Translation + Transcription

• Describe how the production of messenger RNA (mRNA) in a eukaryote cell is different from the production of mRNA in a prokaryote cell. 

  Introns are not contained within Prokaryotic DNA

  Splicing does not occur as splicing is the removal of introns.
• Suggest how PNA affected the transcription of the section of DNA. 

  PNA forms bonds with DNA bases. This prevents RNA nucleotides binding and reduces transcription
• Describe the role of ATP in the process of translation in protein synthesis. 

  ATP releases energy

  This energy forms phosphodiester bonds between DNA bases
• Define transcription

  A copy of gene is synthesised in the nucleus. This then carries the information needed to make a polypeptide into the cytoplasm, ready for translation.
• What is the 5 steps in transcription?

  DNA helicase hydrolysises the DNA strands

  RNA polymerase binds to the site of DNA, called the prometer region

  Free nucleotides within the nucleus pair with complimentry bases from the antisense strand. Forming phosphodiester bonds. Making pre-mRNA

  RNA polymerase continues down the chain, behind DNA helicase, reforming double helix.

  RNA polymerase reaches stop codon, detaches and pre-mRNA is released.
• What is splicing?


  The removal of introns, forming mature mRNA
• What are the 6 steps in translation?

  tRNA molecules carries the amino acids to the mRNA base sequences, mRNA attaches to ribosome.

  First tRNA anticodon binds to the complimentary codon to mRNA

  A second tRNA anticodon attaches to next mRNA codon

  A bond is formed between neighbouring amino acids, being held by tRNA. First tRNA unbinds leaving behind the amino acid

  Cycle then continues forming the primary chain of amino acids

  Complex reaches stop codon, protein detaches and moves elsewhere.
• What is a sense and antisense strand?

  Sense strand contains the same base sequence of mRNA

  Antisense strand contains the complimentary base sequence to mRNA, acting as a template.
• What does the prometer region do?

  Determines the beginning and end of transcription
• What bonds form between bases to make pre-mRNA

  Covalent + phosphodiester bonds
• How many bases can be used in RNA polymerase at a time?

  12
• How does the pre-mRNA leave the nucleus?

  Through the nuclear pores
• Why doesn't splicing occur in Prokayotic pre-mRNA

  Prokarytoic DNA does not contain introns

  No splicing can occur, meaning transcription in Prokaryotes makes mature mRNA
• How is the bond between tRNA and amino acids formed?

  Through ATP
• What bonds do anticodons and codons form together?

  Hydrogen bonds
• What is elongation?

  The formation of the primary chain of amino acids during translation
• What is a stop codon?


  Initiates the RNA polymerase to stop and detach.
• Describe how mRNA is formed by transcription in eukaryotic cells

  DNA helicase breaks bonds and releases nucleotides

  Nucleotides forms new complimentary pairs

  Only one strand acts as a template

  RNA polymerase reforms the phosphodiester bonds between bases

  Splicing removes any introns within the pre-mRNA and makes mature mRNA
• Describe how a polypeptide is formed by the translation of mRNA


  Ribosomal sub units attach to the strands of mRNA

  tRNA anti codons bind to complimentary mRNA codons

  tRNA brings the specific amino acids

  Amino acids join by peptide bonds

  Bonds are formed through ATP

  tRNA is released once amino acid joins

  Ribosome moves down the chain until the chain is formed
• Define a gene mutation and explain how a gene mutation can have:

  • No effect on an individual
  • A positive effect on an individual

  A gene mutation is a change in the base sequence

  Resulting in a new allele

  The DNA code is degenerate meaning a protein can be coded for by multiple base sequences

  Mutations may result in increased reproductive success