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Figure 9.2A
100 Greatest Discoveries
Genetics
Pea Plant Variations
T.A. Knight discovery
LE 9-2b
Petal
Stamen
Carpel
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LE 9-2c
Removed stamens from purple flower
White
Carpel
Parents (P)
Purple
Transferred pollen from stamens of white flower to carpel of purple flower
Stamens
Pollinated carpel matured into pod
Planted seeds from pod
Offspring (F1)
LE 9-3a
P generation (true-breeding parents)
Purple flowers White flowers
×
All plants have purple flowers
F1 generation
F2 generation
Fertilization among F1 plants (F1 × F1)
of plants have purple flowers
3 4 of plants
have white flowers 1 4
Monohybrid�Cross
LE 9-2d
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Mendelian Theory of Heredity
Laws of Heredity
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P plants
Gametes
Genetic makeup (alleles)
All Pp F1 plants (hybrids)
F2 plants
Sperm
Phenotypic ratio 3 purple : 1 white
Gametes
PP pp
All P All p
Eggs
1 2
Genotypic ratio 1 PP : 2 Pp : 1 pp
P 1 2 p
p P
P
p
PP Pp
Pp pp
LE 9-8a
Freckles No freckles
Widow’s peak Straight hairline
Free earlobe Attached earlobe
Recessive Traits Dominant Traits
Practice Problems
1. A pea plant with green pods is crossed with a plant with yellow pods. All their offspring have green pods. a. Which allele is dominant? Which allele is recessive? b. Using letters, what is the genotype of the green parent? The
yellow parent? c. What are the genotypes of the offspring?
2. Two black mice mate. Six of their offspring are black and two are white. a. What are the genotypes of the parents? b. For which offspring are you sure of the genotypes?
LE 9-12a-a
P generation
F1 generation
Gametes
White
Pink
Red ×
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LE 9-12a-b
F2 generation
Gametes
Eggs
Sperm
1 2
Red Pink
Pink White
F1 generation
1 2
1 2
1 2
1 2
1 2
LE 9-12a P generation
F1 generation
F2 generation
Gametes
Gametes
Eggs
White rr
Pink Rr
R
R
r
r
Sperm
1 2
1 2
1 2
1 2
R 1 2
r 1 2
Red RR
Pink rR
Pink Rr
White rr
Red RR
R r
×
Rhododendron LE 9-13
Blood Group (Phenotype) Genotypes
Antibodies Present in Blood
Reaction When Blood from Groups Below Is Mixed with Antibodies from Groups at Left
O A B AB
O
A
B
AB
ii Anti-A Anti-B
Anti-B
Anti-A
IAIA or IAi
IBIB or IBi
IAIB
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Practice Problems
1. If a person of blood group AB marries one belonging to group O, what will be the blood groups of their children?
2. In four o’clock plants, the allele for red flower color is incompletely dominant to the allele for white color. If a cross between two plants produced 18 red, 32 pink, and 15 white offspring, what are the phenotypes of the parents?
3. Determine the phenotypic ratios you would expect in four o’clock plant for the following crosses: a) Red x Red b) Red x Pink c) Pink x Pink
LE 9-15
P generation
F1 generation
F2 generation
aabbcc (very light)
AABBCC (very dark)
×
×
AaBbCc AaBbCc
Sperm
Eggs
1 8
1 8
1 8
1 8
1 8
1 8
1 8
1 8
1 8
1 8
1 8
1 8
1 8
1 8
1 64
6 64
15 64
20 64
15 64
6 64
1 64
20 64
15 64
6 64
1 64
1 8
1 8
Frac
tion
of p
opul
atio
n
Skin color
At least 3 genes control skin color!
Example of: Polygenic inheritance
LE 9-22a
(male)
44 +
XY
(female)
Parents’ diploid cells
22 + X
22 + Y
22 + X
44 +
XX
Sperm Egg
Offspring (diploid)
44 +
XY
44 +
XX
Sex-linked genes
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LE 9-24b
Queen Victoria
Albert
Alice Louis
Alexandra Czar Nicholas ΙΙ of Russia
Alexis
Hemophilia in the royal family of Russia
Figure 9.24A
Red-green color blindness, X-linked trait Practice Problems
1. Two normal-visioned parents produce a color-blind son. What are the genotypes of the parents? What are the chances of their next child being color-blind daughter?
2. In fruit flies, the gene for normal eyes (B) is dominant over the allele for bar-shaped eyes (b). This trait is sex-linked. Determine the probable genotypic and phenotypic ratios expected from a cross between: a) A heterozygous female and a bar-eyed male b) A homozygous dominant female and a bar-eyed male c) A homozygous recessive female and a normal-eyed male
