Download Patterns of Heredity

11/7/2012
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1820 - French orphan Martin Fugate settled
in Troublesome Creek
Married Elizabeth Smith - 7 children of whom
4 reported to be ‘blue’
Many consanguineous marriages (normally
cousin - cousin)
One of their sons married an aunt
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6 generations later Ben Stacy born (1975)
Ben’s skin blue - no apparent cause
(1998) lips and fingernails still blue when
stressed
What is the cause? Treatment?
Madison Cawein (1960 ) proposed
answers
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1.
Certain acquired characteristics, such
as mechanical or mathematical skill,
may be inherited.
TRUE
2.
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Identical twins are always of the same
sex.
TRUE
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3.
Fraternal twins are more closely related
to each other than to other children in a
family.
3.
The father determines the sex of a child.
4.
FALSE
4.
Fraternal twins are more closely related
to each other than to other children in a
family.
TRUE
TRUE
The father determines the sex of a child.
TRUE
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5.
Each parent contributes half of a child’s
genetic make up.
TRUE
6.
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7.
Colorblindness is more common in
males than in females.
TRUE
8.
Certain drugs or alcohol can cause birth
defects in a fetus.
A person may transmit characteristics to
offspring, which he, himself does not
show.
TRUE
TRUE
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9.
Identical twins are more closely related
than fraternal twins.
TRUE
10.
Certain inherited traits may be altered
by the stars, moon, or planets early in
development
FALSE
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11.
Humans have 23 chromosomes.
12.
The tendency to produce twins may run
in families.
FALSE
TRUE
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13.
A craving for food such as strawberries
may cause a birthmark on an unborn
child.
13.
FALSE
14.
Many of a person’s inherited traits are
not apparent.
The parent with the stronger “will-power”
will contribute more to a child’s
inheritance than the other parent.
FALSE
14.
TRUE
If a person loses a limb in an accident, it is
likely that he or she will have a child with
a missing limb.
FALSE
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17.
Gregor Mendel was a monk and is
known as the “Father of Genetics”
based on his experiments with pea
plants.
19.
The total number of male births exceeds
females births each year.
TRUE
TRUE
18.
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20.
Children born to older parents usually
lack the vitality of those born to younger
parents.
FALSE
If a male mutt dog mates with a
pedigree (show quality) female dog, all
future litters of the pedigree will have
some characteristics from the mutt
male.
FALSE
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


Trait - any characteristic that can be
_____
passed from parent to offspring.
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
Alleles - two forms of a gene
________
(dominant and recessive)
_________
Heredity - passing traits from parent to
offspring
Genetics - study of heredity
__________
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

Dominant - stronger of two genes
___________
expressed in the hybrid: represented by
a capital letter (R).
Recessive - gene that shows up less
___________
often in a cross; represented by a
lowercase letter (r).


Genotype - gene combination for a
___________
trait (ex. RR, Rr, rr)
Phenotype - the physical feature
____________
resulting from ta genotype (tall, short)
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

Homozygous genotype - gene
_________________________
combination involving two dominant or
two recessive genes (ex: RR or rr): also
pure
called _______.
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

Monohybrid Cross - cross involving a
__________________
single trait
Dihybrid Cross - cross involving two traits
_______________
Heterozygous genotype - gene
_________________________
combination of one dominant and one
recessive allele (ex: Rr); also called
________.
hybrid
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
Punnett Square
________________
- used to solve
genetics
problems.
(based on
probability)
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Heredity
 __________
= the passing of traits
parents to __________.
offspring
from __________
› Transmitted by means
› of information stored
DNA
› in molecules of _______.
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Fundamentals of Genetics


heredity
Genetics = scientific study of __________
___________
Based on knowledge
that traits are
transmitted by
chromosomes
________________.
Our chromosomes
______________ are made up of
genes which are pieces of
our ________,
DNA that code for certain ______.
______
traits
› For example, both of our chromosomes
might contain the genes for hair texture or
height.
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Since
an organism receives
genes from _______
both parents it
is not exactly like either
parent but like
each parent
_______
in some ways.
Humans have
____chromosomes
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in their somatic
(body) cells.
23 chromosomes
 ____
from your mom
23 from your
and ____
dad.

