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KARYOTYPE AND GENETIC DISORDERS H. Biology. Chromosomes Determine Your Gender Humans have 23 pairs of chromosomes autosomes22 pairs are autosomes (chromosomes.

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Presentation on theme: "KARYOTYPE AND GENETIC DISORDERS H. Biology. Chromosomes Determine Your Gender Humans have 23 pairs of chromosomes autosomes22 pairs are autosomes (chromosomes."— Presentation transcript:

1 KARYOTYPE AND GENETIC DISORDERS H. Biology

2 Chromosomes Determine Your Gender Humans have 23 pairs of chromosomes autosomes22 pairs are autosomes (chromosomes that are NOT involved in making gender) Also called homologous chromosome pairs 1 pair are sex chromosomes (NOT HOMOLOGOUS; different genes) The sex chromosomes are “X” and “Y” “XX” is a girl “XY” is a boy X Y Y X Egg cells ALWAYS have “X” chromosome

3 5 µm Pair of homologous chromosomes Centromere Sister chromatids A karyotype an ordered, visual representation of ALL chromosomes in a human cell Arranged according to homologous pairs

4 a REAL view… wow!!!

5 What is a genetic disorder? What causes a genetic disorder? Caused by an abnormality in an individual’s DNA How do these abnormalities occur? 1)Non-disjunction Addition or subtraction of chromosome or set of chromosomes 2)Mutations Change to DNA sequence (gene)

6 Abnormal Chromosome Number When nondisjunction occurs Pairs of homologous chromosomes do NOT separate normally during meiosis Gametes contain 2 copies or NO copies of a particular chromosome What are some disorders caused by non-disjunction? Downs Syndrome Trisomy 21 Klinefelter’s Syndrome XXY Turner Syndrome Monosomy X

7 What happens when meiosis goes wrong?  NONDISJUNCTION!!!

8 Figure 15.12a, b Meiosis I Nondisjunction Meiosis II Nondisjunction Gametes n + 1 n  1 n – 1 n + 1n –1 n n Number of chromosomes Nondisjunction of homologous chromosomes in meiosis I Nondisjunction of sister chromatids in meiosis II (a) (b)

9 Aneuploidy Results from the fertilization of gametes in which nondisjunction occurred abnormal number Offspring have an abnormal number of a particular chromosome

10 What are some disorders caused by non-disjunction? Downs Syndrome Trisomy 21 Kleinfelter’s Syndrome XXY Edwards Syndrome Trisomy 18 Patau Syndrome Trisomy 13 Turner Syndrome Monosomy X

11 1.) Trisomy 18-Edwards Syndrome

12 2.) Trisomy-13: Usually Fatal

13 3.) Klinefelter - XXY

14 Klinefelter syndrome a result of an extra chromosome in a male, producing XXY individuals 1/2000 live births

15 XYY individuals

16 Triple X Syndrome XXX individuals Females Healthy Same phenotype as XX individuals 1/1000 live births

17 4.) Turner Syndrome

18 Turner syndrome Is the result of monosomy X, producing an X0 karyotype 1/5000 live births Only known monosomy in humans Normal intelligence Sterile

19 5.) Trisomy 21

20 Human Disorders Due to Chromosomal Alterations Down syndrome Is usually the result of an extra chromosome 21 trisomy 21

21 What are some disorders caused by mutations? Sickle cell anemia (recessive) Cystic fibrosis (recessive) Maple syrup urine disorder (recessive) Congenital hypothyroidism (recessive) Huntington’s Disease (dominant)

22 Cystic Fibrosis Example of recessive disorder Affect mostly people of European descent Symptoms Mucus buildup in the some internal organs Abnormal absorption of nutrients in the small intestine

23 Sickle Cell Anemia o Another recessive disorder o Affects one out of 400 African-Americans o Hemoglobin is the O2 carrying protein in red blood cells o SCA is an inherited blood disease where hemoglobin clumps together  causes red blood cells to stiffen and curl into a sickle/crescent shape o Because of this, the RBC cannot transport O2 effectively Symptoms Physical weakness, pain, organ damage, and even paralysis

24 Human Chromosomal Disorders Recessive Disorders Cystic Fibrosis Excess mucus in lungs, digestive tract, liver More susceptible to pneumonia, infection Early death ~ average age of 37 Tay-Sachs Lipid accumulation in brain cells, mental retardation Blindness, death in childhood Dominant Disorder Huntington’s disease Deterioration of nervous system, uncontrollable movements Develops in middle age, death soon after 24

25 Dominantly Inherited Disorders Some human disorders Are due to dominant alleles  only need 1 dominant allele Example is achondroplasia Form of dwarfism  lethal when homozygous for the dominant allele

26 Another Dominant Disorder Huntington’s disease (HD) degenerative disease of nervous system No obvious phenotypic effects until about 35 to 40 years of age HD Normal

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