Download Trait Dominant Allele Recessive Allele Trait How it is inherited Pod

Unit 9: Genetics and Inheritance
Study Sheet
DIRECTIONS: This worksheet is a guide for your studying and represents what your Biology
teachers expect you to have learned and be able to do by the end of this unit.
Key Terms:
Genotype
Phenotype
Allele
Trait
Punnett square
X-linked/sex-linked
Gamete
Dominant trait
Recessive trait
Co-dominant traits
Incompletely dominant
traits
Pedigree
Offspring
Heredity
Genetics
Heterozygous
Homozygous
Autosomal
Karyotype
Background Information:
Use the following information to assist with practice problems. Traits are completely dominant unless otherwise noted.
Trait
Pod Shape
Pod Color
Plant Height
Dominant Allele
Smooth (N)
Green (G)
Tall (T)
Recessive Allele
Wrinkled (n)
Yellow (g)
Short (t)
Trait
Hemophilia (h)
Colorblindness (b)
Essential Question: Can two brown-eyed parents have a blue-eyed child?
Learning Target
You should be able to …
A. Describe how a recessive trait can be expressed in an individual’s phenotype.
1. What is the difference between a dominant and a recessive allele? How was
this expressed in our furball genetics lab?
2. Why are men more likely to have recessive sex-linked traits?
B. Describe how alleles for specific traits are inherited from parents.
1. What is the difference between a genotype and a phenotype?
2. How many alleles does each zygote contain for each gene? Where do these
come from?
C. Explain how the work of Gregor Mendel contributes to our knowledge of
heredity and genetics.
1. Explain the law of independent assortment. How was it represented in our
“Mendel’s Laws at Work” lab?
2. Explain the law of segregation of alleles. How was it represented in our
“Mendel’s Laws at Work” lab?
3. Two plants are crossed. 76 of their offspring are tall and 22 are short. What
are the most likely genotypes of the parent plants for the height gene?
Explain how this relates to Mendel’s studies.
4. Some traits appear more frequently together, for example, blond hair and
blue eyes are two different traits, coded for by at least 2 different genes,
but are often inherited together. What law of Mendel’s does this violate?
Why? What could explain this observation?
How it is inherited
Recessive, on X chromosome
Recessive, on X chromosome
Know the
answer?
Know where
to find the
answer?
D. Construct and explain what a Punnett Square represents (use the alleles above!)
1. What is the phenotype of a plant with the genotype Nn?
2. What is the genotype of a plant that is short?
3. Cross a plant heterozygous for green pod color with a yellow pod color
plant. Give the genotypic and phenotypic ratios of the offspring as a
percentage.
4. A plant with wrinkled pods is crossed with a plant that is homozygous for
smooth pods. Give the genotypic and phenotypic ratios of the offspring as a
fraction.
5. What do the letters at the top and sides of the Punnett Squares represent?
6. What do the letters in the center of the Punnett Square represent?
E. Construct and explain what a dihybrid cross represents.
1. What is meant by a “dihybrid” cross?
2. A plant with wrinkled pods is crossed with a plant that is homozygous for
smooth pods. Give the genotypic and phenotypic ratios of the offspring as a
fraction
3. Cross a pea plant that is wrinkled and yellow with a pea plant that is
heterozygous for pod shape and pod color. What percentage of their
offspring is expected to be smooth and green?
4. Cross a pea plant that is heterozygous for height and yellow with a plant
that is homozygous dominant for height and heterozygous for pod color.
Give the phenotypic ratio of the offspring in the colon or fraction form.
H. Identify and explain inheritance patterns associated with exceptions to
complete dominance.
1. What is the difference between incomplete dominance and codominance?
Give a unique example (one we haven’t studied in class!) to demonstrate
your understanding.
2. If fur color in cats is incompletely dominant, what is the phenotype of a cat
with a black and white allele?
3. If fur color in cats is co-dominant, what is the phenotype of a cat with a
black and white allele?
4. Barbara has B blood type. Alan has A blood type. What are the possible
blood types of their children? (HINT: You will need to make more than one
Punnett square.)
5. Mark has blood type O. His wife has AB blood. Give the genotypic ratios of
their children in fractions.
I. Construct and interpret a pedigree for family transmission of a specific heritable
trait. Use the Pedigree shown below to answer the following questions.
1. What does a Pedigree show? How are pedigrees constructed?
2. How are males and females represented in a pedigree?
3. How are “affected” individuals and “unaffected” individuals
represented in a pedigree?
4. How does a pedigree indicate that an individual is deceased?
5. Is this trait dominant or recessive?
6. What are the possible genotypes of the individuals that have shaded
shapes?
7. What are the possible genotypes of the individuals that have shapes
that are not filled in?
J. Explain how traits inherited on sex chromosomes are inherited differently from
traits found on autosomes.
1. A boy has hemophilia (a sex-linked trait). From which parent did he receive
the hemophilia trait? Does this parent also have hemophilia? Explain how
you know.
2. A woman who has hemophilia marries a man who does not have
hemophilia.
a. Genotype of a woman who has hemophilia
b. Genotype of a man who does not have hemophilia
c. What fraction of their children is expected to be a son with
hemophilia?
d. What fraction of their children is expected to be a daughter without
hemophilia?
e. What percentage of sons is expected to have hemophilia?
f. What percentage of daughters is expected to not have hemophilia?
3. Sally who is not colorblind has a father who is colorblind. She marries Tom
who is not colorblind.
a. Sally’s genotype
b. Tom’s genotype
c. What percentage of sons is expected to be colorblind?
d. What percentage of daughters is expected to be colorblind?
H. Describe the impact of mistakes during cellular division.
1. What is prenatal testing? What are doctors trying to obtain during prenatal
testing?
2. What is a karyotype? How do scientists create a karyotype?
3. When reading a karyotype, how can you tell if:
a. It is from a man or a woman?
b. The individual has a chromosomal disorder?
4. What causes chromosomal disorders?
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