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Environment =
 ____________
all the outside
forces that act on an organism.
› Affects the development, later life,
and the expression of heredity traits
of an organism.
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
WHAT MAKES YOU WHO YOU ARE TODAY?
Heredity & Environment are the
› _______________________
two great influences, acting
together all through your life.
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
Genetic messages determine what
organisms ______
may become.


The interaction of
messages and the
environment
determines what
do
organisms ______
become.

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


Gregor Mendel “Father of Genetics”
________________________
- Austrian monk
Between 1856 and 1963 his research with
garden peas
________________
led to the discovery of
heredity.
Did a statistical study of traits in garden
peas over an eight year period.
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

Organisms inherit
genetic message
____________________,
not traits!
Traits develop when
genetic messages
interact with the
environment.
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
Garden peas were a good choice for
experimentation because:
cultivated quickly
1. They can be _______________________.
2. They display ___________________
in one of
several traits
two contrasting forms:
height – tall/short
seed color – yellow/green
self-pollinating
1. They are normally ___________________
plants and are very easy to cross-pollinate.
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Mendel used logical _______________
experimental
methods and kept careful __________.
records
He used math principles of
______________
probability to interpret results
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
Mendel studied pea traits, each of
which had a dominant and a
alleles
recessive form (_______).
dominant (shows up most often)
 The ___________
gene or allele is represented with a
______________,
capital letter and the
recessive gene with a ___________
lower case of
_______________
that same letter (ex. B, b).

Mendel’s traits included:
a. seed shape – round (R)or wrinkled (r)
b. seed color – yellow (Y) or green (y)
c. pod shape – smooth (S) or wrinkled (s)
d. pod color – green (G) or white (g)
e. seed coat color – gray (G) or white (g)
f. plant height – tall (T) or short (t)
g. flower color – purple (P) or white (p)
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Mendelian Genetics Overview

The different forms or types of a
alleles
specific gene are called __________.
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Mendelian Genetics Overview

› For example, a GENE for eye color might
allele
allele
have a blue _________,
a brown _________,
allele
and a green _________.
› In plants, a gene for flower color might
have a purple allele and a white allele.
same
› If both of your parents gave us the ______
type of gene – the same allele – then
______
we are . . .
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Mendelian Genetics Overview

HOMOZYGOUS or pure (on both sets
of our chromosomes, on both sets of
genes; the allele is the ______).
same
Because our chromosomes are in
_____
two sets, we have two copies of
each gene, ______
one from our _____
mom and
one from our _____.
dad
_____
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Mendelian Genetics Overview

If one parent gave us one type of
gene and the other parent gave us a
different type, then we are . . .
› HETEROZYGOUS or hybrid – we have two
different alleles.
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Mendelian Genetics Overview

With MENDELIAN traits (the type of
traits that Mendel studied),
blend
heterozygotes DO NOT have a _______
of the two alleles.
Mendelian Genetics Overview

› Instead, one type of allele dominates –
 We show the characteristics of this allele
DOMINANT trait.
only – it is the ____________
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The other version of the trait is still
there on half of our chromosomes (so
we might still pass it on to our children,
depending on meiosis) BUT it DOES
NOT affect us right now – it is the
RECESSIVE trait.
____________
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Mendelian Genetics Overview
Whether we are heterozygous,
homozygous with the dominant trait,
or homozygous with the recessive trait
GENOTYPE (type of
it is called our ___________
genes that we have).
physically
 Which trait we _____________
show is
PHENOTYPE
our _____________ (the type of allele
that is expressed).

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Mendelian Genetics Overview

dominant allele
For example, if the __________________
of the eye color gene is brown and
the __________________
of the eye
recessive allele
color gene is blue, then the person
could have the following possibilities:
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Mendelian Genetics Overview

Two blue alleles, bb (one from ______,
mom
dad
one from _____).
homozygous
› Genotype would be ______________
recessive
___________
blue eyes
Phenotype would be ___________.
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Mendelian Genetics Overview

Two brown alleles, BB (one from mom,
one from dad).
homozygous
› Genotype would be ______________
Mendelian Genetics Overview

dominant
____________
brown eyes
Phenotype would be _____________.
Two brown alleles, Bb (one from mom,
one from dad).
heterozygous
› Genotype would be ______________
brown eyes
Phenotype would be _____________.
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Mendelian Genetics Overview
 Eye
color is actually more
complicated than that.

