Transcription and Translation - A2 Biology (Unit 5)

A brief overview of Transcription, Translation, Splicing, siRNA, Mutations, Transcription Factors and Oestrogen (as a Transcription Factor).

Note - When using key terms, it is better to write a list of key terms that you remember from the previous slide and then match them to the 'key terms' slide.

  • Created by: NewGirl.
  • Created on: 28-03-13 09:57

Main Topics - Transcription and Translation

  • Transcription
  • Splicing
  • Transcription
  • Protein Synthesis
  • siRNA
  • Translation Factors
  • Oestrogen
  • Mutations
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Transcription - Process

Transcription is the process where the information in DNA is transferred to the Ribosomes in the Cytoplasm in the form of mRNA.

1-   The hydrogen bonds between Nucleotide bases break, and the double helix of the DNA begins to unwind.

2- RNA Polymerase recognises a 'Start' code on the strand of DNA and attaches itself to the DNA at this point.

3- RNA Polymerase moves along the strand of DNA and catalyses the production of mRNA molecules, where free Nucleotide bases attach to the complimentary bases on the DNA strand. HOWEVER - Instead of Thymine, Uracil forms a bond with Adenine.

5- Splicing occurs to remove Introns from the Pre-mRNA to produce Mature mRNA.

4- After Transcription is completed, the mRNA moves out of the Nuclear pores and into the Cytoplasm for Translation. The Double-helix of the DNA is reformed.

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Key Terms - Transcription

  • DNA
  • Double helix
  • Hydrogen bonds (H+ Bonds)
  • Unwinds
  • Nucleotide bases
  • RNA Polymerase
  • Start Code
  • Complimentary
  • Splicing
  • Introns
  • Exons
  • Pre-mRNA
  • Mature mRNA (mRNA)
  • Single-Stranded (mRNA)
  • Double-Stranded (DNA)
  • Nucleus
  • Nuclear Pores
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Translation: Process

Translation is the process where mRNA is used to combine with tRNA in order to produce a Polypeptide chain of Amino Acids.

1- mRNA from Transcription attaches to a Ribosome.

2- tRNA molecules carry Amino Acids to the Ribosome, where they Amino Acids attach to the Amino Acid binding site on the tRNA.

3- The tRNA Molecule has a complimentary anti-codon to the codon on the start of the mRNA strand and binds with the mRNA.

4- A second tRNA molecule binds to the next codon on the mRNA, there are now 2 Amino Acids present and so, a peptide bond forms between them.

5- Process is repeated until a 'Stop code' is reached, and the polypeptide chains moves away from the Ribosome.

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Key Terms- Translation

  • mRNA
  • tRNA
  • Cytoplasm
  • Ribosome
  • Amino Acids
  • Codon
  • Anti-Codon
  • Complimentary
  • Start Code
  • Stop Code
  • Peptide Bond
  • Clover Shape
  • Amino Acid Binding Site
  • Moves away
  • Polypeptide Chain
  • Protein Synthesis
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Transcription Factors

Transcription Factors control the Transciption of Target Genes

  • Transcription Factors move from the Cytoplasm to the Nucleus
  • They bind to specific DNA sites near the start of their Target Genes
  • They control expression by controlling the rate of transcription.
  • Activators = increase the rate of transcription. E.G they help RNA polymerase bind to the start of the Target Gene.
  • Repressors = Decrease the rate of transcription = E.G Bind to the start of the target gene and preventing RNA Polymerase from binding and so stopping transcription in itself.

Oestrogen is an example of a Transcription Factor.

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Key Terms - Transcription Factors

  • Control
  • target genes
  • bind
  • near target gene
  • prevent transcription
  • RNA Polymerase
  • Activators
  • Repressors
  • Cytoplasm
  • Nucleus
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Oestrogen - Transcription Factor

  • Oestrogen also affects Translation.

1- Binds to Transcription factor called 'Oestrogen-Receptor' = forming an Oestrogen-Oestrogen receptor complex.

2- The Complex moves into the nucleus and binds to a specific DNA site near the target Gene.

3- Oestrogen can then act as an Activator or a Repressor.

4- Level of Oestrogen affects the rate of transcription.

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Key Terms - Oestrogen

  • Transcription Factor
  • Transcription
  • Translation
  • Binding
  • Near Target Gene
  • Oestrogen
  • Oestrogen-Receptor
  • Oestrogen-Oestrogen Receptor Complex
  • Activator
  • Repressor
  • Nucleus
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Regulation - siRNA

siRNA is Small Interfereing RNA which can interfere with the expression of certain genes.

1- siRNA is short, double-stranded RNA and can interfere with gene expression.

2- Their bases are complimentary to those near a target Gene.

3-siRNA can interfere with both Transcription and Translation.

4- It does so through RNA interference, where:

  • siRNA binds to the target mRNA in the cytoplams.
  • The proteins attached to the siRNA cut up the mRNA and it can no longer be translated.
  • Prevents expression of the specific gene as its protein can no longer be made during translation.
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Key Terms - siRNA

  • siRNA
  • gene expression
  • short
  • double stranded
  • complimentary bases
  • binds
  • near target gene
  • RNA interference
  • cuts up
  • no longer useful
  • transcription
  • protein
  • inhibited
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Any change to the base sequence of DNA is called a mutation. They can be caused by Errors, Mutagenic agents. Errors include Substitution or Deletion.

  • Not all mutations affect the order of amino acids.
  • A substitution can result in the production of a different amino acid due to the degenerate nature of DNA where many amino acids can be coded for by more than one triplet code.
  • Deletions, however, will always results in a differerent Amino Acid, due to the frameshift that would occur when a base is removed.
  • Mutagenic agents occur spontaneously - however, some things may increase the rate of mutations.
  • Such as: Ultraviolet radiation, Ionising radiation, Chemicals, some viruses.
  • They do this by: Acting as a base, Altering Bases and Changing the structure of DNA.
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Key Terms - Mutations

  • Change
  • base sequence
  • mutation
  • errors
  • substitution
  • deletion
  • amino acid
  • protein
  • triplet code
  • Frameshift
  • mutagenic agents
  • radiation
  • chemicals
  • viruses
  • acting as a base
  • altering bases
  • changing DNA structure.
  • Degenerate Code
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Page 2: Generally numbers go in the order 1,2,3,4 and then 5...

Jokes aside, great revision cards!

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