Download Packet 6 Genetics F16

Name __________________________________________________________ Date _____________________ Block ______
Packet 6: Genetics
Bio.3.2 Understand how the environment, and/or the interaction of alleles, influences the
expression of genetic traits.
 Bio.3.2.2 Predict offspring ratios based on a variety of inheritance patterns (including
dominance, co-dominance, incomplete dominance, multiple alleles, and sex-linked traits).
Vocabulary
o
o
o
o
o
o
o
o
o
o
o
o
o
o
Dominant
Recessive
Genotype
Phenotype
Punnett square
P1, F1 & F2 Generations
Probability
Monohybrid cross
Dihybrid cross
Test cross
Heterozygous
Homozygous
Allele
Gamete
o
o
o
o
o
o
o
o
Gene
Genetics
Heredity
Hybrid
Purebred
Punnett square
Pedigrees
Autosomal disorders
 Sickle cell
 Cystic fibrosis
 Huntington’s
disease
o Complete dominance
o Incomplete
dominance
o
o
o
o
o
o
o
o
o
o
Codominance
Multiple alleles
Polygenic traits
Sex-linked traits
Sex-linked disorders
 Colorblindness
 Hemophilia
Muscular dystrophy
Sickle cell anemia
Huntington’s disease
Cystic fibrosis
Tay-Sachs disease
PKU
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Name __________________________________________________________ Date _____________________ Block ______
MENDELIAN GENETICS
Notes: Introduction to Genetics
Word
Definition
Drawing
A segment of DNA that codes
for a protein
Alternate forms of a gene
Two alleles are the same.
Two alleles are different.
Trait that is automatically seen
even when paired with a
recessive allele.
Trait that is only seen when
two recessive alleles are
present.
Genetic make-up of an
individual.
Physical characteristic. How
you see the trait.
A box that is used to predict
the probability of offspring
when crossing two parents.

__________________ ___________________ (1822-1884) today he is considered to be
the father of modern genetics.

_____________________ is the branch of biology that studies heredity or the passing of
traits from parent to offspring.
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Name __________________________________________________________ Date _____________________ Block ______

Mendel worked with ________________ _________________. He determined 3 things
from his studies:
o For each trait an individual has _________ copies of a gene (one from each parent)
o There are alternate forms of genes called __________________________.
o There are dominant and ________________________ alleles.

Mendel’s findings led to two laws of heredity:
o _____________________________________ - 2 alleles for a trait separate during
meiosis when gametes are formed b/c homologous chromosomes and sister
chromatids separate.
o _________________________________________________ - alleles for different
traits separate independently from one another during meiosis. In other words
inheritance of one trait does not influence inheritance of another. For example if you
have blond hair you will not necessarily get blue eyes. These traits are inherited
separately.
Nature vs. Nurture:

Genes determine the physical trait, but environment can also play a role in how the trait is
expressed.
Example 1: Height and weight. Genes determine this trait, but environment can play a big role. If a
person has genes for being very tall, but does not have the proper nutrition while growing up, then
they may not be as tall as their genes would allow.
Example 2: Fur color in some animals. Genes determine fur color, but some animals have fur that
changes depending on the season. The arctic fox for instance has a white coat in the winter but a
brown coat in the summer.
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Name __________________________________________________________ Date _____________________ Block ______
Now you practice identifying the genotypes and phenotypes using the following traits and symbols.
TRAIT
DOMINANT ALLELE
RECESSIVE ALLELE
Seed shape
R = round
r = wrinkled
Seed color
Y = yellow
y = green
Seed coat color
G = gray
g = white
Flower position
A = axial
a = terminal
Plant height
T = tall
t = short
Complete the following table using the symbols and traits found above:
Trait
Genotype (symbol)
Phenotype

