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Sex Determination & Nondisjunction Disorders

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Presentation on theme: "Sex Determination & Nondisjunction Disorders"— Presentation transcript:

1 Sex Determination & Nondisjunction Disorders
April 24, 2017

2 Karyotype Human Karyotype:
46 chromosomes organized in 23 pairs in order of decreasing size Pairs # 1-22: autosomes somatic (body) chromosomes all 22 pairs are homologous Pair # 23: sex chromosomes contain genes that code for sexual characteristics April 24, 2017

3 Female Karyotype XX homologous pair 2 sets of genes for every trait
April 24, 2017

4 Sex Chromosomes XY not homologous (no pair)
each one contains different genes males only have 1 copy of genes on X & Y chromosome April 24, 2017

5 Sex Determination X X X Y
meiosis X Y X X eggs sperm X X X Y Who determines the gender of offspring in humans? all eggs carry one X chromosome ½ of sperm carry one X chromosomes ½ of sperm carry one Y chromosomes Therefore: male determines the gender April 24, 2017

6 Nondisjunction Disorders
anaphase I April 24, 2017

7 Nondisjunction Disorders
one pair of homologous chromosome doesn’t separate during anaphase I Result: ½ gametes have one chromosome too few other ½ gametes have one chromosome too many in females, nondisjunction occurs more often if >35 years old missing one chromosome one extra chromosome April 24, 2017

8 Nondisjunction Disorders
amniocentesis : recommended for all women over 35 years old fetal cells removed with a needle from amniotic fluid karyotype of fetal cells examined for nondisjunction disorders April 24, 2017

9 Chromosomal Abnormalities
occur when a normal gamete (n = ___)joins with a gamete that has: n + 1: individual will have ______________________ n - 1: in either case the resulting individual will suffer from some disabilities depending on which chromosomes are involved 23 (24) 47 (1 chromosome too many) (22) 45 (1 chromosome less) April 24, 2017

10 Nondisjunction Disorders
Common Examples: Down Syndrome trisomy 21 Klinefelter’s syndrome XXY Turner’s syndrome X0 monosomy Trisomic female (super female) XXX Jacob’s syndrome (super male) XYY (47) male (47) female (45) (47) (47) April 24, 2017

11 Chromosomal Abnormalities
Down Syndrome trisomy 21 April 24, 2017

12 Chromosomal Abnormalities
Down Syndrome developmental delays physical abnormalities short folds around eyes stubby fingers & toes large protruding tongue weak muscles heart defects April 24, 2017

13 Chromosomal Abnormalities
Klinefelter’s syndrome XXY male April 24, 2017

14 Chromosomal Abnormalities
Klinefelter’s syndrome tall small testicles after puberty develop some feminine traits (ex. breasts) sterile April 24, 2017

15 Chromosomal Abnormalities
Trisomic Female XXX super female have very few problems most are fertile April 24, 2017

16 Chromosomal Abnormalities
Turner’s syndrome XO female April 24, 2017

17 Chromosomal Abnormalities
Turner’s syndrome short thick neck never goes through puberty sterile 15 year old April 24, 2017

18 Chromosomal Abnormalities
Jacob’s syndrome XYY super male very tall low mental ability often aggressive April 24, 2017

19 FUN QUIZ Fill out the Atypical Meiosis Sheet 7 min
Switch with the person behind you 1 mark for every fill in the blank correct Total in top right hand corner Hand in to me! April 24, 2017

20 Homework Karyotype Assignment April 24, 2017

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