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Presentation on theme: "KARYOTYPE AND GENETIC DISORDERS"— Presentation transcript:

H. Biology

2 Chromosomes Determine Your Gender
Humans have 23 pairs of chromosomes 22 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 Egg cells ALWAYS have “X” chromosome Y X Y

3 A karyotype 5 µm Pair of homologous chromosomes Centromere Sister chromatids 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? Non-disjunction Addition or subtraction of chromosome or set of chromosomes 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 Nondisjunction of sister chromatids in meiosis II
Figure 15.12a, b Meiosis I Nondisjunction Meiosis II Gametes n + 1 n  1 n – 1 n –1 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 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
Half of infants with this condition do not survive beyond the first week of life. Some children have survived to the teenage years, but with serious medical and developmental problems. Trisomy 18 is a somewhat common syndrome. It is three times more common in girls than boys. kidney malformations, structural heart defects at birth, intestines protruding outside the body (omphalocele), mental retardation, developmental delays, growth deficiency, feeding difficulties, breathing difficulties, and arthrogryposis (a muscle disorder that causes multiple joint contractures at birth)

12 2.) Trisomy-13: Usually Fatal
Trisomy 13 – Patau Syndrome More than 80% of children with trisomy 13 die in the first year. Mental retardation and motor disorder Structural eye defects including cleft iris, Cleft palate, Polydactyly Polydactyly (extra digits) Low-set ears[3] Prominent heel Deformed feet known as rocker-bottom feet Omphalocele (abdominal defect) Abnormal palm pattern Overlapping of fingers over thumb Kidney defects Heart defects (ventricular septal defect)

13 3.) Klinefelter - XXY Klinefelters
As babies and children, XXY males may have weaker muscles and reduced strength. As they grow older, they tend to become taller than average. They may have less muscle control and coordination than other boys their age.[4] During puberty, the physical traits of the syndrome become more evident; because these boys do not produce as much testosterone as other boys, they have a less muscular body, less facial and body hair, and broader hips. As teens, XXY males may have larger breasts, weaker bones, and a lower energy level than other boys. By adulthood, XXY males look similar to males without the condition, although they are often taller. In adults, possible characteristics vary widely and include little to no signs of affectedness, a lanky, youthful build and facial appearance, or a rounded body type with some degree of gynecomastia (increased breast tissue).[9] Gynecomastia is present to some extent in about a third of affected individuals, a slightly higher percentage than in the XY population. About 10% of XXY males have gynecomastia noticeable enough that they may choose to have cosmetic surgery.[3] Affected males are often infertile, or may have reduced fertility. Advanced reproductive assistance is sometimes possible.[10]

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 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) Maple syrup urine – found in mnemonites  cant digest amino acids, so their urine smells sweet because the amino acids come out in urine Decrease in thyroid hormonal production/thyroid gland missing/thyroid gland not fully formed

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 Another recessive disorder
Affects one out of 400 African-Americans Hemoglobin is the O2 carrying protein in red blood cells SCA is an inherited blood disease where hemoglobin clumps together  causes red blood cells to stiffen and curl into a sickle/crescent shape 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

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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