Embed Size (px)
Citation preview
Sex Determination&
Nondisjunction Disorders
April 21, 2023
April 21, 2023
KaryotypeHuman 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 21, 2023
Female Karyotype
XX homologous pair 2 sets of genes for every
trait
April 21, 2023
Sex Chromosomes
XY not homologous (no
pair) each one contains
different genes males only have 1 copy
of genes on X & Y chromosome
April 21, 2023
Sex Determination
X XX YWho determines the gender of offspring in humans?all eggs carry one X chromosome½ of sperm carry one X chromosomes½ of sperm carry one Y chromosomesTherefore:
male determines the gender
meiosis
XXXY
X XX Y
eggs sperm
April 21, 2023
Nondisjunction Disorders
anaphase I
April 21, 2023
Nondisjunction DisordersNondisjunction: 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 21, 2023
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 21, 2023
Chromosomal AbnormalitiesChromosomal Abnormalities occur when a normal gamete (n = ___)joins with a
gamete that has:
1. n + 1: individual will have ______________________
2. n - 1: individual will have ______________________
in either case the resulting individual will suffer from some disabilities depending on which chromosomes are involved
(24)(1 chromosome too many)
47
45 (1 chromosome less)(22)
23
April 21, 2023
Nondisjunction Disorders
Common Examples:
1.Down Syndrome trisomy 21
2.Klinefelter’s syndrome XXY
3.Turner’s syndrome X0 monosomy
4.Trisomic female (super female) XXX
5.Jacob’s syndrome (super male) XYY
male
female
(47)
(47)
(47)
(47)
(45)
April 21, 2023
Chromosomal Abnormalities
Down Syndrome trisomy 21
April 21, 2023
Chromosomal Abnormalities Down Syndrome
developmental delays
physical abnormalities
short folds around
eyes stubby fingers &
toes large protruding
tongue weak muscles heart defects
April 21, 2023
Chromosomal Abnormalities
Klinefelter’s syndrome ●XXY●male
April 21, 2023
Chromosomal Abnormalities
Klinefelter’s syndrome ● tall●small testicles●after puberty develop
some feminine traits (ex. breasts)
●sterile
April 21, 2023
Chromosomal Abnormalities
Trisomic Female●XXX●super female●have very few
problems●most are fertile
April 21, 2023
Chromosomal Abnormalities
Turner’s syndrome●XO● female
April 21, 2023
Chromosomal Abnormalities
Turner’s syndrome●short● thick neck●never goes
through puberty●sterile
15 year old
April 21, 2023
Chromosomal Abnormalities
Jacob’s syndrome ●XYY●super male●very tall● low mental ability●often aggressive
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 21, 2023
April 21, 2023
Homework
• Karyotype Assignment
