May 15

8:50 a.m.

Make Up Exam

For only one missed midterm

Bring scantron and I.D.

http://images.google.com/imgres?imgurl=www.goldenlands.com/Fox%2520network/simpsons/opcs/fullsize/Homer_Marge_opcC1394.jpg&imgrefurl=http://www.goldenlands.com/Fox%2520network/simpsons/simpsonopc.html&h=700&w=694&prev=/images%3Fq%3Dhomer%2Band%2Bmarge%2Bsimpson%26start%3D20%26svnum%3D10%26hl%3Den%26lr%3D%26ie%3DUTF-8%26safe%3Doff%26sa%3DN

Sex Determination in Humans

Sex Determination in Humans – 5 stages

Chromosomal Determination

Gonad Differentiation

Anatomical Differentiation

Brain Differentiation

Socialization

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

EXAM

Human Male Karyotype, XY

http://www.amnh.org/learn/musings/FA01/ia/HW_01.jpg

Chromosomes 1-22 are autosomes or somatic chromosomes; non-sex chromosomes

XY are the sex chromosomes

Normal Human Female Karyotype; XX

22 pairs of autosomes

1 pair of sex chromosomes, XX

Y

X

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

X Y

Additional genes found on Y chromosomeInability 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

Male anatomy,

physiology, behavior

Female anatomy,

physiology, behavior

Y chromosome

X chromosome

SRY (H-Y) protein

SRY (HY) gene

w/o SRY (HY) gene

EXAM

H-Y Gene w/o H-Y Gene

Primitive gonad or ovotestes = unspecialized

Testes ovary

Testosterone Estrogens

2. 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

2.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.

Male Female

Mostly testosterone

Little estrogen

Mostly Estrogens

Little testosterone

Some abnormalities associated with X and Y chromosomes

X Y

H-Y gene

H-Y gene crosses over to X chromosome

X Y

Crossing over of H-Y gene

Spermatogenesis

Sperm with X with H-Y gene

Egg with normal X without H-Y gene

Zygote:

XX (genetic female)

Phenotype = male, because of the H-Y gene

X

X

X

X

Sperm with Y without H-Y gene

Egg with normal X without H-Y gene

Zygote:

XY = genetic male

Phenotype = female because of absence of H-Y gene

Y

X

Y

X

Conclusion:

Absence of H-Y gene usually = female;

female is automatic unless H-Y gene is present

EXAM

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

Primary Oocyte

Secondary Oocyte

ovum

zygote

sperm

Non-disjunction

Extra black chromosome Missing a black chromosome

zygote

Klinefelter’s Syndrome

Klinefelter’s Syndrome – XXY+ 22 pairs of autosomes male with some female characteristics

XX Egg + 22

autosomes

Y Sperm + 22

autosomes

XXY Zygote + 44

autosomes

1. Normal male until puberty, 2. Testes not normal, 3. Tall, 4. Female musculature, 5. Some breast development, 6. High pitched voice, 7. Usually sterile, 8. XXXY more extreme

EXAM

Trisomy X Syndrome – XXX+ 22 pairs of autosomes female

XX Egg + 22

autosomes

X Sperm + 22

autosomes

XXY Zygote + 44 autosomes

1. Normal Female, 2, Normal appearance, 3. May be sterile or fertile, 4. May have mental retardation, 5. 1 in 1200 births, 6. XXXX more extreme

EXAM

Turner’s Syndrome = 22 pairs of autosomes and X0

Turner’s Syndrome – X0 + 22 pairs of autosomes female

No X Egg + 22

autosomes

X Sperm + 22

autosomes

X0 Zygote + 44

autosomes

EXAM

Characteristics:

1. Normal female until puberty,

2. Lack of normal ovary development,

3. sterile

4. Remain childlike throughout life

5. Normal intelligence

6. 1 per 2500 births

XYY Syndrome – XYY + 22 pairs of autosomes Male

X Egg + 22

autosomes

YY Sperm + 22

autosomes

XYY Zygote + 44 autosomes

EXAM

Male

Lower than normal intelligence

Tall

Aggressive – disproven

Prison - disproven

Early Death Syndrome – Y0 + 22 pairs of autosomes Male ?

No X Egg + 22

autosomes

Y Sperm + 22

autosomes

Y0 Zygote + 44

autosomes

EXAM

Dies as embryo

Too many genes missing with X

All chromosomes are capable of forming a trisomy condition.

The most common is chromosome 21.

Trisomy 21 is also known as Down’s Syndrome

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 12-50 years later

More ionizing radiation picked up in older woman’s lifetime resulting

in nondisjuctions

All chromosomes can have trisomy

Primary Oocyte

Secondary Oocyte

ovum

zygote

sperm

Non-disjunction

Extra black chromosome Missing a black chromosome

zygote

21 21

2121

2121

21

21

21 21

21 21

21

In Trisomy 21, chromosomes 21 do not separate after crossover

Younger women

Older women

2121

EXAM

Trisomy 21 increases with Mother’s age

Triploid (3N) male karyotype – individual appeared normal except for slightly smaller lower jaw.

This person also has Klinefelter, XXY

Triploid Watermelon - seedless

Triploid carp - sterile

http://www.mun.ca/biology/scarr/Barr_Bodies.jpg

Barr Body inactivates one of the X

chromosomes in XX cells after embryo is properly developed

sexually

XGreen

XG XP

XPink

XPXG

Mitosis Mitosis

Active XP cell line Active XG cell line

Female mosaic

XX zygote

Mitosis

XGreen

XG XG

XGreen

XGXG

Mitosis Mitosis

Active XG cell line Active XG cell line

Female all green

XX zygote

Mitosis

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

http://www.bitein.com/images/reshma02.jpg

No teeth, no sweat glands

XNXn female

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

XBXOYBlack and orange, male (Klinefelter, Calico)

XBXO

Conclusion – always one fewer Barr Body than X chromosomes

EXAM

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