypothesis

Different genes encode different polypeptide chains, which can combine to create functional proteins, not just enzymes.

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Genetic code (triplet code)

A sequence of three nucleotides (a triplet) in DNA or RNA that specifies a particular amino acid.

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What is the role of genes?

Genes hold the instructions on how to build proteins through the processes of transcription and translation.

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How do we know genes code for proteins?

Experiments by Garrod and Beadle and Tatum established the link between genes, enzymes, and metabolic disorders.

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What is alkaptonuria?

A metabolic disorder where the body can't properly break down a chemical, leading to it turning black in the air.

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What is an auxotroph?

A nutritional mutant that requires specific nutrients to grow.

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What is the Beadle and Tatum experiment?

An experiment that used X-rays to create nutritional mutants in bread mold, demonstrating the link between genes and enzymes.

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Study Notes

Gene Structure and Expression

  • Genes provide instructions for building proteins through transcription and translation.
  • Proteins carry out many cellular functions.

How Genes Encode Proteins

  • Garrod (1896) studied alkaptonuria, a metabolic disorder, linking it to a gene alteration.

  • Beadle and Tatum (1940s) investigated orange bread mold (Neurospora crassa) to further explore the relationship between genes and enzymes.

  • Their hypothesis suggested a specific gene for each enzyme involved in a metabolic pathway.

  • Garrod's work demonstrated that alterations in genes result in metabolic disorders, and that these disorders are often inherited.

  • Beadle and Tatum's experiments supported that a single gene, codes for a single enzyme.

Beadle and Tatum Experiment

  • The experiment utilized orange bread mold (Neurospora crassa).
  • Each step in a metabolic pathway (e.g., arginine synthesis) is regulated by a gene that encodes the specific enzyme.

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