1.What type of cross does the visual below represent? (Hint: see word wall terms) 2. How many traits are being crossed? 3. What are the genotypes of the traits being crossed? 4. What words from the word wall represent the parent genotypes?

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1.What type of cross does the visual below
represent? (Hint see word wall terms) 2.
How many traits are being crossed?3. What are
the genotypes of the traits being crossed?4.
What words from the word wall represent the
parent genotypes?
Warm-up (use pencil today)
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PART 2
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Mendels experimentation with peas continued

• Mendel performed another set of crosses in which
  he used peas that differed from each other in two
  traits rather than only one.
• A cross involving two pairs of contrasting
  traits is called a dihybrid cross (because di
  means two). example seed shape (smooth vs.
  wrinkled) and seed color (yellow vs. green).
• Mendel wanted to find out if the two traits would
  stay together in the next generation (do they
  influence one another).
• After Mendel experimented with the dihybrid
  crosses, he found that alleles sorted
  independently.
• Mendels Law of Independent Assortment
  two alleles for different traits can segregate
  independently during the formation of gametes.

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How do we use a Punnett square to conduct
Dihybrid Crosses?
We start by determining the possible gamete
combination of each parents genotype.
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The Independent Alignment of Different Pairs of
Homologous Chromosomes At Meiosis Accounts for
the Principle of Independent Assortment
Principle of Independent Assortment The
assortment of one pair of genes into gametes is
independent of the assortment of another pair of
genes.
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1. Possible Gametes To determine the number of
different gametes a parent can have, we use the
acronym FOIL (First Outer Inner Last) with
the pair of traits.
rrEe
rE
re
rE
re
There are 2 possible gametes rE and re
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2. Possible Gametes To determine the number of
different gametes a parent can have, we use the
acronym FOIL (First Outer Inner Last) with
the pair of traits.
RREe
RE
Re
RE
Re
There are 2 possible gametes Re and RE
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3. Possible Gametes To determine the number of
different gametes a parent can have, we use the
acronym FOIL (First Outer Inner Last) with
the pair of traits.
RREE
RE
RE
RE
RE
There is 1 possible gamete All gametes are RE
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Determine the different types of gametes
Hint Use the FOIL method.
Parent genotype
Number of gamete variations
TTYY

one (TY)
4.
TtYY

two (TY and tY)
5.
TtYy

6.
four (TY,Ty, tY, ty,)
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Determining Gametes
What are the different possible gametes
combinations for these parents (Rround,
rwrinkled, Ttall, tshort) ? RRTT x
RrTt
RT
RT, Rt, rT, rt
There are 4 total different gametes
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7. Determine the possible gametes and offspring
by completing the cross below (Rround,
rwrinkled, Ttall, tshort). RRTT x
RrTt
rt
rT
Rt
RT




RRTT
RrTt
RrTT
RRTt
RT
Genotypic ratio?
4 RRTT 4 RRTt 4 RrTT 4 RrTt
RT
RRTT
RRTt
RrTT
RrTt
Phenotypic ratio?
RRTT
RRTt
RrTT
RrTt
RT
16 Round/Tall
RRTT
RRTt
RT
RrTT
RrTt
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8. Determine the possible gametes and offspring
by completing the cross below (Rround,
rwrinkled, Ttall, tshort). rrTt x RRTt
Rt
RT
RT
Rt




RrTT
RrTt
RrTT
RrTt
rT
Genotypic ratio?
4 RrTT 8 RrTt 4 Rrtt
RrTt
Rrtt
Rrtt
RrTt
rt
Phenotypic ratio?
RrTT
RrTT
RrTt
RrTt
rT
12 Round/Tall 4 Round/short
rt
Rrtt
Rrtt
RrTt
RrTt
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9. Determine the possible gametes and offspring
by completing the cross below (Rround,
rwrinkled, Ttall, tshort). RrTt x RrTt
rt
rT
Rt
RT




RRTT
RrTt
RrTT
RRTt
Genotypic ratio?
RT
1 RRTT 2 RRTt 2 RrTT 4 RrTt 1 RRtt 2 Rrtt 1
rrTT 2 rrTt 1 rrtt
RRTt
RRtt
RrTt
Rrtt
Rt
rT
RrTT
RrTt
rrTT
rrTt
Phenotypic ratio?
rt
9 Round/Tall 3 Round/short 3 wrinkled/Tall 1
wrinkled/short
RrTt
Rrtt
rrTt
rrtt
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RESPONSE BOARDASSESSMENTARE YOU READY?
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Warm-up 1-10-13

• According to the table above which of the
  following
• phenotypes would probably occur in all the
  offspring
• from the parents shown above?
• Solid gray fur c. Green eyes
• Striped gray fur d. Blue eyes

