Name: 
 

Genetics, Heredity Practice Test



Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
 

1. 

Factors that control traits are called
a.
genes.
b.
purebreds.
c.
recessives.
d.
parents.
 

2. 

Scientists call an organism that has two different alleles for a trait a
a.
hybrid.
b.
trait.
c.
purebred.
d.
factor.
 

3. 

What does the notation TT mean to geneticists?
a.
two dominant alleles
b.
two recessive alleles
c.
at least one dominant allele
d.
one dominant and one recessive allelle
 

4. 

What does the notation Tt mean to geneticists?
a.
two dominant alleles
b.
two recessive alleles
c.
at least one recessive allele
d.
one dominant allele and one recessive allelle
 

5. 

What is probability?
a.
the actual results from a series of events
b.
the likelihood that a particular event will occur
c.
the way the results of one event affect the next event
d.
the number of times a coin lands heads up
 

6. 

What does a Punnett square show?
a.
all the possible outcomes of a genetic cross
b.
only the dominant alleles in a genetic cross
c.
only the recessive alleles in a genetic cross
d.
all of Mendel’s discoveries about genetic crosses
 

7. 

If a homozygous black guinea pig (BB) is crossed with a homozygous white guinea pig (bb), what is the probability that an offspring will have black fur?
a.
25 percent
b.
50 percent
c.
75 percent
d.
100 percent
 

8. 

An organism’s physical appearance is its
a.
genotype.
b.
phenotype.
c.
codominance.
d.
heterozygous.
 

9. 

What does codominance mean in genetics?
a.
Both alleles are dominant.
b.
Both alleles are recessive.
c.
The alleles are neither dominant nor recessive.
d.
Each allele is both dominant and recessive.
 

10. 

What happens during meiosis?
a.
Each sex cell loses half of its chromosomes.
b.
Chromosome pairs separate to form new sex cells.
c.
Each sex cell copies itself to form four new chromosomes.
d.
Chromosome pairs remain together when new sex cells are formed.
 

11. 

When sex cells combine to produce offspring, each sex cell will contribute
a.
one fourth of the normal number of chromosomes.
b.
half the normal number of chromosomes.
c.
the normal number of chromosomes.
d.
twice the normal number of chromosomes.
 

12. 

What is a mutation?
a.
any change that is harmful to an organism
b.
any change in a gene or chromosome
c.
any change that is helpful to an organism
d.
any change in the phenotype of a cell
 

13. 

Which term refers to physical characteristics that are studied in genetics?
a.
traits
b.
offspring
c.
generations
d.
hybrids
 

14. 

The different forms of a gene are called
a.
alleles.
b.
factors.
c.
masks.
d.
traits.
 

15. 

Where does protein synthesis take place?
a.
in the ribosomes in the nucleus of the cell
b.
on the ribosomes in the cytoplasm of the cell
c.
in the chromosomes in the nucleus of the cell
d.
on the chromosomes in the cytoplasm of the cell
 

16. 

What does the notation tt mean to geneticists?
a.
two dominant alleles
b.
two recessive alleles
c.
at least one dominant allele
d.
one dominant and one recessive allelle
 

17. 

An organism’s genotype is its
a.
genetic makeup
b.
feather color
c.
physical appearance
d.
stem height
 

18. 

Which nitrogen base in RNA is NOT part of DNA?
a.
adenine
b.
guanine
c.
cytosine
d.
uracil
 

19. 

An organism that has two identical alleles for a trait is
a.
codominant.
b.
tall.
c.
homozygous.
d.
heterozygous.
 

20. 

A heterozygous organism has
a.
three different alleles for a trait.
b.
two identical alleles for a trait.
c.
only one allele for a trait.
d.
two different alleles for a trait.
 

21. 

Which of these traits is controlled by a gene with multiple alleles?
a.
straight hairline
b.
smile dimples
c.
widow’s peak
d.
blood type
 

22. 

Which combination of sex chromosomes results in a male human being?
a.
XX
b.
YY
c.
XY
d.
either XX or YY
 

23. 

Why are sex-linked traits more common in males than in females?
a.
All alleles on the X chromosome are dominant.
b.
All alleles on the Y chromosome are recessive.
c.
A recessive allele on the X chromosome will always produce the trait in a male.
d.
Any allele on the Y chromosome will be codominant with the matching allele on the X chromosome.
 

24. 

How does a geneticist use pedigrees?
a.
to create genetic crosses
b.
to replicate identical strings of DNA
c.
to prove that sex-linked traits are caused by codominant alleles
d.
to trace the inheritance of traits over generations of families
 

25. 

What is a pedigree?
a.
a chart that tracks which members of a family have a particular trait
b.
a geneticist who studies the inheritance of traits in humans
c.
a picture of all of the chromosomes in a cell
d.
an allele passed from parent to child on a sex chromosome
 

26. 

Genetic disorders are caused by
a.
pedigrees.
b.
mutations.
c.
dominant alleles.
d.
sickle-shaped cells.
 

27. 

Which genetic disorder causes the body to produce unusually thick mucus in the lungs and intestines?
a.
hemophilia
b.
Down syndrome
c.
cystic fibrosis
d.
sickle-cell disease
 

28. 

Cloning results in two organisms that are
a.
both adult mammals.
b.
produced from cuttings.
c.
genetically similar.
d.
genetically identical.
 

29. 

Which of these is an example of the benefits of genetic engineering?
a.
cross-breeding to create disease-resistant crops
b.
creating human insulin to treat people with diabetes
c.
analyzing karyotypes and pedigree charts
d.
growing a new plant from a cutting
 

30. 

No two people have the same DNA, except for
a.
crime suspects.
b.
brothers.
c.
sisters.
d.
identical twins.
 

31. 

Sex-linked genes are genes on
a.
the X chromosome only.
b.
the Y chromosome only.
c.
the X and Y chromosomes.
d.
all 23 pairs of chromosomes.
 

32. 

A carrier is a person who has
a.
one recessive and one dominant allele for a trait.
b.
two recessive alleles for a trait.
c.
two dominant alleles for a trait.
d.
more than two alleles for a trait.
 

Short Answer
 
 
Use the diagram to answer each question.

genetics_practice_files/i0350000.jpg
 

33. 

Which trait - white flowers or purple flowers - is controlled by a dominant allele? Which is controlled by a recessive allele? How do you know?
 

34. 

In which generation are the parents purebred? In which generation are they hybrids?
 

35. 

In the F1 generation, what is the genotype of the offspring? What is their phenotype?
 
 
Use the diagram to answer each question.

genetics_practice_files/i0390000.jpg
 

36. 

What do the circles in the pedigree represent? What do the squares represent?
 

37. 

Which pairs of individuals in the pedigree have children?
 

38. 

Which individuals have the trait that is traced by the pedigree?
 

39. 

Which individuals are carriers of the trait that is traced by the pedigree?
 

Essay
 

40. 

In pea plants, the allele for smooth pods (S) is dominant over the allele for pinched pods (s). Construct a Punnett square that shows a cross between an SS plant and an Ss plant. Predict what percent of the offspring are likely to have smooth pods.
 

41. 

Is it possible for a son to inherit an allele on an X chromosome from his father? Explain why or why not.
 



 
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