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Genetic Disorders AP Biology. Detecting Genetic Disorders Amniocentesis Amniocentesis Chorionic villus sampling Chorionic villus sampling Karyotype Karyotype.

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Presentation on theme: "Genetic Disorders AP Biology. Detecting Genetic Disorders Amniocentesis Amniocentesis Chorionic villus sampling Chorionic villus sampling Karyotype Karyotype."— Presentation transcript:

1 Genetic Disorders AP Biology

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

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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. 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) 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 Aneuploidy - having an abnormal chromosome number Trisomic/TRISOMY - having 3 chromosomes 2n+1 Trisomic/TRISOMY - having 3 chromosomes 2n+1 Monosomic - having 1 chromosome 2n-1 Monosomic - having 1 chromosome 2n-1 Polyploidy - having move than 2 sets of chromosomes Polyploidy - having move than 2 sets of chromosomes Triploidy - (3n) Triploidy - (3n) Tetraploidy - (4n) common in plants – usually lethal in animals and humans Tetraploidy - (4n) common in plants – usually lethal in animals and humans

11 Nondisjunction Disorders Down’s Syndrome - Trisomy 21 Down’s Syndrome - Trisomy 21 Edward’s Syndrome - Trisomy 18 Edward’s Syndrome - Trisomy 18 Patau’s Syndrome - Trisomy 13 Patau’s Syndrome - Trisomy 13 Turner’s Syndrome - X0 Turner’s Syndrome - X0 Klinefelter’s Syndrome - XXY Klinefelter’s Syndrome - XXY Super Male - XYY Super Male - XYY Super Female - XXX 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 Trisomy 18 Motor and mental retardation Motor and mental retardation Congenital heart disease Congenital heart disease Often dies in infancy Often dies in infancy

14 Patau’s Syndrome Trisomy 13 Trisomy 13 Physical abnormalities – cleft palate, polydactaly, microcephaly 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 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 XYY Jacob’s Syndrome Male with extra Y chromosome Male with extra Y chromosome Very tall, can show violent behavior Very tall, can show violent behavior Prone to acne Prone to acne Impaired fertility Impaired fertility Mentally normal Mentally normal

18 Chromosomal Abnormalities

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

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

22 Gene Abnormalities Point Point Substitution 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 *Insertion/Addition *Deletion *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

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

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

26 Autosomal Dominant Huntington’s Disease Huntington’s Disease Marfan Syndrome Marfan Syndrome Achondroplasia Achondroplasia

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

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

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

30 Autosomal Recessive PKU PKU Albinism Albinism Tay Sachs Tay Sachs Cystic Fibrosis Cystic Fibrosis

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

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

33 Tay-Sachs Autosomal recessive Autosomal recessive Degeneration of nervous system Degeneration of nervous system No enzyme to break down lipids in brain cells, so they swell and die (death by age 5) - Lethal No enzyme to break down lipids in brain cells, so they swell and die (death by age 5) - Lethal High incidence in Ashkenazie Jews High incidence in Ashkenazie Jews Blood test available to potential parents 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. 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.pancreas lungspancreas lungs Common among Caucasians Common among Caucasians One of the most common fatal genetic disorders in the United States One of the most common fatal genetic disorders in the United States genetic disorders genetic disorders Lethal Lethal Autosomal recessive, caused by missing 3 bases/1 aa (phenylalanine) protein does not fold correctly 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 Gene loci on a sex-linked chromosome Genes for many sex-linked traits, unrelated to gender, are found on the X chromosome Genes for many sex-linked traits, unrelated to gender, are found on the X chromosome Follow Mendelian Laws of Inheritance Follow Mendelian Laws of Inheritance May be either dominant or recessive May be either dominant or recessive Hemophilia Hemophilia Duchenne Muscular Dystrophy Duchenne Muscular Dystrophy Colorblindness Colorblindness

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

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

38 Colorblindness


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