1. Mendel, Morgan and Beyond
I. Mendelian Genetics
A. Gregor Mendel and the Garden Pea Experiments

2. B. Garden Pea and the Seven Traits Studied in the Garden Pea Plant

3. C. Flower Structure and Function
A. Carpel Structure
B. Stamen Structure
C. Pollination
D. Fertilization

4. II. Mendel’s Genetic Crosses
A. Producing Purebred Garden Pea Plants

5. B. Monohybrid Crosses
T = tall stem; t = short stem
TT x tt parental generation (P) cross pollination
T T t t gametes
Tt first filial generation (F1)
Tt x Tt F1 self fertilization
T t T t gametes
second filial generation (F2)
3:1 phenotypic ratio

6. C. Dihybrid Crosses
R = round seed, r = round seed; Y = yellow seed, y = green seed
RRYY x rryy P cross pollination
RY RY ry ry gametes
RrYy F1
RrYy x RtYy F1 self pollination
RY Ry rY ry RY Ry rY ry F1 gametes

7. F2 phenotypic ratio 9:3:3:1

8. III. Genetics Mendel Missed
A. Incomplete Dominance- neither allele dominant
1. New phenotypes emerge in the F1 not found in parents
2. Four o’clock flower inheritance
r = red flower color, w = white flower color
rr x ww P cross pollination
r w gametes
rw F1
rw X rw self pollination of F1
r w r w F1 gametes
F2 phenotypic ratio
1:2:1

9. Examples of incomplete dominance in four o-clock flowers
1:2:1 phenotypic ratio White - Pink - Red flowers

10. B. Codominance- both alleles are dominant
1. Both phenotypes appear- neither is dominant
2. Blood types in humans
A B AB O

11. Codominance in tulips and cattle
Bicolor tulip Hybrid roan cattle

12. C. Multiple Alleles
1. Exists when there are more than two alleles for a given trait
2. Blood typing in humans is an example of multiple alleles
2. Three blood type alleles: A, B and O alleles
3. When doing genotyping for blood types, I stands for
immunoglobulinandthe superscript the blootd type allele
A A A B B B A B
I I I i I I I i I I i i
A A B B AB O

13. D. Pleiotrophy
1. Pleiotropy occurs when one gene influences multiple phenotypic traits
2. Sickle cell trait

14. E. Epistasis
1. The gene whose phenotype is expressed is called epistatic, while the
phenotype altered or suppressed is called hypostatic
2. Labrador retriever coat color
B = black, b = chocolate; E = color deposition, e = no color deposition
BBEE BbEE BBEe BbEe bbEE bbEe BBee Bbee bbee
(no color deposited even though the color coat gene is present)

15. F. Penetrance
1. The likelihood a given gene will result in disease
2. If half (50%) of the people with the polydactyly have the
disease, the penetrance of the polydactyly gene is 0.5

16. G. Expressivity
1. Variable expressivity shown by 10 grades of piebald spotting in
beagles
2. Each of these dogs has the allele responsible for piebald spots in dogs

17. H. Polygenic Inheritance
1. More than one set of genes determine a characteristic
2. Skin pigmentation in humans displays polygenic inheritance

18. Genes A, B, C determine skin color in humans
Genotypic combinations:
AABBCC
AaBBCC
AABbCC
AABBCc
aaBBCC
aaBbCC
aaBBCc
aabbcc

19. IV. Thomas Hunt Morgan
A. The Morgan “Fly Lab” at Columbia University
1. Following the rediscovery of Mendelian inheritance in
1900, Morgan's research moved to the study of
mutation in the fruit fly, Drosophila melanogaster
2. In “Fly Room” at Columbia University, Morgan was able
to demonstrate that genes are carried on chromosomes
and are the mechanical basis of heredity
3. Awarded the Nobel Prize in Physiology or Medicine in
1933 for discoveries relating the role the chromosome plays in heredity

20. B. Why Drosophila melanogaster?
- short life cycle- 10-14 days
-inexpensive to culture
-sexes easily discerned
-only four pairs of chromosomes
- need little room to culture
-sexes easily discerned

22. Female fruit fly layer an egg

23. C. Sex Linkage and Sex Chromosomes
1. Chromosomes of Drosophila melanogaster
2. Examples of sex-linkage
-white eye color in fruit flies
-color blindness in humans
-hemophilia
D. Determination of eye color in Drosophila
1. Eye color mutants (clockwise): brown,
sepia, cinnabar, vermilion, white, and
apricot
2. Eye color is determined by two
biochemical pathways which makes the
many colors found in Drosophila eye
color mutants

24. E. Sex Determination and Chromosomes
1. X-Y System in Mammals
2. X-0 System in Grasshoppers, Cockroaches, and other Insects
3. Z-W System in Birds, Some Fishes, and Some Insects
4. Haplo-Diploid System in Bees and Ants
F. Nondisjunction
1. Can lead to abnormal chromosome numbers

25. G. Chromosome Map of Drosophila

26. E. X Chromosome Inactivation
1. Barr body phenomenon

27. 2. Calico cat are all female due to the orange and black coat color
gene residing on the X chromosome only

28. Tortoise shell cat

29. VI. Chromosome Aberrations
A. Aneuploidy
1. Abnormal number of chromosomes
B. Trisomy
1. 2n + 1
C. Monosomy
1. 2n – 1
D. Sex Chromosome Abnormalities
1. Klinefelter’s syndrome XXY
2. Turner’s syndrome XO
3. Trisomy X

30. Trisomy X XYY

31. Klinefelter’s syndrome

32. Turner’s syndrome

33. E. Down’s Syndrome

34. VII. Sex Chromosomes and Inheritance
A. Sex-Linked Traits
1. Hemophilia
2. Red-green color blindness
B. Sex-Limited Traits
1. Genes present in both sexes of sexually reproducing species but
turned on in only one sex
2. Sex-limited genes cause the two sexes to show different phenotypes
3. These genes are responsible for sexual dimorphism

35. C. Sex-Influenced Traits
Male Female

36. VIII. Autosomal Recessive Genetic Disorders
A. Sickle Cell Anemia
B. Cystic Fibrosis
C. Tay-Sachs Disease
D. Phenylketonuria
IX. Autosomal Dominant Genetic Disorders
A. Familial Hypercholesterolemia
B. Huntington's Disease 1 in 15,000
C. Achondroplasia