protein synthesis

• why do RNA nucleotides join together?

  a condensation reaction forming a phosphodiester bond
• what bases does RNA have?

  Adenine, Uracil, Guanine, Cytosine
• what is the role of RNA?

  take DNA information from the nucleus to the ribosomes where it can be used in protein synthesis
• What is the role of mRNA?

  carrying information from the DNA in the nucleus out to the ribosomes.
• what does DNA stand for?

  Deoxyribonucleic acid
• what does RNA stand for?

  Ribonucleic acid
• what are DNA base pairs held together by?

  hydrogen bonds
• what is the pre-mRNA stand?

  a copy of the DNA strand that is not being transcribed.
• what is the 1st step of transcription?

  RNA polymerase breaks hydrogen bonds between DNA bases, breaking the 2 strands apart and exposing the bases on each strand
• what is the 2nd step of transcription?

  RNA polymerase adds RNA nucleotides to complementary bases on one strand.
• What role does RNA polymerase have in transcription?

  Adds RNA nucleotides to complementary bases on one strand of DNA, known as the template strand.

  Attaches two strands of the DNA helix together.
• what is pre-mRNA complementary to?

  the DNA strand being transcribed
• what is pre-mRNA a copy of?

  the non-template DNA strand, with uracil replacing thymine
• Describe the processes involved in transcription.

  1. RNA polymerase breaks the hydrogen bonds between DNA bases, breaking the two strands apart and exposing the bases on each strand.
  2. RNA polymerase adds RNA nucleotides to complementary bases on one strand of DNA, known as the template strand.
  3. After the nucleotides are added by RNA polymerase, the DNA helix behind is reattached.
  4. RNA polymerase continues to move along the DNA strand until the pre-mRNA strand is complete.
  5. The pre-mRNA strand and RNA polymerase detach, leaving behind our original DNA helix and a complete strand of pre-mRNA.
• define gene

  a base sequence of DNA that codes for the amino acid sequence of a polypeptide and a functional RNA
• what is a non-coding sequence in a gene called?

  an intron
• what is a coding sequence in a gene called?

  an exon
• what is splicing?

  introns are removed to form mRNA and the remaining exons are attached together
• in mRNA, how many triplets code for an amino acid?

  1
• what does degenerate mean?

  multiple different codons can code for the same amino acid.
• what does non-overlapping mean?

  there is no overlap between codons when they are read: each part of the triplet is only read once.
• what does universal mean?

  all living organisms use the same genetic code; each triplet codes for the same thing in any organism.
• What is an anticodon?

   A set of 3 bases that are complementary to a codon on mRNA.
• what is a codon?

   set of 3 bases on a single mRNA strand. Each codon codes for an amino acid.
• What type of bond does this reaction form between the amino acids?

  peptide bond
• what happens in the 1st step of translation?

  a ribosome binds to the mRNA strand

  Then a molecule with a complementary anticodon binds to a codon on the mRNA strand, bringing an amino acid with it.This then repeats a second time with a second molecule.
• how does a ribosome join 2 amino acids together?

  using a condensation reaction, which forms a peptide bond between the amino acids
• what happens in the condensation reaction between 2 amino acids?

  The condensation reaction is catalysed by an enzyme

  It also requires ATP
• what are base pairs in tRNA held together by?

  hydrogen bonds (only in tRNA not mRNA)
• what is the start codon called?

  AUG - methionine
• Describe the process of translation?

  1. a ribosome binds to the mRNA strand.
  2. a tRNA molecule with a complementary anticodon binds to a codon on the mRNA strand, bringing an amino acid with it.This is followed by a second tRNA molecule, complementary to the next codon on the mRNA strand, binding to this codon.
  3. Each tRNA molecule carries an amino acid.The ribosome joins the amino acids together using a condensation reaction, which forms a peptide bond between amino acids. This is repeated until a polypeptide chain of amino acids is formed.
• what do genes code for?

  tRNA, mRNA, rRNA
• What type of gene is a functional RNA?

  tRNA and rRNA
• Which two types of molecules combine to form ribosomes?

  rRNA and proteins