Genetic Change

1
Genetic Change

• G.Burgess
• 2012

2
Chromosomal Dissorders
Genetic Dissorders

• Nondisjunction
• Deletion
• Duplication
• Translocation
• Inversion

• Point mutation
• Insertion
• Deletion
• Splice site mutation
• Nonsense mutation
• Silent mutation
• Missense mutation

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Non Disjunction

• Chromosomes do not separate during anaphase
  (non-disjunction)
• Both chromosomes go to one cell during anaphase
  causing one cell to have too many chromaomes and
  the other not having enough.
• Example
• Down Synrdom trisomy 21
• Klinefelters Syndrom XXY
• XYY males
• XXX females
• Turner Syndrom XO females

4
Deletion

• When a part of a chromosome is lost during cell
  division
• Example
• Cri du Chat occurs with a deletion of part of
  chromosome 5.

5
Duplication

• if a DNA fragment joins the homologous chromosome
  and that region is repeated
• Example
• Fragile X

6
Translocation

•  a fragment of a chromosome is moved ("trans-locat
  ed") from one chromosome to another
• joins a non-homologous chromosome.
• nothing has been gained or lost but it places
  genes in a new environment.
• Example
• Acute Myelogenous Leukemia

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Point Mutations

• Single base substitutions 
• may occur as a single nucleotide base is replaced
  by other base.
• Examples
• Cystic fibrosis
• Cancer
• Sickle cell anemia
• Tay sachs disease
• Colour blindness

8
Insertion/ deletion

• Addition or subtraction of nucleotide base(s)
  from a chromosome
• Example
• Huntingtons Disease.

9
Information Links for Genetic Dissorders

• http//www.rarechromo.org/html/home.asp, UNIQUE,
  understanding rare chromosomal disorders
• http//www.chromodisorder.org/CDO/, Chromosomal
  disorder outreach.