Download Complex Inheritance Booklet complex_inheritance_2011

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Complex Inheritance Patterns
Dominant and Recessive Traits. So far we have examined traits that
exhibit a classic dominance and recessive pattern. In these cases, a trait is
controlled by a single gene that is either dominant or recessive. However, in
most situations it is rarely this simple. In the packet we will explore patterns
of inheritance that go ‘beyond dominant and recessive alleles’. For further
reference, be sure to read textbook pages 272-3.
Complex Inheritance Patterns
1) Codominance. Some traits show codominance, which means the
heterozygous genotype has the traits of both alleles. Since neither allele is
dominant over the other, we will use two DIFFERENT capital letters to
represent the alleles.
Here is a hypothetical example, if the allele R codes for red flowers and the
allele, W, codes for white flowers, heterozygous (RW) plants would have
flowers with red AND white spots or mottling. Note that this is different
than a blending of alleles.
Draw a picture below of each homozygous flower type and the heterozygous
flower that is codominant.
RR
WW
RW
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#1a. In a certain cattle species there are
individuals with white coats (WW), individuals with
red coats (RR), and coats that have a mixture of
red AND white hair called ‘roan’ (RW). What is the
probability that a roan cow and a roan bull would
have a white haired calf? Show all work
Roan cow: Genotype:
Gametes:
Offspring:
genotype(s)
probability
phenotype
Roan Bull
Genotype:
Gametes:
Answer to question:
#1b. In dogs, genotype BB = Black fur, while WW =White fur. However,
the heterozygous BW = Black and white splotches. What would the
probability of a puppy being black if their parents are a black and white
furred mother and black furred father?
Mom: Genotype:
Gametes:
Offspring:
genotype(s)
probability
phenotype
Dad
Genotype:
Gametes:
Answer to question:
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2) Extra Credit: Incomplete Dominance is similar to codominance, but
in incomplete dominance, the heterozygous genotype is an ‘in-between’ blending
of the two alleles. For instance, suppose there is a plant that produces red
flowers and has the genotype, RR. It crosses with a plant of the same species
that has white flowers and the genotype, WW. If this trait shows incomplete
dominance, the plants produced by this cross would have PINK flowers (a
blending of red and white).
Draw a picture below of each homozygous flower type and the heterozygous
flower that is incomplete dominant.
RR
WW
RW
#2a. Yellow coat color in guinea pigs is produced by the homozygous
genotype YY, white color by the homozygous genotype WW, and cream by
the heterozygous genotype YW. What are the genotype and phenotype
probabilities when two cream coated Guinea Pigs are mated?
Guinea Pig 1:
gametes
genotype(s)
Offspring
probability
phenotype
Guinea Pig 2
Genotype:
Gametes:
#2b. In horses, the genotype CC = a chestnut color coat, while WW = a
white colored coat. However, the heterozygous, CW = a creamy golden
coat. Also, suppose that hair length shows incomplete dominance, where
LL = long hair, SS = short hair, and LS= medium length hair. Describe the
potential coat colors and coat lengths of foals from a short-haired cream
colored mare and a medium-haired chestnut colored stud. Note: this is the
most difficult of all the problems, you will need to use a double hybrid punnett-square. Draw
and answer the question in your journal.
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3) Multiple Alleles. Sometimes a gene has more than two possible
alleles for the trait. Although, remember that each individual will only have
two alleles (one from their mother and one from their father).
Coat color in rabbits is an example of multiple alleles. Coat color is determined
by a single gene that has four different alleles (remember each rabbit will only
have 2 alleles for the gene). Tip: Please see page 273!
Allele
C
cch
ch
c
Trait
Full color
Chinchilla
Himalayan
Albino
Inheritance
Dominant to all other alleles
Dominant to ch and c alleles
Dominant to c allele
Recessive to all other alleles
#3a) Complete the chart below:
Genotype
Phenotype
_C_ _C_
Full Color
___ ___
___ ___
___ ___
___ ___
___ ___
___ ___
___ ___
___ ___
___ ___
#3b) What are the offspring possibilities and probabilities when a
heterozygous ‘Himalayan” male rabbit mates with a Chinchilla female rabbit
who ‘carries’ the albino allele? Show all work and show each step.
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4) Sex-linked inheritance. In humans there are two types of sexdetermining chromosomes. Males have an X-chromosome and a Y-chromosome
(XY). Females have TWO X-chromosomes (XX).
#4a. What type(s) of sex chromosomes can be in female eggs?
Females are ____ ____
Eggs can be:
#4b. What type(s) of sex chromosomes can be in male sperm?
Males are ____ ____
Sperm can be:
#4c. Do males or females determine the sex of their children? Explain.
The X-chromosome has many genes on it that are unrelated to determining the
sex of an individual. Color blindness is an example. Colorblindness is a
recessive trait. Females need to have BOTH copies of the allele to be
colorblind. However, males have ONLY ONE X-Chromosome. Therefore, if
they inherit the dominant allele (XN) they will have normal color vision. If they
inherit the recessive allele (Xn) they will be colorblind. This explains why
colorblindness is more common in males than females.
