Mutations Notes

Mutations A change in the DNA of the hereditary material of life

Mutations Can be: Good Bad Neutral Leads to adaptation Leads to cancer Typically go unnoticed

Who’s affected? If a mutation is in a somatic, or body cell, it will only change that person. Also, skin cancer

Who’s affected? If the mutation is in a gamete, or sex cell, the offspring will have that change also. Also, family cancer lines Albinism – mutation within the recessive genes that is passed down

Types of Mutations: Chromosomal: Deletions “ - ” Additions “ + ” Inversions “flip flop” Translocations “swap” Nondisjunction “don’t split”

Chromosomal: Deletion Mutations When a chromosome breaks and some of the genetic material is lost

Williams Syndrome Williams syndrome is caused by a genetic abnormality, specifically a deletion of about 27 genes from the long arm of one of the two chromosome 7s.Typically this occurs as a random event during the formation of the egg or sperm from which a person develops. In a small number of cases it is inherited from an affected parent in an autosomal dominant manner.

Chromosomal: Insertion Mutations When a fragment of a chromosome is inserted into another chromosome

Huntington's disease and the fragile X syndrome are examples of insertion mutation wherein trinucleotide repeats are inserted into the DNA sequence leading to these diseases.

Chromosomal: Inversion When a broken chromosome segment is reversed and inserted back into the chromosome

Hemophilia A

Chromosomal: Translocations When a fragment of one chromosome joins to a non-homologous chromosome

Disease Caused by Translocation Cancer: Several forms of cancer are caused by acquired translocations (as opposed to those present from conception); this has been described mainly in leukemia Down syndrome is caused in a minority (5% or less) of cases by a Robertsonian translocation of the chromosome 21 long arm onto the long arm of chromosome 14. XX male syndrome: caused by a translocation of the SRY gene from the Y to the X chromosome Infertility: One of the would-be parents carries a balanced translocation, where the parent is asymptomatic but conceived fetuses are not viable.

Chromosomal: Nondisjunction Failure of chromosome pairs to separate properly during meiosis - (in anaphase-1 or 2) It can result in a trisomy or monosomy

Nondisjunction disorders