Heredity Chapter Problems
Mendelian Genetics
Class Work
1.
2.
3.
4.
5.
6.
7.
8.
Where do you get your traits from?
True or false: Only animal cells contain DNA.
What is the difference between the products in mitosis and meiosis?
One parent is 6’ tall. The other parent is 5’ tall. Geneticists predict that each child
they have will be exactly 5’6” tall. What hypothesis is represented here?
Define the term “phenotype.”
In Mendel’s experiments, he bred two purple flowers and ended up with some white
flowers. How do you think this happened?
How many alleles for a trait does an individual get from each parent?
Correctly label each of the allele pairs below as either “Homozygous” or
“Heterozygous”:
a. AA
b. Aa
c. aa
Homework
9. Fill in the following traits for you, your mom, and your dad:
a. Hair color
b. Eye color
c. Earlobes (attached or hanging?)
d. Hairline (widow’s peak or straight hairline?)
e. Left or right handed?
f. Can roll tongue?
g. Dimples?
h. Freckles/No freckles
10. Using the information from question #9, do you have more traits in common with
your mom or your dad? Why do you think this is?
11. How many pairs of chromosomes do humans have?
12. In order to swim better, an organism stretches its feet to make them longer. This
trait is then passed on to the offspring. What hypothesis is represented here?
13. What characteristics do scientists look for in an organism when they are preparing
for an experiment?
14. Define the term “allele.”
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7th Grade PSI
Inheritance and Variation of Traits
Using Punnett Squares
Class Work
15. Complete the sentence: Human sex cells contain ___________________ of the DNA of a
normal body cell.
16. Pat is getting dressed for school. He has 4 different pairs of sneakers he can wear
and 4 different baseball caps. If he wants to choose one of each, how many different
combinations can he make?
17. What type of letter do we use to represent a dominant trait? What type of letter is
used for a recessive trait?
18. Define the term “genotype.”
19. Does phenotype determine genotype, or is it the other way around?
20. Cats can either have a curly tail or a straight tail. Curly tails are dominant and are
represented by “T.” Using this information, write the allele pairs for each of the
following:
a. A homozygous recessive cat
b. A homozygous dominant cat
c. A heterozygous cat
21. Use question #20 to answer the following questions:
a. What kind of tail does the homozygous recessive cat have?
b. What kind of tail does the homozygous dominant cat have?
c. What kind of tail does the heterozygous cat have?
22. Set up and complete a Punnett Square that crosses a homozygous dominant
organism (AA) with a heterozygous organism (Aa).
23. Use the Punnett Square in question #22 to answer the following questions:
a. What percentage of organisms displays the dominant trait?
b. What percentage of organisms displays the recessive trait?
Homework
24. Why would geneticists use a Punnett Square?
25. Jean wants to do one page of her science workbook and one page of her spelling
workbook. There are three pages of science that she can choose from and there are
7 different spelling pages she can do. How many different combinations of
workbook pages can she make?
26. Elizabeth is designing her bedroom. She needs to pick one type of bed, one dresser,
and one chair for her room. When she went to the furniture store, she noticed that
they had 2 different types of beds, 5 different dressers, and 10 different chairs
available. How many different combinations can she make?
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7th Grade PSI
Inheritance and Variation of Traits
27. Correctly label each of the allele pairs. (“Homozygous dominant” “Homozygous
recessive” or “Heterozygous”)
a. Aa
b. AA
c. aa
28. Set up and complete a Punnett Square that crosses a homozygous recessive
organism (aa) with a heterozygous organism (Aa).
29. Use the Punnett Square in question #28 to answer the following questions:
a. What percentage of organisms displays the dominant trait?
b. What percentage of organisms displays the recessive trait?
Test Crosses
Class Work
See “Test Cross Classwork” worksheet
Homework
See “Test Cross Homework” worksheet
Genetic Mutations
Class Work
30. What are the 4 bases that make up DNA (full names and abbreviations)?
31. How do the bases always pair up?
32. What is a mutation?
33. What are three ways in which the environment can cause a mutation to happen in
your DNA?
34. Provide an example (not from our slides) of how a genetic mutation could be helpful
to an organism.
Homework
35. Where is the DNA found in the cell?
36. What makes up protein?
37. There are five different types of proteins, each with a different job. Name them and
describe each of their jobs.
38. What is the difference between an acquired mutation and a hereditary mutation?
39. Provide an example (not from our notes) of a mutation that would neither really
help nor hurt an organism.
40. What causes Down Syndrome in babies?
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7th Grade PSI
Inheritance and Variation of Traits
Answer Key
1) Organisms get their traits from their parents.
2) False
3) After mitosis, daughter cells have the same amount of DNA as the original cell. After
meiosis, the daughter cells have ½ of the DNA.
4) The blending hypothesis
5) The phenotype is the organism’s observable trait.
6) Answers will vary. (The actual answer is that each parent has 2 alleles – one is
dominant and one is recessive. This makes the parents show the dominant trait, but
carry the recessive trait.)
7) 1 from each parent
8) A) Homozygous
B) Heterozygous
C) Homozygous
9) Results will vary.
10) Answers will vary. (An accurate response would be that one parent may have passed
on more dominant traits than another.)
11) Humans have 23 pairs of chromosomes.
12) The inheritance of mutations
13) Scientists look for organisms that are small, have a short life span, are inexpensive,
produce many offspring relatively quickly, and are easy to experiment with.
14) An allele is an alternative form of a gene.
15) Human sex cells contain half of the DNA of a normal body cell.
16) 16 combinations
17) Dominant is represented by a capital letter. Recessive is represented by a lowercase
letter.
18) The genotype is what the organism’s genes, or DNA, look like.
19) Genotype determines phenotype.
20) A) aa
B) AA
C) Aa
21) A) Straight tail
B) Curly tail
C) Curly tail
22)
A
A
AA
AA
A
a
Aa
23) A) 100% dominant
B) 0% recessive trait
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Aa
trait
7th Grade PSI
Inheritance and Variation of Traits
24) A Punnett Square is a diagram that can predict the results of a genetic cross between
two individuals.
25) 21 different combinations
26) 100 different combinations
27) A) Heterozygous
B) Homozygous dominant
C) Homozygous recessive
28)
a
a
Aa
Aa
A
aa
aa
a
29) A) 50% dominant trait
B) 50% recessive trait
30) The four bases are adenine (A), thymine (T), guanine (G), and cytosine (C)
31) Adenine and thymine always pair up (A and T) and guanine and cytosine always pair
up (C and G).
32) A mutation is a change in the DNA sequence that can reshape your entire genetic code.
33) Radiation, chemicals, and viruses in the environment can cause a mutation to happen.
34) Examples will vary
35) DNA is found in the nucleus of the cell.
36) Proteins are made up of amino acids.
37) The five proteins are:
A) Antibodies – get rid of viruses and bacteria in the body
B) Enzymes - carry out the chemical reactions inside of cells and form new molecules by
reading DNA
C) Messenger proteins – send signals throughout the body
D) Proteins that give the body structure and cause it to move
E) Proteins that transport and store atoms and molecules
38) An acquired mutation happens after birth if there is an error in DNA replication or if
there is some damage from the environment. A heredity mutation occurs if the child
receives the mutated DNA from the mother or father before birth.
39) Examples will vary
40) Down Syndrome occurs when a baby is born with 3 copies of the 21st chromosome
rather than the normal 2 copies.
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7th Grade PSI
Inheritance and Variation of Traits