Unit 1.3 - Control of DNA Expression

• What is gene expression?

  Gene expression is the activation of certain genes in a cell to produce particular proteins. Only a fraction of the genes in a cell are expressed.
• RNA is made up of what?

  A single strand of nucleotides.
• RNA nucleotides are made up of what?

  A phosphate group, a ribose sugar and a base.
• What are the four types of RNA bases?

  Adenine, uracil, guanine, cytosine.
• What are the 3 types of RNA?

  mRNA, tRNA, rRNA.
• What does mRNA (messenger) do?

  Carries a copy of the DNA code from the nucleus to the ribosomes.
• What does tRNA (transfer) do?

  Found in the cytoplasm where it binds to specific amino acids and transports them to the ribosome.
• What does rRNA (ribosomal) do?

  Forms a complex with protein molecules to make the ribosome.
• What are the two stages of gene expression?

  Transcription and translation.
• Where does transcription take place?

  In the nucleus.
• What enzyme breaks apart the hydrogen bonds and unwinds the double helix shape of DNA during transcription?

  RNA polymerase
• What does RNA do during transcription?

  Synthesizes a primary transcript of mRNA from using RNA nucleotides by complementary base pairing.
• What does Uracil pair with?

  Adenine.
• What is a triplet of bases called?

  Codon
• What does a codon code for?

  A specific amino acid.
• What are coding regions called?

  Exons
• What are non-coding regions called?

  Introns
• What does RNA splicing form?

  A mature mRNA transcript
• What happens to the introns in a primary transcript?

  They are removed.
• What happens to exons during RNA splicing?

  Exons are joined together to form the mature transcript.
• What are ribosomes composed of?

  Proteins and rRNA
• Why does tRNA fold?

  Complementary base pairing.
• What does tRNA do in translation?

  Carries amino acids to the ribosome
• What do tRNA molecules have on them?

  An anticodon and an amino acid attachment site.
• What is each anticodon complementary to?

  An mRNA codon.
• Where does translation begin?

  At the mRNA start codon
• Where does translation end?

  At a stop codon.
• What happens when the tRNA anticodon binds with a codon?

  It translates the genetic code into a sequence of amino acids.
• What bonds join amino acids together?

  Peptide bonds.
• What is a chain of amino acids called?

  A polypeptide chain
• What is alternative RNA splicing?

  Process of removing introns and joining exons in different combinations to produce multiple mRNA transcripts from a single gene.
• Why do polypeptide chains fold?

  To form the three dimensional shape of a protein.
• What is a phenotype?

  Observable characteristic of an individual
• What is an organism's phenotype determined by?

  The protein's produced as the result of gene expression and also environmental factors.