When only _____
one trait is being studied
in a genetic cross it is called a
_____________________.
monohybrid cross
› When parent organisms, called the
P generation are crossed, the
________________,
resulting offspring are the first filial or
F1 generation
_________________.
› When organisms of the F1 generation
are crossed, their offspring make up the
F2 generation
second filial or, _________________.
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Mendel’s Experiments
Mendel produced pure strains by
allowing plants to self-pollinate for
several generations.
 These strains were called the
__________
parental generation or P1 strain.

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Mendel’s Experiments

Mendel’s Experiments
TT x tt
P1 cross = __________
Mendel cross-pollinated two strains
and tracked each trait through two
generations. (ex. TT x tt)
Trait = plant height
› ________
Alleles = T (tall), t (short)
› ________
T
T
t
Tt
Tt
t
Tt
Tt
F1 Genotypic ratio =
100%
__________
F1 Phenotypic ratio =
100%
__________
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Mendel’s Experiments
T
T
t
Tt
Tt
t
Tt
Tt
Mendel’s Experiments
The offspring of this
cross were all
_________
hybrids showing
ONLY the
dominant trait
__________________
& were called the
First Filial or F1
__________________
generation.

Mendel then crossed two of his F1
planst and tracked their traits; know as
F1 cross
___________.
Trait = plant height
› ________
Alleles = T (tall), t (short)
› ________
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Mendel’s Experiments
Mendel’s Experiments
Tt x Tt
F1 cross = __________
T
t
T
TT
Tt
t
Tt
tt
When 2 hybrids were crossed, 75% (3/4)
of the offspring showed the dominant
trait and 25% (1/4) showed the recessive
trait.
 Two hybrids ALWAYS create a
3 (dominant trait:1(recessive trait) ratio
______________________________________.

F2 Genotypic ratio =
1 T T: 2 T t: 1 t t
___________________
F2 Phenotypic ratio =
3 tall: 1 short
___________________
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
The offspring of this cross were called the
F2 generation
__________________.
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Results of Mendel’s Experiments
factors and genes are
Inheritable ___________________
responsible for all heritable
characteristics.
Phenotype is based on ___________.
genotype
 ____________

Results of Mendel’s Experiments
Each trait
______________
is based on
two genes
_____________,
one from the mother and
the other from the father.
 True-breeding individuals are
homozygous (both alleles) are the same.
 Formulated three laws of heredity in the
early 1860’s.

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Mendel’s 3 Laws of Heredity

Law of Dominance
Law of Dominance states that when
____________________
different alleles for a characteristic are
inherited (heterozygous), the trait of only
one (the dominant one) will be
expressed. The recessive trait’s
phenotype only appears in truebreeding (homozygous) individuals.
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Mendel’s 3 Laws of Heredity


Law of Segregation states that each
____________________
genetic trait is produced by a pair of
alleles which separate (segregate)
during reproduction.
Explains the disappearance of a specific trait
in the F1 generation and its reappearance in
the F2 generation.
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Mendel’s 3 Laws of Heredity

Law of Independent Assortment states
________________________________
that each factor (gene) is distributed
(assorted) randomly and independently
of one another in the formation of
gametes (egg or sperm).
__________
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Law of Independent Assortment
Law of Independent Assortment
Explains that different traits are inherited
independently if on different
________________,
chromosomes.
 Ex: wrinkled seeds do not have to be
yellow. They can be green.


