Genetic Change G.Burgess 2012

Chromosomal Dissorders Nondisjunction Deletion Duplication Translocation Inversion Genetic Dissorders Point mutation Insertion Deletion Splice site mutation Nonsense mutation Silent mutation Missense mutation

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

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.

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

Translocation a fragment of a chromosome is moved ("trans-located") 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

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

Insertion/ deletion Addition or subtraction of nucleotide base(s) from a chromosome Example –Huntington`s Disease.

Information Links for Genetic Dissorders e.asp, UNIQUE, understanding rare chromosomal disordershttp:// e.asp Chromosomal disorder outreach.