seed shape

RR


seed shape

Rr


seed shape

rr


plant height


tall

plant height


short

flower position


terminal

flower position


axial

seed coat color

Gg

Write the correct symbols for the following genotypes. Circle those that are not possible.
pure tall stems _______
homozygous yellow seeds _______
pure short stems _______
pure green seeds _______ homozygous terminal flowers _______ hybrid round seeds _______
pure round seeds _______ homozygous axial flowers _______
homozygous wrinkled seeds__
hybrid tall stems _______ Heterozygous wrinkled seeds _______ hybrid axial flowers _______
heterozygous short stems_______
heterozygous yellow seeds _______
heterozygous seed coat color _______
1. Why are some of these not possible? ____________________________________________
2. Can I always identify the genotype if I know the phenotype? ________________ Explain your
answer. _____________________________________________________________________
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Name __________________________________________________________ Date _____________________ Block ______
HOW TO DETERMINE IF A TRAIT CAN BE PASSED ON TO THE OFFSPRING
_____________________ is the likelihood that an event will occur.
o So if we know the genetic makeup of the mom and dad, we should be able to figure out if it is
probable and/or possible for them to pass down certain traits.
We will use a box called a _____________________ _____________________ to determine the
probability that specific traits will be passed down from parent to offspring.
_____________________ cross- a cross that involves one pair of contrasting traits.
E
(_________ Female genotype)
e
(__________ - Male genotype)
E
e
PRACTICE PROBLEM: In pea plants, tall is dominant over short. (T = tall, t = short)
1. What letters will represent a heterozygous tall plant? _______
2. What letters will represent a homozygous short plant? _______
3. What type of offspring would result if we crossed a heterozygous tall plant with a short plant? Complete
the Punnett square below to find out.
Parents (P) =
Tt X tt
a.
What are the possible
genotypes of the offspring
(include fractions)?
c.
What are the possible
phenotypes of the offspring
(include fractions)?
b.
What is the genotypic
ratio?
d.
What is the phenotypic
ratio?
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Name __________________________________________________________ Date _____________________ Block ______
Punnett Square Practice
Complete the punnett squares and questions for each of the following genetic crosses.
YOU MUST SHOW ALL WORK TO GET CREDIT!!!
1.
Red flowers are dominant to white flowers. (R = red, r = white)
a. What letters will represent a homozygous red flowered plant? ___________
b. What letters will represent a homozygous white flowered plant? ___________
c. Cross a homozygous red plant with a white plant:
d.
List the possible genotypes?
___/4 RR, ___/4 Rr, ___/4 rr
e.
What is the genotypic ratio? ____ : ____: ____
f.
What are the resulting phenotypes?
___/4 red, ___/4 white
g.
2.
What is the phenotypic ratio? ____: ____
In pea plants, round seeds are dominant to wrinkled seeds. (R=round, r=wrinkled)
a. Tell the genotype of a pea plant that is heterozygous for round seeds? _____________
b. Cross a heterozygous plant with another heterozygous plant.
c. What are the genotypes of both parents? Parent (P): ____________ X ___________
d.
List the possible genotypes? ___/4 RR, ___/4 Rr, ___/4 rr
e.
What is the genotypic ratio? ____ : ____: ____
f.
What are the resulting phenotypes?
___/4 round, ___/4 wrinkled
g.
3.
What is the phenotypic ratio? ____: ____
In pea plants, green pea pods are dominant to yellow pea pods. (G=green, g=yellow)
a. Cross a heterozygous plant with a yellow plant.
b. What are the genotypes of both parents? Parent (P):
___________ X ___________
c. What is the genotypic ratio____________________
d. What is the phenotypic ratio?________________________
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Name __________________________________________________________ Date _____________________ Block ______
Using Punnett Squares to Predict the Outcomes of Crosses
TRAIT
Pod shape
Pod color
Flower position
Plant height
DOMINANT
N = smoothALLELE
G = green
A = axial
T = tall
RECESSIVE
n = wrinkled
ALLELE
g = yellow
a = terminal
t = short
Practice problems. In order to get credit, you must SHOW ALL STEPS shown above!!!
4. Cross a plant that is heterozygous for axial flowers with a plant that has terminal flowers.
Genotypic Ratio: ______________
Phenotypic Ratio:_____________
5. Cross two plants that are both heterozygous for green pods.
Genotypic Ratio: ______________
Phenotypic Ratio:_____________
6. When a tall plant is crossed with a short plant, some of the offspring are short. What are the