Male
XN Y Normal vision
Xn Y Colorblind
Female
XN XN Normal Vision
XN Xn Normal Vision
Xn Xn Colorblind
#4d. What is the possibility that a son born of a heterozygous
normal vision mother and a normal vision father will be colorblind?
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5) Polygenic Inheritance. Many human traits are the result of
polygenic inheritance, which means that one trait is determined by
two or more genes (‘poly’ = many and ‘genic’ = genes). In other words
many genes on different chromosomes determine that trait. The
phenotype will be a result of the combined action of many different
genes.
Examples of polygenic traits are human skin color and human eye color.
These traits are determined by the gene that produces and distributes
melanin. The more dominant genes present, the darker the skin or
eyes. We will use eye color as an example.
Consider eye color to be determined by 3 genes. Each contributes ‘one
unit’ of darkness:
AABBCC = very dark eyes (black)
aabbcc = very light eyes (blue)
#5a. Which of the following genotypes would have darker eyes?
AABbcc or AaBbCc? Why?
#5b. What are the possible gametes for a woman with AaBbCC as
a genotype?
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BLOOD TYPE LAB
In this lab, you will investigate the compatibility of the
different blood types. Matching blood types is crucial for blood
transfusions, which can be medically necessary after a person
has lost a large volume of blood during an accident, during
surgeries, and as treatment for certain diseases. Hundreds of
LHS staff and students (including many of you) donated during
the blood drive for just this reason - to help save lives.
If a donor’s blood type is incompatible with the recipient’s blood type,
the recipient’s immune system will produce antibodies against the
donor blood. These antibodies will cause the recipient’s blood cells to
‘agglutinate’ or clump together and may lead to death.
Review:
Your blood type is genetically determined. Human blood type is an
example of both MULTIPLE ALLELES and of CODOMINANCE.
Multiple alleles: There are 3 possible alleles in the population– IA, IB,
and i). Of course, each individual person carries only 2 alleles (one from
their mother, one from their father). The allele IA means that a
substance ‘A’ is produced which coats blood cells. The allele IB means
that a substance ‘B’ coats blood cells. The allele i means that no
coating substance is produced.
Codominance: Alleles IA and IB are both dominant over the i allele.
Alleles IA and IB are also codominant. If both alleles are present, both
substance A and substance B are produced and coat the blood cells.
Both alleles IA and IB are dominant over the i allele.
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Summary of Blood Genotypes and Phenotypes
Phenotype
Possible Genotype(s)
Type A blood
IAIA
or
IAi
Type B blood
IBIB or IBi
Type AB blood
IAIB
Type O blood
ii
INVESTIGATIVE QUESTION
In this lab we will determine which blood types are compatible, and
which blood types are incompatible?
Unfortunately, we cannot use real blood in schools, as there may be
potential for spread of blood-borne disease and illness.  Instead we
will use a model of compatibility. Each blood type will be represented
by a different color:
Type A = red
Type B = green
Type AB = brown
Type O = clear
IF blood types are compatible, they will not produce a color change (no
agglutination)
IF blood types are incompatible, they will produce a color change
(Agglutination)
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PROCEDURE
Materials:
 Sample of each type of ‘blood’ – A, B, AB, O
 Testing Tray
 Plastic Pipets
Steps:
1. Place 8 drops of type A blood in each of 4 wells on the ceramic testing tray.
These wells represent the ‘recipient’ of the blood transfusion.
2. Record the color of the recipient blood on the ‘RESULTS’ page of the
booklet.
3. Then add an equal amount of blood from each of the 4 blood types to each
well. These additions represent ‘donor blood.’
4. Record the color of each combination in appropriate circles on ‘RESULTS’
page.
5. Empty and rinse the test tray.
6. Repeat steps 1-5, this time starting with type B blood as the recipient.
7. Repeat steps 1-5, this time starting with type AB blood as the recipient.
8. Repeat steps 1-5 a final time, using type O blood as the recipient.
9. Clean up!
 Liquid from test tubes down the drain
 Rinse test trays
 Return materials
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RESULTS
Record the color of each combination below, in the appropriate circle.
DONORS
RECIPIENT
A
B
AB
O
A
B
AB
O
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DATA ANALYSIS/ CONCLUSION
1. If a person has type A blood, what type(s) of blood could they receive?
Why?
2. If a person has type B blood, what type(s) of blood could they receive?
Why?
3. If a person has type AB blood, what type(s) of blood could they receive?
Why?
4. If a person has type O blood, what type(s) of blood could you receive?
Why?
5. Which blood type is the ‘universal donor’? Why?
6. Which blood type is the ‘universal acceptor’? Why?
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7. What is your blood type? Use type A if you don’t know. Given your blood
type what are your possible genotypes?
8. What are your parent’s blood types? Use type O and type A if you don’t
know. Given their blood types, what are their possible genotypes?
9. Knowing both your AND your parent’s blood types, can you determine with
any certainty the genotypes of you and/or your parents? Why or why not?
10. Brad is heterozygous for type A blood and Angelina has type O blood.
What are the blood type possibilities and probabilities for their babies?
Show all work!
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