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• A pea plant with the genotype TtWW is crossed
  with a pea plant with the genotype ttWw. How many
  different genotypes can be expressed in the
  offspring?
• 1
• 2
• 3
• 4

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Two cats heterozygous for short hair and tabby
striping mate. Short hair is dominant over long
hair. Tabby striping is dominant over plain
coat. 1. What is the phenotypicratio?
9 Short/Tabby 3 Short/Plain 3 long/Tabby 1
long/plain
2. What is the probability of producing a long
haired, tabby cat?
3 out of 16
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3. If you want to create a purebreed of long
haired, tabby striped cats, you would choose
kittens with which genotype(s)?
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Online Dihybrid Cross Practice
http//biology.clc.uc.edu/courses/bio105/geneprob.
htm
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Why Did Mendel Conclude That The Inheritance of
one Trait is Independent of Another?
Phenotype Ratio 9 yellow/smooth 3
yellow/wrinkled 3 green/smooth 1 green/wrinkled
Because its the only way to explain the pattern
of inheritance.
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What Works for Peas Also Works for Humans
Consider a cross between parents heterozygous for
both deafness and albinism.
This is the same 9331 ratio seen for Mendels
cross involving pea color and shape.
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Going Beyond Dominant and Recessive
There are always exceptions to the rule
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Some alleles are related through Incomplete
Dominance
WW white
a cross between organisms with two different
phenotypes produces hybrid offspring with a third
phenotype that is a blending of the parental
traits. 
Remember Incomplete Dominance
RED Flower x WHITE Flower ---gt PINK Flower
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Codominance
A.
A cross between two different phenotypes produces
a third phenotype where both traits appear
together in a hybrid offspring.
B.
A. Cross between a homozygous red flower and a
homozygous white flower.
B. Cross between homozygous IA blood type and
homozygous IB blood type.
Remember codominance
red x white ---gt red white spotted
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Codominance contd Cross between a homozygous
black horse and a homozygous white horse.
W
W
BW BW
BW BW
B
B
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Incomplete or Codominant?

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Incomplete or Codominance?
X
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Polygenic Inheritance
when a single trait is influenced by many genes
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Polygenic Inheritance
Examples Height Hair texture Skin
color eye color
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Pleiotropy When One Allele Influences Many
Traits

• Examples
• Sickle Cell Anemia
• Albinism

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Pleiotropy in Action
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Human Blood Type Inheritance Summary

• Human blood type exhibits Non-Mendelian
  inheritance
• It is inherited with multiple alleles (IA, IB, i)
• Alleles A and B are codominant (IAIB).
  Heterozygous individuals for IAIB have Type AB
  blood.

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Multiple Alleles
Many genes are present in 3 or more alleles
(versions). This is known as multiple alleles.
The human ABO blood group is determined by three
alleles (IA, IB, and i) of a single gene.
Blood Type Genotype Genotype Can Receive Blood From
A IAIA IAi AA AO A or O
B IBIB IBi BB BO B or O
AB IAIB AB A, B, AB, O
O ii OO O
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Human Blood Types
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Sex-Linked Traits

• Characteristics that are inherited from genes
  found on the sex chromosomes.

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Sex-Linked Traits

• Sex Determination
• Females XX
• Males XY
• Almost all sex-linked traits are found on the X
  chromosome
• Y chromosome contains very few genes and is
  mainly involved in sex determination

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Intro to Human a Karyotype
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Normal Male and Female Karyotypes
See page 341 in your biology textbook
In a human karyotype, the first 22 pairs of
chromosomes are the autosomes. The 23rd pair of
chromosomes are the sex chromosomes
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Examples of X-linked traits

• 1. Color Blindness
• 2. Hemophilia
• 3. Muscular Dystrophy

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Colorblindness

• A person with normal color vision sees a number
  seven in the circle above.
• Those who are color blind usually do not see any
  number at all.

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Colorblindness

• RED-GREEN COLORBLINDNESS
• People with red-green color blindness see either
  a three or nothing at all.
• Those with normal color vision see an 8.

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• Carrier person who has one recessive allele and
  one dominant allele for a trait or heterozygous
  for that trait.
• Example
• Hemophiliac carrier XHXh
• Colorblind carrier XCXc

http//webexhibits.org/causesofcolor/2.html
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Sex-linked punnett square
Question What is the probability that a carrier
female and a colorblind male will have a girl who
is colorblind (c colorblind, C normal)?
Y
Xc
XCXc XCY
XcXc XcY
XC
Xc
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Human Pedigree
See page 342-343 in your biology textbook