genotypes of the parents and the offspring? What would be the expected phenotypic ratio of the
offspring? (Hint #1: You may need to work backwards with this problem. #2: You should have
two punnett squares drawn to prove your point).
Genotypes of Parents: ______________
Possible genotypes of offspring: ______
Phenotypic Ratio: _______________
7. Three-fourths (3/4) of the plants produced by a cross between two unknown pea plants have
axial flowers and ¼ have terminal flowers. What are the genotypes of the parent plants? SHOW
YOUR WORK!
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Name __________________________________________________________ Date _____________________ Block ______
NOTES: TEST CROSSES
A TEST CROSS is used to determine the unknown genotype of a specific organism.
o
o
In most cases, if you have an organism that is showing the ______________________
trait, you can not tell if they are homozygous or heterozygous by looking at them.
It is possible to determine their genotype by crossing (breeding) the unknown with an
individual that is homozygous _______________________. By looking at their offspring
you can usually determine the genotype of the unknown parent.
Example: In tulips, red is dominant over white. When you see a red flower you can’t be sure if
the flower is homozygous red (RR) or heterozygous red (Rr). To determine this you can
cross it with a plant that produces white (rr) flowers (homozygous recessive) & observe the
color of the offspring.
Possibility #1:
Red (R?) x white (rr)
R
r
Possibility #2:
Red (R?) x white (rr)
R
r
r
r
r
r
If some are white and some red
then the genotype must be Rr
If all of the tulips are red
then the parent must be RR.
Sample test cross: In dogs, there is a hereditary deafness caused by a recessive gene, “d.” A
kennel owner has a male dog that she wants to use for breeding purposes if possible.
 The dog can hear, so the owner knows his genotype is either DD or Dd.
 If the dog’s genotype is Dd, the owner does not wish to spend the money to use him for
breeding.
 The only way to be certain is to breed the dog with a deaf female (dd) and observe the
offspring that they produce.
1. If the male dog is DD what is the probability that he would pass on the allele for deafness? ________
2. If the male dog is Dd what is the probability that he would pass on the allele for deafness? ________
3. Since the female is dd what is the probability that she would pass on the allele for deafness?
________
Since we do not know what the genotype of the male is, we will complete both punnett
squares below to show the possible outcome of the test cross:
Assume the male is DD
Assume the male is Dd
4. If he is DD, what % of the puppies would be expected to have normal hearing? _____ deaf? ____
5. If he is Dd, what % of the puppies would be expected to have normal hearing? _____ deaf? ____
If any of the puppies are deaf, the male’s genotype MUST BE _______; but assuming a litter of at
least about 4 to 5 puppies or more, if they can all hear, his genotype is MOST LIKELY __________.
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Notes: Introduction to Dihybrid Punnett Squares
Sometimes instead of just comparing a single trait (like we have been with the four box punnett
square) – we will compare two different traits at the same time. This is called a _______________
cross.
B = Black Nose
L = Long ears
b = pink Nose
l = short ears
Use the Punnett square seen below to answer questions.
BR
Br
bR
br
BR
BBRR
BBRr
BbRR
BbRr
Br
BBRr
BBrr
BbRr
Bbrr
bR
BbRR
BbRr
X
bbRr
br
BbRr
Bbrr
bbRr
Z
Hair Color
B = Black
b = white
Hair Texture
R = rough
r = smooth
What letters would go in Box X? ___________________
What letters would go in Box Y? ___________________
What are the genotypes of the parent’s of this cross? ___________
_____________
What percent of offspring are expected to have a white coat of fur? ______________
Complex Genetics
Term
Definition
Complete
Dominance
One allele is dominant over the other.
Incomplete
Dominance
The dominant allele will not fully
cover up a recessive allele and the
trait will be a result of the two
blending or mixing together.
Codominance
Two different alleles are expressed at
the SAME time.
RR
Rr
rr
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
Practice: Incomplete Dominance
In carnations, incomplete dominance can be seen in flower color:
o red (RR)
o pink (Rr)
o white (rr)
Cross two pink carnations. Write the genotypes of the parents ______ X ______
A. Genotypic ratio: ______RR:_____Rr:______rr
B. Phenotypic ratio: ______red:_____pink:______white
C. What percent of the offspring are pink? _______
2.
In humans, hair texture is due to an incompletely dominant trait. Straight hair (H) is
incompletely dominant to curly hair (h). When crossed, they produce a heterozygous
individual with wavy hair (Hh).

