1. S TANDARD : DESCRIBE TECHNIQUES OF SUCH AS CHROMOSOMAL ANALYSIS TO STUDY GENOMES OF ORGANISMS (B.6H) E SSENTIAL Q UESTION : HOW CAN A KARYOTYPE BENEFIT PARENTS EXPECTING AN OFFSPRING.

2. W HAT EACH OF THE HUMAN CHROMOSOMES LOOK LIKE

3. K ARYOTYPE : A PHOTOMICROGRAPH OF CHROMOSOMES ARRANGED ACCORDING TO A STANDARD CLASSIFICATION

4. I N OTHER WORDS … Chromosomes are digitally arranged so that they are matched with their homologue or “partner” chromosome. Homologue chromosomes are the same size, shape, and carry the same genes, and one is inherited from each parent. They are numbered according to size.

5. S EX DETERMINATION WITH KARYOTYPE This karyotype has 23 exact pairs, which means the person is female. Note that #23 chromosomes are both X.

6. N ORMAL HUMAN MALE Note that #23 chromosomes are X and Y.

7. I S THIS PERSON FEMALE OR MALE ?

8. T RISOMY 21 Abnormality shown in karyotype Note that there are three copies of #21 chromosome. This person has Down Syndrome.

9. P HOTOS OF D OWN S YNDROME PATIENTS FROM THE N ATIONAL D OWN S YNDROME S OCIETY

10. C ORRELATION BETWEEN MOTHER ’ S AGE AND T RISOMY 21 INCIDENCE

11. M ONOSOMY X Abnormality shown in karyotype Note this person only has 1 copy of the X chromosome. This female has Turner’s syndrome.

12. XXY M ALE (E XTRA X)

13. C RI - DU - CHAT Babies with the cry of the cat syndrome have a cry which sounds like that of a cat in distress because the infant’s larynx is improperly developed. Cri-du0chat babies are severely mentally retarded and have a small cranium. The incidences of this syndrome is 1 in 100,000 live births. Caused by a partial deletion of chromosome 5

14. T RISOMY 21, ONE OF THE MOST COMMON CAUSES OF MENTAL RETARDATION IS DUE TO AN EXTRA CHROMOSOME 2`. T HIS RESULTS IN A NUMBER OF CHARACTERISTIC FEATURES, SUCH AS SHORT STATURE, BROAD HANDS, STUBBY FINGERS AND TOES, AND A WIDE ROUNDED FACE. I NDIVIDUALS WITH THIS SYNDROME HAVE A HIGH INCIDENCE OF HEART DEFECTS AND LUKEMIA. T HE AVERAGE RISK OF HAVING A CHILD WITH D OWN ’ S SYNDROME IS 1 IN 750 LIVE BIRTHS. M OTHERS IN THEIR EARLY TWENTIES HAVE A RISK OF 1 IN 1,500, WOMEN OVER 35 HAVE A RISK FACTOR OF 1 IN 70. Down’s Syndrome

15. E DWARD ’ S S YNDROME Trisomy 18 produces severe mental retardation and a highly characteristic pattern of malformations such as elongated skull, a narrow pelvis, rocker bottom feet. Nearly all babies born with this syndrome die in early infancy. The frequency of this syndrome is 1 in 5,000 live births.

16. P ATAU S YNDROME This syndrome (trisomy 13) causes severely abnormal cerebral functions and virtually always leads to death in early infancy. This baby has very pronounced clefts of the lip and palate, broad nose, small cranium and nonfunctional eyes. Heart defects and severe mental retardation are also part of the clinical picture. The frequency is 1 in 15,000 live births.

17. T URNER S YNDROME (XO) This is a result of nondisjunction in meiosis. These girls appear normal before puberty, but as they grow secondary sex characteristics do not develop and no ova are produced. The frequency of this syndrome is 1 in 2,500 live births.

18. K LINEFELTER S YNDROME (XXY) This is a result of nondisjunction in meiosis. The frequency of this condition is 1 in 1,000 live male births. Characteristics include a tall stature and sterility. Men appear normal in other ways.

19. J ACOBS (XYY) A chromosome aberration which is caused by nondisjunction of the Y chromosome during the second phase of meiosis. Occurrence is 1 in 1,000 live male births. Men with this abnormality are tall and have low mental ability.

20. T RIPLE X Occurs at a frequency of 1 in 1,000 female live births. No specific abnormalities are associated with this condition. The vast majority of women with this condition are normal mentally and physically and are fertile.