1. Genetic Disorders
AP Biology

2. Detecting Genetic Disorders
Amniocentesis
Chorionic villus sampling
Karyotype
Sequential Screen (Quad/Triple Screen)
Blood Test

3. Amniocentesis A technique for determining genetic abnormalities in a fetus by the presence of certain chemicals or defective fetal cells in the amniotic fluid, obtained by aspiration from a needle inserted into the uterus.

5. CVS –sample of embryonic cells taken for chorionic villus (placenta) can be done earlier than amniocentesis and results yielded sooner

6. Karyotype
A method of organizing the chromosomes of a cell in relation to number, size, and type. Taken during METAPHASE of Mitosis.

7. Karyotype

8. Normal Male

9. Normal Female

10. NON-DISJUNCTION
Chromosomes fail to separate properly - can occur during meiosis I (all cells affected) or meiosis II (half cells affected)
Aneuploidy - having an abnormal chromosome number
Trisomic/TRISOMY - having 3 chromosomes 2n+1
Monosomic - having 1 chromosome 2n-1
Polyploidy - having move than 2 sets of chromosomes
Triploidy - (3n)
Tetraploidy - (4n) common in plants – usually lethal in animals and humans

11. Nondisjunction Disorders
Down’s Syndrome - Trisomy 21
Edward’s Syndrome - Trisomy 18
Patau’s Syndrome - Trisomy 13
Turner’s Syndrome - X0
Klinefelter’s Syndrome - XXY
Super Male - XYY
Super Female - XXX

12. Down’s Syndrome
Characteristic facial features, low mental ability, stocky build, sometimes heart defects.
Extra copy of chromosome #21 –Trisomy 21

13. Edward’s Syndrome Trisomy 18 Motor and mental retardation
Congenital heart disease
Often dies in infancy

14. Patau’s Syndrome Trisomy 13
Physical abnormalities – cleft palate, polydactaly, microcephaly

15. Turner Syndrome XO Female missing one X chromosome short stature
wide neck with extra skin folds
underdevelopment of sex characteristics – may lead to sterility
non-disjunction of sex chromosomes

16. Klinefelter’s Syndrome XXY
male with extra X chromosome
poor sexual development, may be sterile
subnormal mental ability
other forms are XXYY, XXXY, XXXXY (additional X’s increase the severity of phenotypes and mental retardation)

17. Super Male XYY Jacob’s Syndrome Male with extra Y chromosome
Very tall, can show violent behavior
Prone to acne
Impaired fertility
Mentally normal

18. Chromosomal Abnormalities

20. Short Arm of # 5 Cri – du- chat Cat-like cry
Severe physical and mental abnormalities
nonlethal

21. Gene Mutations Point mutations
Changes in 1 or a few base pairs in a single gene
Substitutions
Base-pair insertions or deletions: - Can result in a frameshift mutation alters the ‘reading frame’ of triplets
THE FAT CAT ATE …
THF ATC ATA TE….

22. Gene Abnormalities Point Substitution Silent – no change in aa
Nonsense – STOP CODON
Missense – change in aa
THE FAT CAT ATE THE RAT  TOE FAT CAT ATE THE RAT
*Insertion/Addition
*Deletion
*May result in a Frame-Shift Mutation
THE FAT CAT ATE THE RAT  THF ATC ATA TET HER AT
(ENTIRE MESSAGE SHIFTS)
Transposons (jumping genes) – transfer of a gene from one locus to another on a chromosome – may unactivated relocated gene – which may produce a point mutation and could result in the elimination of a vital metabolic pathway

24. Sickle Cell Anemia Abnormal hemoglobin
1 aa substitution causes abnormality (point mutation)
Codominance (carrier)
Low oxygen RBC will become crescent shape

25. Inherited Genetic Disorders
Autosomal Dominant
Inherit one allele
Autosomal Recessive
Must inherit two recessive alleles, one from each parent. Parent’s are usually CARRIERS of the disorder
Sex-Linked Disorders
Usually recessive, inherited on X-chromosome
More common in males

26. Autosomal Dominant
Huntington’s Disease
Marfan Syndrome
Achondroplasia

27. Huntington’s Disease Autosomal Dominant Disorder (lethal)
CNS problem
Dementia
Impaired memory
Asymptomatic until
later in life (40)

28. Marfan Syndrome Autosomal Dominant Connective tissue defect
Tall, thin, long arms and legs
Enlarged aorta
Abe Lincoln did NOT have
Marfan Syndrome

29. Achondroplasia Autosomal Dominant Defects in growth of long bones
Form of dwarfism
Short arms and legs but torso of normal size, large head compared to body

30. Autosomal Recessive
PKU
Albinism
Tay Sachs
Cystic Fibrosis

31. PKU Phenylketonuria Autosomal Recessive
Lack enzyme to convert phenylalanine to tyrosine
Buildup of phenylalanine can cause retardation
Test babies at birth
Special diet for phenylketonurics

32. Albinism Lack of pigmentation in skin, hair, eyes
Inability to make melanin
Autosomal recessive

33. Tay-Sachs Autosomal recessive Degeneration of nervous system
No enzyme to break down lipids in brain cells, so they swell and die (death by age 5) - Lethal
High incidence in Ashkenazie Jews
Blood test available to potential parents

34. Cystic Fibrosis
Cystic Fibrosis, incurable hereditary disorder that causes the body to secrete an abnormally thick, sticky mucus that clogs the pancreas and the lungs, leading to problems with breathing and digestion, infection, and ultimately, death.
Common among Caucasians
One of the most common fatal genetic disorders in the United States
Lethal
Autosomal recessive, caused by missing 3 bases/1 aa (phenylalanine) protein does not fold correctly

35. Sex-Linked Traits Gene loci on a sex-linked chromosome
Genes for many sex-linked traits, unrelated to gender, are found on the X chromosome
Follow Mendelian Laws of Inheritance
May be either dominant or recessive
Hemophilia
Duchenne Muscular Dystrophy
Colorblindness

36. Hemophilia Sex-linked recessive disorder
Lack of protein necessary for normal blood clotting

37. Duchenne Muscular Dystrophy
Sex-linked recessive disorder
Absence of muscle protein dystrophin
Progressive muscle deterioration and loss of coordination – most die by age of 20

38. Colorblindness