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Unit 8 - Coggle Diagram

- - - - Deletion
      - Addition
      - Substitution
    - - Section of a DNA molecule (a single gene)
      - DNA double helix unzips due to DNA helicase action. Hydrogen bonds between complementary bases break and the two polynucleotide strands separate.
      - One strand acts as a template while the other is a coding strand. Free RNA nucleotides form H-bonds with exposed bases according to complementary base pairing rules.
      - RNA polymerase forms phosphodiester bonds between RNA nucleotides to create a strand of RNA in a condensation reaction.
      - In eukaryotes, pre-mRNA detaches from the template strand. The two DNA strands join back together by complementary base pairing and wind back into a helix.
    - - Only takes place in eukaryotic cells
      - Removes introns from pre-mRNA to make mRNA
      - Alternative splicing is two different ways to splice the same pre-mRNA to make two similar but different proteins e.g. Antibody gene
    - - Ribosome attaches to the start and second codon on the mRNA.
      - Anticodon on the first tRNA binds to the complementary start codon on mRNA (H-bonds, complementary base pairing) bringing specific amino acids to ribosome.
      - Anticodon on second tRNA binds...etc.
      - ATP hydrolysis is required as a source of energy for the ribosome to form the peptide bond between amino acids.
      - The ribosome moves along the mRNA to cover codon 2 and 3.
      - The first tRNA is released. Anticodon on third tRNA binds ...etc.
  - - - Section of a chromosome detaches and re-attaches in the same position, but back to front
    - - One or more bases are repeated
      - Frame shift to the right
    - - A sequence of bases in a section of the chromosome detaches from the chromosome and re-attaches to a different chromosome in a different place
  - - - Deletion at end of gene 'affects every subsequent triplet' - so fewer triplets to affect
      - Deletion/addition of 3n bases only affects one codon (no 'frame shift'
- - - - Smaller and hydrophobic / non-polar
      - e.g. Oestrogen, Testosterone / e.g. ADH, Insulin
      - Passes through phospholipid bilayer by simple diffusion - receptors are in the cytoplasm
  - - - Remove acetyl groups from histones (Histone Deacetylase)
      - Add methyl groups to cytosine bases in DNA (Methyl Transferase)
      - DNA coils more tightly
      - Cause shape of promoter region to change, prevents transcription factors binding , this silences genes
      - Folded away genes prevent gene expression
    - - Remove methyl groups from DNA (Demethylase)
      - Add acetyl groups to histones (Histone Acetyltransferase)
      - Neutralises positive charges on histone proteins. The negative DNA can no longer wrap tightly and chromatin unwinds.
      - Unfolded genes allow gene expression, the genes are transcriptionally active
- - - - Divides repeatedly and differentiate into every cell type, therefore able to produce a full organism
      - e.g. Cells of the early embryo (up to 64 cell stage)
    - - Divide and differentiate into many different tissue types (not a full organism)
      - e.g. Cells of the later embryo
    - - Divide and differentiate to give many different cell types
      - e.g. Bone marrow stem cells produce all the different blood cells
    - - Divide and differentiate to give one cell type
      - e.g. Cardiomyocytes in the heart produce heart muscle cells
    - - A cell that has taken on a specific shape or structure in order to be able to perform a defined function within a tissue, organ or organism.
        It only expresses the genes it requires to perform this function.
        In many cases, they lose the ability to divide.
      - e.g. Motor neurone in adult human, heart muscle cell in adult human, gut epithelial cell in adult human
    - - Switch of some genes - because no longer able to divide to make some tissue types
        Switch on other genes - because now only divides to make some tissue types
  - - - Transplantation can replace any type of damaged tissue - prevent human suffering
      - Cells differentiate to all possible types of specialised cells
    - - Must be a tissue match - Ideally make a clone embryo of yourself to treat own disease
  - - - Consent easily given from donor
      - No embryo destruction
    - - Transplant can only replace few types of tissue damaged: more limited
      - Must be a tissue match
  - - - Self is donor - easy consent
      - No embryo destruction
      - Transplant can replace all types of tissue damage: beneficence
      - Self is donor - tissue match
    - - Current clinical trials indicate the science is not there yet