Using a Punnett square, cross a curly-haired person with a wavy-haired person.
What are the genotypes of the parents?___________ X __________
A. Genotypic ratio: ______HH:_____Hh:______hh
B. Phenotypic ratio: _____straight:____wavy:______curly
C. What percent of the offspring have straight hair? _____
An example in humans of incomplete dominance:

Normal hemoglobin (no sickle cell anemia) are homozygous (HAHA)
o Their red blood cells are disk shaped, soft/flexible and live for about 120 days.

Individuals that carry the sickle cell allele are heterozygous (HAHS)
o People with this genotype have a milder form of the disease.

Individuals with sickle cell disease are homozygous (HSHS)
o Red blood cells can becomes sickle shaped, rigid and live about 20 days. They also tend to
get stuck in narrow blood vessels, which may cause complications.
Complete a punnett square to determine the chances of two sickle cell carriers having a
homozygous normal child?
Genotype of parents: ________ x ___________
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Practice: Codominance
Codominant alleles are written as capital letters with superscripts (HR). Since the trait is
inherited from both parents, it is important to still use two ‘sets of letters’ as seen
below:
The allele for red hair (HR) is codominant with the allele for white hair (HW) in cattle. Cattle that
have the genotypes HRHW are called roan because their hair is a mixture of red and white hairs.
HRHR = Red
HRHW = roan
HWHW = White
Cross a red cow and a white bull. What are the genotypes of the parents?________ X
_______
A. Genotypic ratio: ______ HRHR:_____ HRHW:______
HWHW
B. Phenotypic ratio: ______red:_____roan:______white
C. What percent of the offspring are roan? _______
In chickens, black feather color (FB) is codominant to white feather color (FW). The heterozygous
individual is a combination of black and white feathers that results in a checkered pattern (FBFW).
Cross a checkered chicken with a black chicken. What are the genotypes of the parents?___ X
____
A. Genotypic ratio: ____ FBFB:_____ FBFW:____ FWFW
B. Phenotypic ratio: __black:___checkered:___white
C. What percent of the offspring are black? ______
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Notes: Multiple Alleles
Multiple Alleles - A gene that has more than ________ alleles (or forms of a gene). In other
words, not just one dominant and one recessive allele (i.e. R and r).
The following are symbols that are used for blood types:
Blood Type
Genotype(s)
Type of Antigen
(Phenotype)
Type __
ii
1.
Type __
IA I A
or
IA i
Type __
IB IB
or
IB i
Type __
I A IB
Sample Blood Cell
A man with type O blood marries a woman with type AB blood, what are
the possible blood types of their children?
What is the probability of having a child with each of the following
blood types.
- Type A? ____________
- Type B? _________
- Type AB? ___________
2.
- Type O? ________
Is it possible for a man with type A blood and a woman with type B blood to have one child
with type O blood and another child with type AB Blood? Why or why not? Show your
work!!!
Red blood cells may also have a second antigen called ____ ________________. This trait is
complete dominance.
Phenotype
_____________________
__________________
+
+
+
Genotypes:
(Rh Rh ) or (Rh Rh )
(Rh- Rh-)
Appearance of Red
Blood Cells
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What type of blood can you get?
Blood cells have different proteins on their surface and this determines the blood type. These
proteins are called _______________. If you have A blood you produce the A antigen, people
with O blood produce NO antigen. The body’s immune system produces
___________________ (another type of protein) that recognize antigens on foreign cells and
attacks them. Antibodies and antigens match up like a lock and key. Your body produces
antibodies against antigens that YOU DO NOT HAVE. If your body produced antibodies for
antigens you have then your body would attack itself.
Blood Type
or
Phenotype
Which
Antigen is
present?
Which Antibody is
produced?
Blood you can’t
get
Blood you can
get
A
B
AB
O
Rh+
Rh Type O- is known as the ______________ ____________. Since there are no antigens on
the blood cells it can be given to any of the blood types. Even though other blood types
make antibodies, the antibodies have nothing to attach to on the O blood cells. O- can only
get from O- since they make antibodies to all other blood types.
 Type AB+ is called the ________________ ________________. A person with type AB
blood could receive a transfusion from any blood type since they don’t make antibodies to
any of them.
 Rh Factor and pregnancy – If a mom is Rh- then she makes antibodies that attack blood
cells with the Rh+ antigen. If her baby is Rh+, then the baby may be harmed. Luckily there
is an injection the mom can get to prevent her body from harming the baby.
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Notes: Polygenic Inheritance
Polygenic Traits are controlled by the interaction of more than one gene. In humans, there are
several obvious examples of polygenic traits such as hair color, eye color, height and skin tone.
Traits that are polygenic tend to show great degrees of variation.
o Skin color is caused by at least 3 different genes that code for the production of pigment.
The more dominant genes that you have, the more pigment is produced (and therefore
the darker your skin).
o If two parents have a moderate skin tone (AaBbCc), the graph below shows the
probability of having a child with each skin tone.
aabbcc
aabbCC
Lightest skin tone
AaBbCc
AABbCc AABBCC
Darkest skin tone
Notes: Sex-Linked Traits
Genes which are located on the sex chromosomes are said to be sex-______________.
 Not all genes on the sex chromosomes control gender (i.e. color-blindness and
hemophilia)
Sex-linked traits occur more frequently in _________because they have only ______ X
chromosome.
__________________ (Xn) is a very common sex-linked trait and is recessive to normal vision
(XN). More males have this disorder than females
XNXN = Normal Female
XNXn = Normal Female Carrier
XnXn = Colorblind Female
1.
XNY = Normal Male
XnY = Colorblind Male
Cross a carrier female for colorblindness with a male that is normal for
colorblindness.
A.
What are the genotypes of the parents? __________ X _____________
B.
What is the probability that one of their children will
be colorblind? _________
C.
What is the probability of a son being colorblind?
____________
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2.
Cross a normal female and a colorblind male. What is the probability that their daughter
will be a carrier?
In humans, hemophilia is a sex-linked trait located on the X chromosome. Normal blood
is dominant (XH) to hemophilia (Xh). A heterozygous female is referred to as a carrier.
1. Using a Punnett square, cross a female with hemophilia with a normal male.
___________________ X __________________
A. What percentage of this couple’s daughters will have
hemophilia? _________
B. What percentage of this couple’s sons will have hemophilia?
__________
2. Cross a carrier female with a male with hemophilia.
___________________ X __________________
A. What percentage of this couple’s sons will have hemophilia?
_______
B. What percentage of this couple’s daughters will have
hemophilia? _______
Notes: PEDIGREES & GENETIC DISORDERS
Biologists use charts called ___________________________ to study the pattern of phenotypic
inheritance in individuals and their family. When making a pedigree the following rules must be
followed:
I
II

