Genetics Classic Genetics – Mendelian Genetics Principal of genetics

1. Dominance2. The principal of independent assortment3. The principal of segregation

Examples: color of flowers – red V.S. white

dominant trait V.S. recessive traitcomplete dominance V.S. incomplete dominancegenotype V.S. phenotypehomozygous V.S. heterozygousmonohybrid V.S. dihybridgametes and zygotesPunnett square

Gregor Mendel

Reference: http://gened.emc.maricopa.edu/bio/bio181/BIOBK/BioBookgenintro.html

Crosses With Two TraitsSmooth seeds (S) are dominant over wrinkled (s)

seeds.Yellow seed color (Y) is dominant over green (y).

Human Genetics Single trait genetic inheritance –

blood type A B O Blood type A, B are dominant versus O. A and B are co-dominant.

Blood type

Phenotype Genotype Antigen Antibody

A A AA, AO A B

B B BB, BO B A

AB AB AB AB --Universal recipient

O O OO -- ABUniversal

donor

Human Genetics – Cont’dTwo traits genetic inheritance –

TONGUE ROLLING (T)TONGUE ROLLING (T) V.S. non-rolling (t)non-rolling (t)

WIDOW’S PEAK (W)WIDOW’S PEAK (W) V.S. straight hairline (w)straight hairline (w)

Parents (P): TTWW x ttww

gametes: TW tw

F1 TtWw

Heterozygous cross: TtWw x TtWw

gametes: TW Tw tW tw TW Tw tW tw

F2 ?

Punnett square – dihybrid cross

Phenotype ratio --- 9:3:3:1

TW Tw tW tw

TW TTWW TTWw TtWW TtWw

Tw TTWw TTww TtWw Ttww

tW TtWW TtWw ttWW ttWw

tw TtWw Ttww ttWw ttww

Human chromosomes All but one pair of chromosomes are the

same in both males and females. They are designated autosomes. The remaining pair of chromosomes are sex chromosomes.

Human cells have a diploid chromosome number of 46. The nucleus contains 22 pairs of autosomes and 1 pair of sex chromosomes (X and Y).

Each chromosome in this karyotype is duplicated and so consists of two sister chromatids.

Male Karyotype

Female Karyotype

Or

Sex Chromosomes XY Male XX Female

Karyotype

The photos of chromosomes are arranged in order of size and numbered.Chromosomes 23 are the sex chromosomes.

Genetic Diseases1. Tay – Sachs Disease2. Maple Syrup Urine Disease (MSUD)3. Chemochromatosis4. Cystic Fibrosis5. Colon Cancer6. Breast Cancer7. Alzheimer’s Disease8. Hemophilia9. Muscular Dystrophy10. Sickle Cell Anemia11. Fragile X Syndrome12. Turner Syndrome13. Down Syndrome14. Klinefelter Syndrome15. XXY condition16. Color Blindness

Sex Linkage

Morgan – the color of eyes in fruit fly. The sex linkage traits are usually on the

X chromosome. Sex-linked diseases:

1. Color Blindness

2. Duplchenne Muscular Dystrophy

3. Hemophilia

Color blindness genetic inheritance Muscular dystrophy genetic inheritance

Abnormal Number of Chromosomes

Eduwards Syndrome (Trisomy 18) Down’s Syndrome (Trisomy 21) Pata Syndrome (Trisomy 13) Turner Sundrome (Monosomy X) Klinefelter Syndrome (XXY) Crime Syndrome (XYY)

Trisomy 18 *

Triploid Set of Chromosomes