Sex Determination & Nondisjunction Disorders April 24, 2017

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

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

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

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

Nondisjunction Disorders anaphase I April 24, 2017

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

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 http://pregnancy.healthguru.com/content/video/watch/100062/Understanding_Amniocentesis?HG_Google_Video_Sitemap= April 24, 2017

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

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

Chromosomal Abnormalities Down Syndrome trisomy 21 April 24, 2017

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

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

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

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

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

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

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

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

Homework Karyotype Assignment April 24, 2017