______________ = male

______________ = female
III
IV

A ______________________ in square or circle = individual displays the trait

A ______________________ of a shaded in square or circle = individual is a carrier (may not
display the trait). This is not always known or shown.
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GENETIC DISORDERS are diseases or debilitating conditions that have a genetic basis.
When looking at pedigrees you will need to determine if the disorder is:
 Autosomal or sex-linked
 Dominant or recessive
Tips to determining this:
 If a disease is autosomal it will appear about ______________________ in males
and females.

If a disease is sex-linked it will appear in more ____________________ than
females.

If a disease is recessive than it is possible for _______________________ parents
to be normal but have a child that has the disease.

If a disease is dominant than at least ______________________ of the parents will
have the disease.
Analyze the pedigrees below and determine if the pattern of inheritance for the
disease/disorder).
Circle one in each pair:
Autosomal
or
Sex-linked
Dominant
or
Recessive
16
Circle one in each pair:
Autosomal
or
Sex-linked
Dominant
or
Recessive
Circle one in each pair:
Autosomal
or
Sex-linked
Dominant
or
Recessive
17
Autosomal Genetic Disorders:
Disorder
Huntington’s
Disease
Cystic
Fibrosis
Sickle Cell
Anemia
Tay-Sachs
Disease
Symptoms
Gradual deterioration of brain tissue
in middle age; shortened life expectancy
Mucus clogs lungs, liver and pancreas;
victims don’t survive to adulthood
Impaired blood circulation; Organ damage
Normal at birth, but deterioration of central
nervous system begins in infancy; death
occurs in early childhood
Inability of the body to break down the amino
acid phenylalanine. Failure to limit the amino
acid in the diet causes it to accumulate,
Phenylketonuria
which leads to problems w/brain
(PKU)
development, seizures and possibly mental
retardation.
Pattern of
Inheritance
Frequency among
Human births
Autosomal
Dominant
1/10,000
Autosomal
Recessive
1/2,080
(whites)
Autosomal
Recessive
1/500
(African American)
Autosomal
Recessive
1/1,600
(Jews-European
Descent)
Autosomal
Recessive
1/15,000
Caucasion and
Asians (less in
African Americans)
Sex-Linked Genetic Disorders:
Disorder
Hemophilia
Muscular
Dystrophy
Symptoms
Failure of blood to clot
Wasting away of muscles; Shortened life
expectancy
Individuals cannot distinguish between certain
Colorblindness colors (most common can’t distinguish red
from green)
Pattern of Frequency among
Inheritance
Human births
X-linked
1/7,000
Recessive
X-linked
1/10,000
Recessive
X-linked
Recessive
1/13 males
1/100 females
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