Mutations
Changes in the genetic material.Any deviation from the normal
chromosomal complimentTwo types:
Spontaneous mutations-occur randomly; no cause can be determined
Induced mutations are caused by some traceable artificial factor: exposure to chemicals, alcohol, drugs, radiation
Mutations
Mutations that produce changes in a single gene are gene mutations.
Mutations that produce changes in a whole chromosome are chromosomal mutations.
Gene Mutations
Point mutation-change in one or just a few nucleotides. So named because it occurs at a single point.SubstitutionsDeletions Insertions
Gene Mutations
Frameshift mutation—shift the reading frame of the genetic codeCan alter a protein so much that it can’t
perform its job.
Chromosomal Mutations
Involve a change in the number or structure of the chromosome
Some change the location of some genes on the chromosome
Some may change the number of copies of some genes.
Deletion
The permanent loss of a segment of chromosome
Can be found anywhere on the chromosome
Can be caused by heat, radiation, viruses, chemicals, errors
Duplication
Doubles a segment of chromosomeCan be fatalCan be caused by uneven crossing over
during meiosis or replication error before meiosis
Causes of abnormalities
NondisjunctionThe failure of the chromosome pairs to
separate during Meiosis I or Meiosis IIResult will be a zygote with too many or too
few chromosomesTwo types: Primary and secondary
nondisjunction
Types of Genetics Tests
When trying to determine a genetic problem, we can use non-invasive tests such as
PedigreesKaryotypes
Pedigrees
A pedigree follows a specific trait through several generations
Resembling a type of map, the pedigree uses symbols to represent certain elements
Karyotypes
A photographic inventory of an individual’s chromosomes
Can show the individual’s gender and any abnormalities in chromosome number or structure
Amniocentesis Pros and Cons
Able to determine fetus’ gender and/or any abnormalities
Can’t be done before 16th week of pregnancy
Can cause infection to mother and/or fetus
Can cause premature delivery and birth
CVS Pros and Cons
Can determine fetus gender and any genetic abnormalities
Can be done after 10 weeksCan cause leakage of amniotic fluidCan cause premature labor and delivery
Recessive Disorders
Must be inherited from BOTH parentsAutosomal recessive disorders (non-sex
cells)Tay-SachsPKUCystic fibrosis
Recessive Disorders
Tay-Sachs—lipid accumulation in the brain; mental deficiency; blindness, death in early childhood
PKU-phenylketonuria—accumulation of phenylalanine in tissues; lack of normal skin pigment; mental retardation
Cystic fibrosis—excess mucus in lungs, digestive tract, liver; increased susceptibility to infections; often die young
Dominant Disorders
Can get the disorder by inheriting only one dominant alleleHuntington’s diseaseAchondroplasia
Dominant Disorders
Huntington’s DiseaseMental deterioration and uncontrollable
movementsDoesn’t appear until middle age
AchondroplasiaOne form of dwarfism
Sex Linked Disorders
Is there a pattern of inheritance for genes located on the X or Y chromosome? YES especially on the X
Many times it is male children that inherit these disorders from their mothers because . . . They inherit their X from their mom’s
Many sex linked genes are on the X Colorblindness Hemophilia Duchenne Muscular Dystrophy
Sex Linked Disorders
ColorblindnessMost often found in males
1 in 10 malesFemales have to inherit from both parents
1 in 100 femalesMost common is red-green colorblindness
Sex Linked Disorders
HemophiliaTwo genes on the X chromosome control
blood clottingMany times it is male children that inherit
this from their mom’s X chromosome1 in 10,000 malesA bleeding disorder; can cause death in
severe cases
Sex Linked Disorders
Duchenne Muscular Dystrophy1 in 3000 malesProgressive weakening and loss of skeletal
muscleCaused by defective version of gene that
codes for a muscle protein
Genetic Disorders
TrisomyDowns Syndrome (extra chromosome 21)Edwards Syndrome (extra chromosome 18)Patau Syndrome(extra chromosome 13)