Ex. A gamete with RrYy
› R and r – separate into different gametes.
› Y and y – separate into different gamets.
› They can then recombine 4 ways to form
gametes:
RY
Ry
rY
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Inheritance of Human Traits:
Dominant/Recessive
Dark hair / Light hair
 Non-red hair / Red hair
 Curly hair / Straight hair
 Widows peak / Straight or curved hairline
 Body hair / Scant body hair
 Freckles / Normal
 Dimples / No dimples

Inheritance of Human Traits:
Dominant/Recessive
Brown eyes / Gray or blue eyes
 Normal eyesight / Nearsighted
 Large Eyes / Small eyes
 Long eyelashes / Short eyelashes
 Broad nostrils / Narrow nostrils
 Roman nose / Straight nose

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Inheritance of Human Traits:
Dominant/Recessive
Large nose / Small nose
 Free ear lobe / Attached ear lobe
 Web fingers / Normal fingers
 Bent little finger / Parallel little finger
 Left over right thumb / Right over left
thumb
ry
Inheritance of Human Traits:
Dominant/Recessive
A or B blood / O blood
 Rh+ blood / Rh- blood
 Normal clotting / Hemophilia
 Normal / Allergy
 Tongue roller / Non-roller


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Fraternal vs. Identical Twins

_______________
Identical twins develop from a _______
single
fertilized egg that splits shortly after
fertilization.
› Since they developed from the ______
same egg
they have exactly the same
___________________.
genetic makeup
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Fraternal vs. Identical Twins
Fraternal vs. Identical Twins


_______________
Fraternal twins
two
develop from ____
eggs that are
two
fertilized by _____
sperms.
By studying identical twins, geneticists
genes seem to have a
learned that _______
environment
greater influence than the ________________
on such traits as height, weight, blood pressure,
speech patterns, and gestures.
› They are completely
different people.
___________
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Fraternal vs. Identical Twins

They have also discovered that _______
genes
medical problems
play a role in some _________
once thought to be caused only by
environmental factors.
› For instance, genes can cause a susceptibility
diseases such as diabetes and certain
to __________
types of cancer.
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Inherited Diseases:
infectious diseases
___________
Infections and ___________________
CANNOT be _________.
inherited
 Certain chemical conditions of the cells
and body tissues important in resistance
against infections may be inherited.

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Inherited Diseases:

Inherited Diseases:
Diseases resulting from abnormal structure
more likely
or function of body organs are ______
to be hereditary.

Some diseases that
may be associated
with genes are:
› Diabetes
› Respiratory allergies
› Asthma
› Nearsightedness
› Farsightedness
› Night blindness
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Inherited Diseases:

Sex chromosomes determine the sex of
___________________
an individual.
XX produce a
› The X chromosomes (___)
female
________.
› An X chromosome paired with a Y
chromosome (___)
male
XY produces a ______.
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Sex Determination:
Sex-Linked Traits:

Since only a male can produce a gamete
father
bearing a Y chromosome, the ________
sex if the child.
determines the _____

NOTE: The X chromosome contains
additional genetic information that the Y
chromosome does not have, therefore a
male child actually inherits more genetic
information from his ________
mother than his father
(a very tiny amount).
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
Traits that occur ______
more frequently in one
sex than another
› Males – color blindness and hemophilia
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Sex-Linked Traits:

Occurs because other genes besides the
alleles for sex are also located on the sex
chromosomes.
recessive to the normal
are ___________
condition and the Y chromosomes appear
to lack genes for these traits.
 They

These traits generally do not show up in
females
_________.
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Punnett Squares:


Punnett Squares:
Use Punnett
Squares to solve
genetic problems!
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Practice Problems –
MONOHYBRIDS (one trait)
Practice Problems –
MONOHYBRIDS (one trait)
Black coat color in guinea pigs is
dominant over white coat color. Using a
Punnett square, show the results of
crossing a hybrid black with pure white.
Then show the results of crossing a hybrid
black and a hybrid black.
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
Black Trait – B (dominant)

White Trait – b (recessive)

Hybrid black – Bb

Pure white - bb
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Mendel’s Experiments
P1 cross =
b
B
Bb
b
Bb
Practice Problems –
MONOHYBRIDS (one trait)
Bb x bb
b
bb
Genotypes of
F1 offspring =

