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Genetics - Coggle Diagram

- - - - Nucleotides are joined together by covalent bonds between the deoxyribose sugar of one nucleotide and the phosphate group of the next.
        This arrangement make an alternating chain of deoxyribose sugar and phosphate groups in the DNA polymer - aka
        the sugar-phosphate backbone.
      - A and G bases, which have two rings, are called purines
      - C and T bases, which have just one ring, are called pyrimidines.
    - - DNA molecules have anti-parallel structure -
        strands run along each other but in opp directions
      - two strands are held of double helix
        held together by hydrogen bonds between
        nitrogenous bases on opp strands
      - Each pair of bases lies flat, forming a "rung" on the ladder of the DNA molecule.
      - The A-T and G-C associations are known as complementary base pairs.
- - - - Adult onset disorders
        
        Epilepsy
        
        Glaucoma
        
        Schizophrenia
      - Environmental influences eg. teratogens
        
        Chemicals and drugs – e.g. alcohol during pregnancy -> fetal alcohol syndrome
        
        Cigarette smoking during pregnancy -> low birth weight, SIDS
        
        Irradiation/radioisotopes during 1st trimester -> mental retardation, microcephaly
      - Congenital malformations
        
        Cleft lip/palate
        
        Congenital heart defects
        
        Neural tube defects
  - - - Nondisjunction
        
        Chromosome fail to separate properly
        cell with 1+ extra or missing chromosomes -
        aneuploid
      - Translocation
        
        location of chromosome segment is moved
        
        crossing-over between 2
        nonhomologous chromosomes
        
        eg. Down syndrome results from a portion of chromosome 21 becoming part of another chromosome, so individuals have 3 copies of that part of chromosome 21
  - - - Dominant X-linked
        
        conditions can be passed from either affected parent to their children.
        
        If the father has the affected copy of the gene he will only pass the condition to his daughter(s) and not his son(s), as fathers only pass X chromosomes to their daughters and Y chromosomes to their sons.
      - Recessive X-linked
        
        conditions are always passed through the maternal line with the condition appearing in males and being carried in females, but not usually expressed.
  - - - Common polygenic disorders
        (genetic disorder caused by the combined
        action of more than one gene) -
        
        Alzheimers
        
        Diabetes
        
        Cancer
        
        Eczema
- - - - Frameshift mutations
        
        Because the genetic code is read in codons (3 bases), inserting or deleting bases may change the way the nucleotides are interpreted as codons beyond the point of the mutation.
        These types of mutations are called frameshift mutations, and they may change the amino acid sequence
    - - Nonsense mutations
        result in a stop codon where
        an amino acid should be, causing
        translation to stop prematurely
      - Missense mutations
        change the amino acid specified
        by a codon.
      - Silent mutations
        do not affect the sequence of
        amino acids during translation
  - - - any remaining mis-paired bases can be detected
        & replaced in a process called mismatch repair.
    - - If DNA gets damaged, it can be repaired by
        various mechanisms
    - - most DNA polymerases "check their work,"
        fixing the majority of mis-paired bases (proofreading).
- - - - RNA is generally single-stranded instead of double-stranded.
      - RNA contains uracil in place of thymine
      - RNA uses the sugar ribose instead of deoxyribose.
      - These 3 differences help enzymes in the cell to distinguish
        DNA from RNA
  - - - Non-coding RNA that forms the structural component of ribosomes
    - - Non-coding RNA that carries amino acids to the ribosome during translation to help build an amino acid chain
    - - Coding RNA that carries information from DNA in the nucleus to ribosomes in the cytoplasm
    - - Non-coding RNA involved in regulation of gene expression post-transcription