Genetics
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
Classic Genetics – Mendelian Genetics
Principal of genetics
1.
2.
3.

Dominance
The principal of independent assortment
The principal of segregation
Examples:
color of flowers – red V.S. white
dominant trait V.S. recessive trait
complete dominance V.S. incomplete dominance
genotype V.S. phenotype
homozygous V.S. heterozygous
monohybrid V.S. dihybrid
gametes and zygotes
Punnett square
Gregor Mendel
Reference: http://gened.emc.maricopa.edu/bio/bio181/BIOBK/BioBookgenintro.html
Crosses With Two Traits
Smooth 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
Phenotype Genotype Antigen Antibody
type
A
A
AA, AO
A
B
B
B
BB, BO
B
A
AB
AB
AB
AB
--
Universal
recipient
O
O
OO
--
AB
Universal
donor
Human Genetics – Cont’d
Two traits genetic inheritance –
TONGUE ROLLING (T) V.S. non-rolling (t)
WIDOW’S PEAK (W) V.S. straight hairline (w)
Parents (P):
gametes:
TTWW x ttww
TW
F1
tw
TtWw
Heterozygous cross:
gametes:
F2
TW
TW
TtWw x TtWw
Tw
Tw
tW
tW
?
tw
tw
Punnett square –
dihybrid cross


TW
Tw
tW
tw
TW
TTWW
TTWw
TtWW
TtWw
Tw
TTWw
TTww
TtWw
Ttww
tW
TtWW
TtWw
ttWW
ttWw
tw
TtWw
Ttww
ttWw
ttww
Phenotype ratio --- 9:3:3:1
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
Karyotype
The photos of chromosomes
are arranged in order of size
and numbered.
Chromosomes 23 are the sex
chromosomes.
Sex Chromosomes
XY Male
XX Female
Or
Genetic Diseases
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
Tay – Sachs Disease
Maple Syrup Urine Disease (MSUD)
Chemochromatosis
Cystic Fibrosis
Colon Cancer
Breast Cancer
Alzheimer’s Disease
Hemophilia
Muscular Dystrophy
Sickle Cell Anemia
Fragile X Syndrome
Turner Syndrome
Down Syndrome
Klinefelter Syndrome
XXY condition
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.
2.
3.


Color Blindness
Duplchenne Muscular Dystrophy
Hemophilia
Color blindness genetic inheritance
Muscular dystrophy genetic inheritance
Abnormal Number of
Chromosomes
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Eduwards Syndrome (Trisomy 18)
Down’s Syndrome (Trisomy 21)
Pata Syndrome (Trisomy 13)
Turner Sundrome (Monosomy X)
Klinefelter Syndrome (XXY)
Crime Syndrome (XYY)
Triploid Set of Chromosomes
Trisomy 18 *