B (dominant)
Black Trait – _______________
2 Bb : 2 bb

b (recessive)
White Trait – _______________
bb
Phenotypes of
F1 offspring =
 Hybrid black
2 black : 2 white
(50% black : 50% white)

Bb
– __________
Bb
Hybrid black - __________
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Practice Problems –
MONOHYBRIDS (one trait)
P1 cross = __________
Bb x Bb
B
b
b Bb
bb
b Bb
bb
Now You Try Some:
1)
Genotypes of
F1 offspring =
In pigs, the white color (W) is dominant;
the black color (w) is recessive. Using
Punnett squares, show the expected
results of the following crosses.
1 BB:2 Bb:1 bb
_____________________
_
Phenotypes of
F1 offspring =
3 black : 1 white
_____________________
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1a) A pure (homozygous) white
pig is mated with a black pig.
P1 cross = _____________
WW x ww
W
W
w Ww Ww
w Ww Ww
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1b) Show a cross between two of the F1 offspring
from number 1a. Determine the genotypes and
phenotypes of the offspring in the F2 generations.
P1 cross = _____________
Ww x Ww
Genotypes of
F1 offspring =
100% Ww
_____________________
_
Phenotypes of
F1 offspring =
100% white
_____________________
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W
w
W WW Ww
w Ww ww
Genotypes of
F2 offspring =
1 WW:2Ww:1ww
_____________________
_
Phenotypes of
F2 offspring =
3 white : 1 black
_____________________
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Dihybrids (two traits)
Dihybrids (two traits)
o
Because each parent and offspring are
two traits, each one should have
using _____
4 alleles, __
2 for each _______.
trait
__
o
Each gamete produced by the P1
generations will contain 2 alleles, on for
each trait.
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DIHYBRIDS (two traits)
Dihybrid: Eye Color

Example: A plant that is heterozygous for
being tall and having green seeds is
crossed with a homozygous yellow and
short.
› Traits = seed color and plant height
› Alleles
G = green
T = tall
g = yellow
t = short
TtGg x ttgg
Cross: ______________
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TG
DIHYBRIDS (two traits)

Determine the gametes produced by
each parent by using the FOIL method.
› TtGg produces four different gametes:
_____
TG
_____
Tg
tG
_____
_____
tg
ttgg produces only one gamete:
tg
______
Phenotypes:
Tg tG
tg
tg
4 tall/green seeds
Ttgg ttGg
TtGg
4 tall/yellow
seeds ttgg
tg
4 short/green seeds
TtGg Ttgg ttGg ttgg
4 short/yellow seeds
TtGg Ttgg ttGg ttgg
Genotypes:
tg
tg4 TtGg
TtGg: 4Ttgg
Ttgg: 4 ttGg
ttGg: 4ttgg
ttgg
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Practice DIHYBRIDS (two traits)
Practice DIHYBRIDS (two traits)
In a dihybrid cross, when two traits are
considered, the number of possible
combinations of the offspring incraseas.
Suppose that black hair (B) is dominant
over blonde hair (b) and brown eyes (E)
are dominant over blue (e).
 What percent of offspring could be
expected to have blond hair and blue
eyes if:

The father has black hair (heterozygous)
and brown eyes (heterozygous) and the
mother has blonde hair and blue eyes.
BbEe
 Genotype of father = _______
bbee
 Genotype of mother = _______
 Complete the cross using the Punnett
square. Determine the percent of
offspring that will have blonde hair and
blue eyes.

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BE
be
Be bE
be blonde hair and blue eyes
be
be
111
Be bE
Practice DIHYBRIDS (two traits)
be
bbEe bbee
BbEe Bbee
25% (4/16)
BE
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Both parents have black hair
(heterozygous) and brown eyes
(heterozygous)
BbEe
 Genotype of father = _______
BbEe
 Genotype of mother = _______
 Complete the cross using the Punnett
square. Determine the percent of
offspring that will have blonde hair and
blue eyes.

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be
BE BBEE6.25%
BBEe BbEE BbEe
(1/16)
blonde BBee
hair andBbEe
blue eyes
Bbee
Be BBEe
bE
BbEE BbEE bbEE bbEe
be
BbEe Bbee bbEe bbee
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