mutations & genetic disorders in 141 headings vocabulary important information
TRANSCRIPT
MutationsMutationsMutation: Any mistake or change in the DNA sequence
Point mutation: Change in
one nitrogen base in DNA
Ex: albinism
Changes in chromosome structure
1) INVERSION: the order of genes on a
chromosome is inverted
Chromosomal Mutation:Chromosomal Mutation:
2) TRANSLOCATION:
•the movement of a chromosome fragment to a nonhomologus chromosome
3. DELETION Loss of a few bases Loss of large regions
of a chromosome
4. DUPLICATION Duplication of a few
bases Duplication of large
regions of a chromosome
Crossing OverCrossing Over
Occurs when chromosomes exchange genes.
2 chromosomes overlap.
Some genes cross over and switch places
NONDISJUNCTIONNONDISJUNCTIONNondisjunction: chromosome pair fails
to separate properly during meiosis
Monosomy: gamete has 1 less
chromosome than it should
45 chromosomes is the result
Ex: Turner syndrome Missing a sex
chromosome
Trisomy: Gamete has 1
more chromosome than it should
Result is 47 chromosomes
Ex: Down’s SyndromeExtra #21
chromosome
Methods of DetectionMethods of Detection
Ultrasound: Sound waves are used to
generate an image of the unborn child.
Used to detect abnormalities of limbs, organs, etc.
Chorion villi sampling: •Take sample of the chorion
–(membrane surrounding fetus)
•Chemical tests and KaryotypingKaryotyping performed
Amniocentesis: • Fluid surrounding the fetus is drawn out by
needle
• Fetal cells are collected and grown in a lab.
• Chromosomes can be then Karyotyped
Autosomal DisordersDown’s Syndrome (Trisomy 21)
Patau’s Syndrome (Trisomy 13)
Edward’s Syndrome (Trisomy 18)
Down’s Syndrome (DS) Excess # 21 chromosome Prenatal testing can be done Result of chromosomal mutation 1 in 900 people born with this Likelihood of having a child with DS
increases with advancing maternal age Symptoms: mental retardation, upward
slant to eyes, small mouth, abnormal ear shape, decreased muscle tone
No cure
Patau’s Syndrome &Edward’s Syndrome
Cardiac abnormalitiesVery severe conditionsMost affected infants
die during first few weeks of life
Klinefelter’s Syndrome 47, XXY 1 in 1000 male live births Mild learning difficulties Taller than average with
long lower limbs Show mild enlargement of
breasts Infertile (absence of
sperm) Treat with testosterone
Turner’s Syndrome
45, XLow incidenceLook normalOvarian failureNormal intelligenceShort statureEstrogen therapy
Fragile X Syndrome
Most common inherited cause of mental retardation
1 in 2000 malesHigh forehead,
prominent jaw, autismGap in X chromosome
Cystic Fibrosis (CF) Recessive disorder Mutation stops production of
protein in lung cells, pancreas
Thick mucus, bacterial infections in lung
“sweat test” Most common in
Caucasians (1 in 3300) Chest percussions, diet
supplements Shortened life expectancy
Hemophilia
Sex-linkedFailure of blood to clotRare in females Injections with clotting factors to stop
bleeding episodes$350,000 a year in treatment
Sickle Cell Anemia Mutation in blood protein “sickle” shape to RBC Screening tests Most common in African-Americans
(1 in 375) Pain associated with blocked vessels, causes
anemia (fatigue) Common where
mosquito-borne malaria is present
PKU Mutation disrupts function of enzyme Leads to high phenylalanine levels in brain
(poisons) Mental retardation, epilepsy Screening newborns (heel prick) 1 in 10,000 Caucasian births Extremely rare in African-Americans Look normal Need low-protein diet,
smelly formulas
Self Quiz: Quick Check for Understanding
1. Which of the following is an X-linked disorder? A. Angelman B. hemophilia c. Down syndrome
2. How is PKU tested for? A. amniocentesis b. heel prick c. X-ray
3. How are CF patients treated? A. testosterone injections b. chest percussions
4. Turner’s Syndrome is A. 45, X b. 46, XX c. 47, XXY
5. Patients with Klinefelter’s Syndrome are A. all male b. all female c. male or female