1. For only one missed midterm
May 15
8:50 a.m.
Make Up Exam
For only one missed midterm
Bring scantron and I.D.

3. Sex Determination in Humans

4. Sex Determination in Humans – 5 stages
Chromosomal Determination
Gonad Differentiation
Anatomical Differentiation
Brain Differentiation
Socialization

5. Chromosomal Sex Determination Humans: 23 pairs of Chromosomes
EXAM
Chromosomal Sex Determination
Humans: 23 pairs of Chromosomes
22 pairs of Autosomes or Somatic Chromosomes (same in both sexes)
1 pair of Sex Chromosomes
Males:
1 Y, 1 X = XY
Females:
2 X = XX

6. Human Male Karyotype, XY
Chromosomes 1-22 are autosomes or somatic chromosomes; non-sex chromosomes
XY are the sex chromosomes

7. Normal Human Female Karyotype; XX
22 pairs of autosomes
1 pair of sex chromosomes, XX

8. X Y

9. Y chromosome has less than 100 genes ……………….. One gene is for ……

10. Additional genes found on Y chromosome
Inability to see and hear the obvious gene
Inability to express affection over the phone gene
Posturing in presence of other males gene
Refusal to ask questions when lost gene
Channel flipping gene
Male Sports Bonding gene
Addiction to death and destruction movies gene
Preadolescent rock throwing gene
Preadolescent attraction to spiders and insects gene
Spitting gene X Y

11. Male anatomy, physiology, behavior
EXAM
Y chromosome
Male anatomy, physiology, behavior
SRY (HY) gene
SRY (H-Y) protein
X chromosome
Female anatomy, physiology, behavior
w/o SRY (HY) gene

12. Testosterone Estrogens
Primitive gonad or ovotestes = unspecialized
H-Y Gene
w/o H-Y Gene
Testes
ovary
Testosterone
Estrogens

13. Gonad Differentiation - Male
H-Y or SRY Gene (on Y Chromosome)
H-Y Protein (SRY protein)
Inner part of ovotestes becomes testes
Testes makes male hormones
Male sex organs,
secondary sex characteristics (muscle, skeleton),
Brain development (for constant production of sperm) at 6 weeks

14. Gonad Differentiation – FemaleXX
Absence of Y chromosome (no H-Y gene)
Outer ovotestes develops into ovary at about week 12
Ovary produces female hormones:
~ sex organs
~ secondary sexual characteristics (muscle, skeleton)
~ absence of male hormones at week 6 allows brain to develop menstrual cycle at puberty.

15. Female Male Little estrogen Little testosterone Mostly testosterone
Mostly Estrogens
Female
Male

16. Some abnormalities associated with X and Y chromosomes
Crossing over of H-Y gene
X Y
X Y
Spermatogenesis
H-Y gene
H-Y gene crosses over to X chromosome

17. Sperm with X with H-Y gene
Zygote:
XX (genetic female)
Phenotype = male, because of the H-Y gene
Egg with normal X without H-Y gene

18. Sperm with Y without H-Y geneX X
Zygote:
XY = genetic male
Phenotype = female because of absence of H-Y gene
Egg with normal X without H-Y gene

19. Absence of H-Y gene usually = female;
EXAM
Conclusion:
Absence of H-Y gene usually = female;
female is automatic unless H-Y gene is present

20. Another Chromosomal Abnormality – Androgen Insensitivity
XY Embryo
Faulty Processing of testosterone
Embryo not conditioned as male
Embryo automatically develops into normal looking female
Develops into female with XY chromosomes
Normal breast development
no uterus
no oviducts
vagina present
internal testes present
no sperm

21. Extra black chromosome Missing a black chromosome
Non-disjunction
Primary Oocyte
Secondary Oocyte
ovum
zygote
zygote
Extra black chromosome
Missing a black chromosome
sperm

