Genetically Inherited Diseases Flashcards
Etiology of Down Syndrome
Presence of all or a portion of a third chromosome 21
Critical region of Down Syndrome
21q21.22
Is the ‘p’ or ‘q’ arm longer
q is longer
What is a homologous pair
A paternal chromosome and a maternal chromosome that code for the same gene but may have different alleles
Does the incidence increase or decrease with maternal age
Increases
Why might incidence of certain conditions increase with age
Non-dysjunction occurrences increase during cell division
Why is trisomy 21 more common that trisomy 13
Post natal survival is higher in trisomy 21 as chromosome 21 is smaller, therefore less genes are affected than chromosome 13
Cause of trisomy 21
Non-dysjunction or Robertsonian translocation
What is non-dysjunction
Disomic gametes due to….
What is Robertsonian translocation
Numerical chromosome abnormalities
Gain or loss of complete chromosome
Serious, lethal consequences
Autosomal often not compatible with life
Fewer serious effects from sex chromosome anomalies
What is microdeletion mutation
Small bits of chromosome are deleted, minimum 24 genes
Example of microdeletion condition and where it occurs
DiGeorge syndrome, 22q11.2
Mutation definition
Change in the sequence of DNA with clinical consequence
