What I need to know about Mendelian Genetics
Differentiate between heterozygous and homozygous genotypes
by using letter symbols.
1. Indicate which is heterozygous by writing He and which is homozygous by writing Ho.
Aa ____
LL ____
Nn ____
CC ____
MM ____
ee ____
ff ____
Gg ____
Pp ____
Ss ____
WW ____
ww ____
Tt ____
tt ____
aa ____
Zz ____
2. Use the following terms to fill in the blanks:
Homozygous Dominant, Homozygous Recessive, Heterozygous
a. The genotype RR indicates a trait that is _______________.
b. The genotype Tt indicates a trait that is ________________.
c. The genotype ee indicates a trait that is _______________.
3. A student was describing the height, color, and type of plants that Mendel used in his experiment
regarding genetics. Was the student describing the phenotypes or the genotypes of the plants?
_________________________
4. A tall is dominant to short plant.
Write the phenotype for the following genotypes.
a. TT__________
b. Tt ___________
c. tt___________
Explain the law of dominance.
5. If a trait is expressed, it is said to be dominant/recessive. (circle one)
6. If a trait is hidden or unexpressed it is said to be dominant/recessive. (circle one)
Predict how genes sort and recombine to produce variations in
offspring using Punnett squares.
7. In aliens, green in dominant over orange. Cross a homozygous dominant green alien with a
heterozygous green alien.
Phenotypic ratio: ________________
Genotypic ratio: ____________________
What percentage of the aliens born will be orange? ____________
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8. Pink polka dots are dominant to blue polka dots. Cross a recessive polka-dotted elephant with a
heterozygous polka-dotted elephant.
Phenotypic ratio: _______________
Genotypic ratio: ________________
What percentage of the elephant born will be
heterozygous?__________
9. A group of students wanted to determine how mouse fur color is passed from one generation to
the next. The students mated mice for one year and recorded their results in the table.
Parent Group
Children of Each Parent Group
Percent Black
Percent White
Both Black Mice
85
15
One Black Parent,
One White Mouse
62
38
Both White Mice
0
100
Based on the data, is black or white fur color dominant? _____________________ Why?
________________________________________________________________________________
________________________________________________________________________________
How can two black mice create a white mouse?
________________________________________________________________________________
Show the punnett square for proof:
10. Multiple Choice: A litter of puppies is 12 dogs. Six puppies are white and six puppies are brown.
In puppies the allele for brown in dominant to the allele for white. What would the parent’s
genotype be for this litter? (show the punnett square)
A. rr x Rr
B. Rr x Rr
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Explain why recessive traits are more often expressed in the male.
11. The allele for muscular dystrophy is recessive. A female with the genotype, XdXd marries a man
with the genotype XDY.
What is the likelihood that their children will have muscular
dystrophy?
12. Hemophilia is a sex linked trait. A female carrier marries a man that is does not have hemophilia.
What percentage of their offspring will inherit the trait for hemophilia?
____________
What percentage of their offspring will NOT inherit the gene for
hemophilia? __________
What percentage of the males will inherit the trait for hemophilia?
_____________
What percentage of the females will be carriers?_____________
13. Fill in the blanks with the following terms:
Allele, recessive, X, males, hemophilia, carrier, female, affected, X chromosome, X AXa, XaY
Sex-linked traits are found on the _____________________________________. Typically they are
most often expressed in ________ because they have only one ___ chromosome. A ________ can
be affected; however, it is rare. Some of the time, a female can be a __________, which means that
she has one ________ for the trait, but does not show it. A male cannot be a carrier and can only be
normal or __________. Two conditions that are sex linked are _______________ and
colorblindness. The genotype of a female carrier would be _______. The genotype of a male who is
affected would look like this _____.
Illustrate and explain how expressed traits are passed
from parent to offspring by analyzing pedigree charts.
14. What does a pedigree chart show?
______________________________________________
____________________________________________
15. The pedigree to the right shows a (sex linked
trait/normal trait). (circle one) Explain how you know.
____________________________________________
____________________________________________
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16. Shade in all the heterozygous
individuals in this pedigree.
17. Using the pedigrees, draw symbols for the meanings listed:
Symbol
Meaning
Affected Female
Normal Male
Carrier Female
Affected Male
Explain what the roman numerals represent.
________________________________________________________________________________
_______________________________________________________________________________
Explain how the marriage of two people is shown.
________________________________________________________________________________
________________________________________________________________________________
Explain how offspring are shown.
________________________________________________________________________________
_______________________________________________________________________________
The pedigree below shows the occurrence of red-green colorblindness in four generations of
a family.
Use the information in the pedigree to answer the following
questions:
18. How many individuals have red-green colorblindness in
the four generations shown in the pedigree?
a. 3
b. 4
c. 7
d. 12
19. In generation IV, individual 5 married someone who is not a carrier of redgreen colorblindness. If they have a female child, what is the chance that she
will be born with red-green colorblindness?
a.
0%
b.
25%
c.
50%
d.
100%
20. How many females are carriers for red-green colorblindness? ________
21. How do you know that this pedigree is a sex-linked trait?
______________________________________________________________________________
______________________________________________________________________________
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