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Genetics Worksheet
Directions: Answer the following questions on a separate sheet of paper.
1. The principles of dominance, segregation and independent assortment were first
described by: a. Darwin; b. Mendel; c. Watson and Crick; d. Lamark
2. Which parental pair could produce a colorblind female? (show punnett square) a.
homozygous normal-vision mother and a colorblind father; b. colorblind mother and
normal-vision father; c. heterozygous normal-vision mother and normal-vision father; d.
heterozygous normal-vision mother and colorblind father
3. In pea plants, the trait for smooth seeds is dominant over the trait for wrinkled seeds.
When two Hybrids are crossed, which results are the most probable? (show punnett
square) a. 100% smooth seeds; b. 50%smooth and 50% wrinkled seeds; c. 75% smooth
and 25 % wrinkled seeds; d. 1005 wrinkled seeds
4. Mental retardation resulting from phenylketonuria (PKU) is caused by: a. lack of an
enzyme necessary for normal metabolism; b. overproduction of insulin; c. bacterial
infection of brain tissue; d. insufficient production of adrenaline
5. In many humans, exposing the skin so sunlight over prolonged periods of time results in
the production of more pigment by the skin cells (tanning). This change in skin color
provides evidence that: a. ultraviolet light can cause mutations; b. the inheritance of skin
color is an acquired characteristic; d. gene action can be influenced by the environment
6. When 2 four-o’clock flower plants are crossed, 48 pink flowers and 52 white flowers are
produced. The phenotypes of the parents are (show punnett square): a. pink and white;
b. pink and red; c. pink and pink; d. red and white
7. If a colorblind man marries a woman who is a carrier for color blindness, it is most
probable that: a. all of their sons will have normal color vision; b. all of their sons will be
colorblind; c. none of their children will have normal color vision; d. half of their sons
will be colorblind
8. What is the total number of chromosomes in a typical body cell of a person with Down
Syndrome? a. 22; b. 23; c. 44; d. 47
9. In humans, most sex-linked traits are due to genes that are: a. inherited only by males; b.
carried only by males; c. located on an X chromosome; d. part of an autosome
10. An organism possessing two identical alleles for a trait is said to be: a. heterozygous for
the trait; b. hybrid for he trait; c. homozygous for the trait; d. incompletely dominant for
the trait
11. Four children of the same parents each have a different blood type. What can be assumed
about the blood types of the parents (show punnett square)? a. the mother is pure
dominant and the father is hybrid; b. one parent is type O and the other is type A; c. the
mother is recessive and the father is pure dominant; d. one parent is type A and the other
is type B
NAME___________________________
Genetics Worksheet
12. Human disorders such as PKU and sickle-cell anemia, which are defects in the synthesis
of individual proteins, are most likely the result o: a. gene mutations; b. nondisjunction; c.
crossing over; d. polyploidy
13. Which term best describes most mutations? a. dominant and disadvantageous to the
organism; b. recessive and advantageous to the organism; c. dominant and advantageous
to the organism; d. recessive and disadvantageous to the organism
14. During synapsis in meiosis, portions of one chromosome may be exchanged for
corresponding portions of its homologous chromosome. This process is known as: a.
crossing-over; b. polyploidy; c. hybridization; d. nondisjunction
15. In humans, which cross will not normally produce colorblind males (show punnett
square)? a. a colorblind male and a normal female; b. a normal male and a female
carrier; c. a colorblind male and a colorblind female; d. a colorblind male and a female
carrier
16. If a trait which is not evident in the parents appears in their offspring, the parental
genotypes are most likely: a. pure recessive b. monoploid; c. homozygous; d.
heterozygous
17. A colorblind woman maries a man who is normal for color vision. What are their
chances of having a colorblind daughter? (show punnett square) a. 0%; b. 25%; c. 75%;
d. 100%
18. For a given trait; the two genes of an allelic pair are not alike. An individual possessing
this gene combination is said to be a. homozygous for that trait; b. heterozygous for that
trait; c. recessive for that trait; d. pure for that trait
19. A family has 3 boys and 1 girl. What is the chance that their next baby will be a girl?
(show punnett square) a. 25%; b. 50%; c. 75%; d. 100%
20. A student crossed wrinkled-seeded (rr) pea plants with round-seeded (RR) pear plants.
Only round seeds were produced in the resulting plants. This illustrates the principle of
(show punnett square): a. independent assortment; b. segregation; c. dominance; d.
incomplete dominance
21. A pure tall pea plant (TT) is crossed with a pure short pear plant (tt). With respect to
height, what will be the normal genotype of any resulting offspring? (show punnett
square) a. TtTt; b. TT; c. TTtt; d. Tt
22. The appearance of a recessive trait in offspring of animals most probably indicates that:
a. both parents carried at least one recessive gene for that trait; b. one parent was
homozygous recessive for that trait; c. neither parent carried a recessive gene for that
trait; d. one parent was homozygous dominant and the other parent was a hybrid for the
trait
23. Down’s Syndrome is an inherited human defect which results in mental retardation. The
most common cause of this defect is known to be: a. gene linkage; b. crossing over; c.
sex linkage; d. nondisjunction
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Genetics Worksheet
24.In humans the genes for red-green colorblindness and hemophilia are found of the: a. X
chromosomes and Y chromosomes; b. autosomes; c. Y chromosomes only; d. X
chromosomes only
25. Only red tulips result from a cross between homozygous red and homozygous white
tulips. This illustrates the principle of: a. independent assortment; b. segregation; c.
incomplete dominance; d.. dominance
26. Identical twins were separated at birth and brought together after 13 years. They vary in
height by 2 inches and in weight by 20 pounds. The most probable explanation for these
differences is that: a. they developed from 2 different zygotes; b. they differed in their
genotypes; c. their environment affected the expression of their traits; d. their cells did
not divide by mitosis
27. A man of blood type AB marries a woman of blood type A. What are the possible blood
types of their offspring if the woman’s mother was blood type O? (show punnett square)
a. A, B and O; b. AB only; c. A and B only; d. A, B and AB
28. In humans, the formation of a zygote containing three sex chromosomes (XXY) is most
likely a result of a. crossing over; b. fission; c. nondisjunction; d. independent assortment
29. In humans, sex is normally determined at fertilization by: a. 1 pair of sex chromosomes;
b. 22 pairs of autosomes; c. 2 pairs of sex chromosomes; d. 11 pairs of autosomes
30. A man heterozygous for blood type A marries a woman with blood type AB. The blood
type of their offspring could not be: (show punnett square) a. A; b. B; c. O; d. AB
31. The inheritance of ABO blood groups in humans is best explained by the fact that, of the
alleles involved, each individual must inherit: a. 4 alleles; b. 1 allele; c. 3 alleles; d. 2
alleles
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Genetics Worksheet