Semester 1, Day 9
Modes of Inheritance
Agenda

Review for Mendelian Genetics Quiz

Turn in Homework (Section 10.1)

Take Mendelian Genetics Quiz

Lecture on Modes of Inheritance
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Silent Work/Reading Time

Group Work/Reading Time
Review for Mendelian Genetics

How to determine the probability a child will be male or female

What is the definition of a dominant allele? A recessive allele?

Define genotype, phenotype, heredity, and zygosity
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What is the zygosity of the following genotypes: AA, Aa, aa?

Given a genotype (AA, Aa, aa), determine the phenotype.

Know the TITLES and DEFINITIONS of both of Mendel’s Laws

Be able to do a monohybrid Punnett square


Determine which letters to use to represent genotypes

Fill in the Punnett square correctly

Determine probabilities
Be able to do a dihybrid Punnett square
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Determine the four possible groups of alleles a person can pass on (FOIL)

Fill in the Punnett square correctly

Determine probabilities
Turn in Homework

Section 10.1



Cornell Notes
Section Assessment: #1-6
Chapter 10 Assessment

2, 3, 7, 8, 11, 12, 14, 16, 17, 20-24
Mendelian Genetics Quiz

Corrections:

#5 – Change (Fill in “orange” or “pink”) to (Fill in “red” or “purple”)

#8.d – Change ‘homozygous recessive black fur’ to ‘homozygous
recessive WHITE fur’

#8.f – Change ‘if a cat with homozygous recessive black fur mates’ to
‘if a cat with homozygous recessive WHITE fur mates’.

Reminders:

Take quiz silently

When finished, flip quiz over

Eyes on your own paper
Albinism
Modes of Inheritance

Basic Patterns of Inheritance

Mendelian Genetics




Homozygous Dominant: 2 Dominant Alleles, Shows Dominant Trait
Heterozygous: 1 Dominant Allele, 1 Recessive Allele, Shows Dom. Trait
Homozygous Recessive: 2 Recessive Alleles, Shows Recessive Trait
Recessive Genetic Disorders


Recessive allele codes for disorder
Dominant allele codes for healthy
A = normal
melanin
production
a = abnormal
melanin
production
Genotype
Zygosity
Phenotype
AA
Homozygous Dominant
Pigmented
Aa
Heterozygous
Pigmented (Carrier)
aa
Homozygous Recessive
Albino
Modes of Inheritance

Basic Patterns of Inheritance: Mendelian Genetics (cont.)
Heterozygous, carry dominant
(healthy) allele & recessive (disorder)
allele; only shows dominant trait
Example: Mom and Dad are carriers
Genotype Probabilities
A
a
AA = 1 / 4 = 25%
(homozygous dominant)
Female
Carrier!
A
AA
Aa
a
Aa
aa
Male
Aa = 2 / 4 = 50%
(heterozygous)
aa = 1 / 4 = 25%
(homozygous recessive)
Phenotype Probabilities
Pigmented (Non-Carrier) = 25%
Child
Pigmented (Carrier) = 50%
Albino = 25%
Huntington’s Disease

http://www.youtube.com/watch?v=65xf1olEpQM
Modes of Inheritance

Basic Patterns of Inheritance: Mendelian Genetics (cont.)

Dominant Genetic Disorders


Dominant allele codes for disorder
Recessive allele codes for healthy
H
h
Genotype Probabilities
AA = 0 / 4 = 0%
(homozygous dominant)
Female
Carrier!
H = Huntington’s
h = Healthy
h
h
Male
Hh
Hh
hh
Aa = 2 / 4 = 50%
(heterozygous)
aa = 2 / 4 = 50%
(homozygous recessive)
Phenotype Probabilities
hh
Huntington’s = 50%
Healthy = 50%
Child
Modes of Inheritance

Complex Patterns of Inheritance

Use uppercase
for both alleles
Incomplete Dominance

Neither allele is fully dominant over the other

Heterozygous condition BLENDS phenotypes
Example
R = red flower
W = white flower
Genotype Probabilities
Mom is a red snapdragon (RR)
Dad is a white snapdragon (WW)
W
R
R
Female
RW = 4/4 = 100%
Heterozygous
RR = 0/4 = 0%
Homozygous Dominant
RW
WW = 0/4 = 0%
Homozygous Dominant
W
Phenotype Probabilities
Pink = 100%
Male
Child
Modes of Inheritance

Complex Patterns of Inheritance (cont.)