22. Klinefelter’s Syndrome

23. Klinefelter’s Syndrome – XXY+ 22 pairs of autosomes male with some female characteristics
EXAM
XX Egg autosomes
Y Sperm autosomes
1. Normal male until puberty, Testes not normal, Tall, Female musculature, Some breast development, High pitched voice, Usually sterile, XXXY more extreme
XXY Zygote autosomes

25. Trisomy X Syndrome – XXX+ 22 pairs of autosomes female EXAM
XX Egg autosomes
X Sperm autosomes
1. Normal Female, , Normal appearance, May be sterile or fertile, May have mental retardation, in 1200 births, XXXX more extreme
XXY Zygote autosomes

26. Turner’s Syndrome = 22 pairs of autosomes and X0

27. Turner’s Syndrome – X0 + 22 pairs of autosomes female EXAM
No X Egg autosomes
X Sperm autosomes
Characteristics:
Normal female until puberty,
Lack of normal ovary development,
sterile
Remain childlike throughout life
Normal intelligence
1 per 2500 births
X0 Zygote autosomes

29. XYY Syndrome – XYY + 22 pairs of autosomes Male EXAM
X Egg autosomes
YY Sperm autosomes
Male
Lower than normal intelligence
Tall
Aggressive – disproven
Prison - disproven
XYY Zygote autosomes

30. Early Death Syndrome – Y0 + 22 pairs of autosomes Male ? EXAM
No X Egg autosomes
Y Sperm autosomes
Dies as embryo
Too many genes missing with X
Y0 Zygote autosomes

31. All chromosomes are capable of forming a trisomy condition.
The most common is chromosome 21.
Trisomy 21 is also known as Down’s Syndrome

32. Trisomy 21 – Down’s Syndrome 3 chromosome #21
Results in physical defects and mental retardation
Frequency increases with mother’s age
Why?
Prophase I occurs before birth, Anaphase I occurs years later
More ionizing radiation picked up in older woman’s lifetime resulting in nondisjuctions
All chromosomes can have trisomy

33. Extra black chromosome Missing a black chromosome
Non-disjunction
Primary Oocyte 21 21
Secondary Oocyte 21 21 21 21 21 21
ovum 21 21 21
zygote 21
zygote 21
Extra black chromosome
Missing a black chromosome
sperm

34. In Trisomy 21, chromosomes 21 do not separate after crossover
Younger women 21 21
Older women

35. Trisomy 21 increases with Mother’s age
EXAM
Trisomy 21 increases with Mother’s age

37. Triploid (3N) male karyotype – individual appeared normal except for slightly smaller lower jaw.
This person also has Klinefelter, XXY

39. Triploid Watermelon - seedless Triploid carp - sterile

40. Barr Body inactivates one of the X chromosomes in XX cells after embryo is properly developed sexually

41. XGreen XPink XG XP XG XP XX zygote Mitosis Mitosis Mitosis
Active XG cell line
Active XP cell line
Female mosaic

42. XGreen XGreen XG XG XG XG
XX zygote
Mitosis XG XG XG XG
Mitosis
Mitosis
Active XG cell line
Active XG cell line
Female all green

43. Anhidrotic Ectodermal Dysplasia:
N = dominant, normal allele on X chromosome
n = recessive allele carried on X chromosome resulting in no teeth and no sweat glands
XNXN normal female
XnXn female with few or no teeth and no sweat glands
XNXn female
parts of jaw with teeth and parts without teeth
parts of skin with sweat glands, parts without sweat glands.
XNY normal male
XnY male with no teeth and no sweat glands

44. No teeth, no sweat glands
XNXn female

45. Calico Cats (normally all females)
B = allele for black fur, on X chromosome
O = allele for orange fur, on X chromosome
XBXB All black fur, female cat
XOXO All orange fur, female cat
XBXO Black and orange, female cat (Calico)
XBY Black, male cat
XOY Orange, male cat
XBXOY Black and orange, male (Klinefelter, Calico)
XBXO

46. Conclusion – always one fewer Barr Body than X chromosomes
EXAM

47. Notice that two of the X chromosomes have Barr bodies causing them to be inactive