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Sex chromosomes Most mammals have one pair of sex chromosomes Males Females.

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Presentation on theme: "Sex chromosomes Most mammals have one pair of sex chromosomes Males Females."— Presentation transcript:

1 Sex chromosomes Most mammals have one pair of sex chromosomes Males Females

2 Sex chromosomes Females have two X chromosomes. Males have an X & Y chromosome.

3 Meiosis During meiosis a female can only produce an egg with an X or an X chromosome. During meiosis a male can produce a sperm with an X or a Y chromosome.

4 Meiosis & Punnett Square

5 Normal Karyotype

6 How nondisjunction can result in abnormalities in the number of sex chromosomes... Female Nondisjunction XXX X XXY Y Female (triple X) Female (Turner’s Syndrome) Male (Klinefelter’s Syndrome) Nonviable XX Eggs X Y XY Sperm Male

7 Turner’s syndrome -XO most common sex-chromosome abnormality in females 1 out of every 2500 female births 60,000 females in the U. S. first described in 1938

8 Turner’s syndrome symptoms Young infants & childhood: swollen hands and feet wide and webbed neck drooping eyelids dry eyes

9 Turner’s syndrome symptoms Older females: short height infertility - absence of a menstrual period incomplete development at puberty sparse pubic hair and small breasts broad, flat chest shaped like a shield

10 Possible Complications  Arthritis  Cataracts  Diabetes  Thyroiditis  Heart defects  High blood pressure  Kidney problems  Middle ear infections  Obesity  Scoliosis Alien Autopsy & Turner’s syndrome

11 Klinefelter's syndrome - XXY 1 in 850 newborn males normal physical appearance until puberty first described by Harry F. Klinefelter in 1942

12 Klinefelter's syndrome symptoms tall height abnormal body proportions (long legs, short trunk) sexual problems ・ enlarged breasts little pubic, armpit, and facial hair Infertility - underdeveloped gonads

13 Trisomy X - XXX one in every 1,000 newborn girls girls are born in the U. S. each day Dr. Patricia Jacobs identified the extra X in Trisomy

14 Trisomy X symptoms appearance similar to Klinefelter’s but female tall stature - low weight varying degrees of androgyny learning disability delayed speech & language skills developmental delays normal sexual development

15 XYY syndrome (supermale)

16 1 in 1,000 males first published by Avery A. Sandberg in Buffalo, New York Avery A. SandbergBuffalo, New York1961 increase risk of learning disabilities tall with severe acne aggressive behavior some studies show a higher % of supermales are in prisons normal sexual development and are fertile some medical geneticists question whether the term "syndrome" is appropriate for this condition because its phenotype is normalsyndromephenotype

17 Cat cry syndrome deletion of chromosome 5 1 in 20,000 to 50,000 live births all ethnic backgrounds slightly more common in females first described by Jerome Lejeune in 1963

18 Cat cry syndrome symptoms problems with the larynx and nervous system infant sounds just like a meowing kitten feeding problems because of difficulty swallowing low birth weight and hypotonia(low muscle tone) severe cognitive, speech, and motor delays hyperactivity, aggression, tantrums, and repetitive movements unusual facial features which may change over time

19 Translocation Philadelphia Chromosome (can lead to leukemia) (can lead toleukemia)

20 Down Syndrome Extra chromosome 21

21 Down Syndrome In the US, 1 baby in 800 is born with Down syndrome produces mild to severe mental retardation characterized by an increased susceptibility to many diseases

22 What is the disorder??? aaaaaaaaaaaaaaa a Klinefelter’s Syndrome

23 What is the disorder??? aaaaaaaaaaaaaaa a Down’s Syndrome

24 What is the disorder??? Turner’s Syndrome


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