RNA and Protein Synthesis Overview

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Questions and Answers

What is the function of ribosomes?

Ribosomes are the organelles that assemble amino acids into proteins.

Which of the following is NOT a function of RNA?

  • Aid in protein synthesis
  • Store genetic information (correct)
  • Carry genetic information from DNA to ribosomes
  • Provide structural support for cells

Transcription occurs in the cytoplasm of eukaryotic cells.

False (B)

What is the name of the enzyme that carries out transcription?

<p>RNA polymerase (B)</p> Signup and view all the answers

Which of the following is NOT a step in gene expression?

<p>Replication (B)</p> Signup and view all the answers

What is the function of a promoter in DNA?

<p>A promoter is a specific DNA sequence that marks the start of a gene and provides a binding site for RNA polymerase.</p> Signup and view all the answers

What is the name of the process by which introns are removed from a newly transcribed RNA molecule?

<p>Splicing (A)</p> Signup and view all the answers

What is the function of a poly-A tail added to a mature mRNA?

<p>A poly-A tail helps protect the mRNA from degradation, promotes its export from the nucleus, and aids in translation efficiency.</p> Signup and view all the answers

Which type of RNA carries the genetic code from DNA to ribosomes for protein synthesis?

<p>mRNA (A)</p> Signup and view all the answers

A set of three consecutive nucleotides in an mRNA molecule that codes for a specific amino acid is called a ______.

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

Match the following types of RNA with their primary function:

<p>mRNA = Carries amino acids to ribosomes tRNA = Serves as a template for protein synthesis rRNA = Provides structural support for ribosomes snRNA = Involved in splicing pre-mRNA</p> Signup and view all the answers

Flashcards

Ricin

A highly toxic protein from the castor oil plant, lethal in small doses with no antidote.

Gene

A segment of DNA that encodes instructions for building RNA or protein products.

Transcription

The process of synthesizing RNA from a DNA template.

mRNA

Messenger RNA that carries genetic information from DNA to ribosomes for protein synthesis.

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Translation

The process where ribosomes decode the information in mRNA to produce proteins.

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Ribosome

A cellular structure where protein synthesis occurs, made up of rRNA and proteins.

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tRNA

Transfer RNA that carries amino acids to ribosomes during translation, matching anticodons to codons.

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Codon

A sequence of three nucleotides in mRNA that specifies a single amino acid or stop signal during translation.

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Genetic code

The set of rules by which information encoded in mRNA is translated into proteins, consisting of 64 codons.

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Start codon

The specific codon (AUG) that signals the start of translation, also coding for methionine.

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Stop codons

Codons that signal the termination of translation, indicating where the protein synthesis ends.

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Ribosomal RNA (rRNA)

RNA that forms the core of the ribosome's structure and catalyzes protein synthesis.

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Introns

Non-coding sequences within a gene that are removed during RNA processing.

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Exons

Coding sequences that are retained in mRNA after splicing and contribute to the final protein product.

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Alternative splicing

The process by which different combinations of exons are joined together to produce different proteins from the same gene.

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Poly-A tail

A sequence of adenine nucleotides added to the 3' end of mRNA for stability and export from the nucleus.

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Promoter

A DNA sequence where RNA polymerase binds to start transcription of a gene.

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RNA polymerase

The enzyme that synthesizes RNA by linking RNA nucleotides together based on a DNA template.

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Peptide bond

A bond formed between amino acids during protein synthesis, linking them into a polypeptide chain.

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Mutations

Permanent changes in a DNA sequence that can affect gene function or protein production.

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Base-pair substitution

A type of mutation where one nucleotide is replaced by another in the DNA sequence.

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Frameshift mutation

A mutation caused by a deletion or insertion that shifts the entire reading frame of codons.

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Sickle-cell anemia

A genetic disorder caused by a mutation in the beta globin gene, leading to abnormal hemoglobin structure.

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Hemoglobin

A protein in red blood cells that carries oxygen, composed of four polypeptides.

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Eukaryotes

Organisms whose cells have a nucleus and organelles, including RNA processing in the nucleus.

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Prokaryotes

Single-celled organisms without a nucleus, where transcription and translation happen simultaneously.

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Study Notes

Ribonucleic Acid (RNA) and Protein Synthesis

  • RNA is a crucial molecule in protein synthesis
  • It's similar to DNA but single-stranded
  • RNA nucleotides have ribose sugar, phosphate groups, and four bases (adenine, uracil, cytosine, guanine)
  • Three main types of RNA involved in protein synthesis: mRNA (messenger), tRNA (transfer), and rRNA (ribosomal)

Ribosome Inactivating Proteins (RIPs)

  • Ricin is a highly toxic naturally occurring protein
  • Kills by inactivating ribosomes, essential for protein synthesis, in cells
  • Effectively deters insects, birds, mammals etc. from eating castor oil plant seeds
  • Ricin production is a concern as a weapon; no antidote
  • Used in past terrorist attacks and plots
  • A ribosome-inactivating protein (RIP) occurs naturally in some bacteria, mushrooms, algae and other plants
  • Includes food crops like tomatoes, barley, spinach

Gene Expression

  • Genes carry instructions for building proteins
  • DNA holds genetic information
  • Information in a gene is converted to RNA (transcription)
  • Then converts information in mRNA into a protein (translation)
  • DNA is like an encyclopedia
  • RNA is like a disposable copy of a gene
  • Transcription converts DNA info into RNA, through RNA polymerase
  • Translation converts RNA into a polypeptide
  • Polypeptide folds into a protein
  • Proteins perform various life processes

Transcription (DNA to RNA)

  • RNA polymerase is the main enzyme
  • Requires a promoter sequence on DNA for binding
  • Non-coding DNA strand acts as a template to make RNA
  • RNA is assembled from RNA nucleotides
  • Base-pairing rules govern assembly

Translation (RNA to Protein)

  • Ribosomes (comprised of rRNA and proteins) assemble polypeptide chains
  • Takes place in cytoplasm
  • Genetic code (codon-amino acid pairings) dictates order of amino acids
  • tRNAs deliver amino acids to ribosomes
  • Ribosomes connect amino acids with peptide bonds
  • Translation ends when a stop codon is reached

Mutated Genes and Protein Products

  • Mutations can lead to changes in a gene's product
  • Base-pair substitutions
  • Deletion or insertion of base pairs cause frameshift mutations that alter the entire amino acid sequence
  • Examples: Sickle-cell anemia, beta-thalassemia
  • Mutations can result in a variety of diseases, including various cancers

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