Use uppercase
for both alleles
Codominance

Neither allele is fully dominant over the other

Heterozygous condition shows BOTH phenotypes
Example
B = Black Cat
T = Tan Cat
Genotype Probabilities
Mom is a black cat (BB)
Dad is a tan cat (TT)
B
B
Female
TB = 4/4 = 100%
Heterozygous
BB = 0/4 = 0%
Homozygous Dominant
T
TT = 0/4 = 0%
Homozygous Dominant
T
Phenotype Probabilities
Tabby (Black & Tan Stripes) = 100%
Male
Child
Modes of Inheritance

Complex Patterns of Inheritance (cont.)

Multiple Alleles

There are more than 2 allele forms for a trait

**Note: However, you still only get one allele copy from each parent for a total of 2 copies per child
Example (also shows codominance)
IA = blood type A (dominant)
IB = blood type B (dominant)
i = blood type O (recessive)
Mom is IAi (heterozygous Type A)
Dad is Ibi (heterozygous Type B)
IA
i
IB
IAIB
IBi
i
IAi
ii
Codominant
Male
Female
Child
Modes of Inheritance

Complex Modes of Inheritance: Multiple Alleles (cont.)
IA
IB
i
Male
I AI B
I Ai
i
Female
IBi
ii
Child
Genotype
Zygosity
Phenotype
Probability
IAIB
Heterozygous
Type AB
(Codominant!)
1 / 4 = 25%
IBi
Heterozygous
Type B
1 / 4 = 25%
IAi
Heterozygous
Type A
1 / 4 = 25%
ii
Homozygous
Recessive
Type O
1 / 4 = 25%
Modes of Inheritance

Complex Modes of Inheritance: Multiple Alleles (cont.)
Example #2
Mom = IAIB
Dad = IAi
IA
IA
IAIA
i
IAi
Male
IB
Female
IAIB
IBi
Child
Genotype
Zygosity
Phenotype
Probability
IAIA
Hom. Dom.
Type A
IAi
Het.
Type A
IAIB
Het.
Type AB
(codominant!)
1 / 4 = 25%
IBi
Het.
Type B
1 / 4 = 25%
2 / 4 = 50%
Modes of Inheritance

Complex Patterns of Inheritance (cont.)

Sex-Linked Traits
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Traits controlled by genes located on a sex chromosome (X-linked
traits more common)

Recall: Female (XX), Male (XY)

X-linked traits expressed in males more b/c they only have one X
chromosome

X-linked traits expressed in females less b/c the other X chromosome
usually masks (hides) the trait
Red-Green Color Blindness
Modes of Inheritance

Complex Modes of Inheritance: Sex-Linked Traits (cont.)
Example
XB = normal sight
Xb = red-green color blind
Y = Y chromosome
Mom = XBXb
Dad = XBY
XB
Genotype Probabilities
XBXB = 1 / 4 = 25%
XBXb = 1 / 4 = 25%
Xb
Female
XBY = 1 / 4 = 25%
XbY = 1 / 4 = 25%
Phenotype Probabilities
XB
Female & Healthy = 1 / 2 = 50%
X BX B X BX b
Female & Carrier = 1 / 2 = 50%
Female & Color-Blind = 0 / 2 = 50%
Y
X BY
Male & Healthy = 1 / 2 = 50%
XbY
Male & Carrier = 0 / 2 = 0%
Male & Color-Blind = 1 / 2 = 50%
Male
Child
Why can’t a male be a carrier??
Reading/Work Time

Read Chapter 12

Questions:

12.1 #1-5

12.2 #1-5

12.3 #1-5

Chapter 12 Assessment # 1-18, 20-25
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First 30 Minutes: Silent Work Time
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Remaining Time: Group Work Time (conditional)