Genetics Unit Review Sheet
Column A
Column B
1. the passing of traits from parents to offspring - h
a. egg
2. an organism with the same alleles for a trait - J
b. genetics
3. factors that control traits - t
c. recessive
4. physical characteristics of organisms - p
D. sperm
5. an allele whose trait always shows up in the organism - m
e. zygote
6. the different forms of a gene - r
f. Punnett Square
7. the scientific study of heredity - b
g. sex-linked
8. an allele whose trait is masked in the presence of a dominant allele - c
h. heredity
9. alleles passed from parent to child on a sex chromosome. - g
i. meiosis
10. Three or more forms of a gene that code for a single trait are called - n
j. homozygous
11. one recessive allele for a trait and one dominant allele for the same trait - w
k. pedigree
12. chart that tracks which members of a family - k
l. dominant
13. fertilized egg – e
m. codominance
14. male gamete - d
n. multiple alleles
15. female gamete - a
o. probability
16. Fertilized egg that has undergone up to 8 weeks of development q
p. phenotype
17. process by which sex cells are created - i
q. embryo
18. known as the father of genetics - u
r. alleles
19. composed of DNA - m
s. chromosome
20. the likelihood that a particular event will occur - o
t. genes
21. an organism’s genetic makeup, or allele combinations - v
u. Gregor Mendel
22. inheritance pattern in which the alleles are neither dominant nor recessive - m
v. genotype
23. a chart that shows all the possible combinations of alleles that can result from a
genetic cross - f
w. heterozygous
Which type of reproduction produces a greater variation among offspring?
a. Both sexual and asexual reproduction
b. Neither sexual or asexual reproduction
c. Asexual reproduction
d. Sexual reproduction
What is the reason that a trait like eye color in humans tends to run in families?
a. Eye color is an environmental trait
b. Eye color is a genetic trait
c. Eye color is a chemical trait
d. Eye color occurs by chance
Alexa has blue eyes. What is her genotype? B - brown, b - blue
Mother
Father
BB
Bb
Bb
bb
a. BB
b. bb
c. Bb
d. Not enough information
Alexa’s brother, Matt, has brown eyes. Which statement best describes one way that Matt could have gotten brown
eyes: (B - brown, b - blue)
Mother
Father
BB
Bb
Bb
bb
a. Matt was born with blue eyes, but they turned brown as he got older
b. Matt received a brown-eyed gene from at least one parent.
c. Matt received both eye color genes from both parents
d. Matt’s eye color came from his father
Adam cut his hand and the damaged cells need to be replaced. Mitosis is the cell division process that will replace the
damaged cells with new cells. What statement best describes the genetic makeup of the new cells?
a. They contain the same genetic information as the damaged cells
b. The contain genetic information that is different from the damaged cells.
c. The contain no genetic information
d. They contain a bacterial infection that will form the new cells
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What do the circles in the pedigree represent? Females
What do the squares represent? Males
Which pairs of individuals in the pedigree have children? A&B, C&D, F&G, H&I
Which individuals have the trait that is traced by the pedigree? F&J
Which individuals are carriers of the trait that is traced by the pedigree? A,C,N,O
Could the trait that is traced by this pedigree be sex-linked? Explain why or why not. Yes. There is a
higher incidence in males than in females.
Genetics Unit Assessment Review Sheet #2
Essay Questions. Please write answers on a separate piece of paper.
 In pea plants, green pod color is controlled by a dominant allele. Yellow is controlled by a recessive
allele. Explain why a plant with yellow pods can never be a hybrid. Because the recessive allele would
be masked if it were a heterozygote.
 A woman gives birth to a son. Two years later, she gives birth to another son. What is the probability
that her third child will be a girl? Explain your reasoning. ½. Each event is independent of the others.
 Human skin comes in a range of colors ranging from light to very dark. Explain why skin color is not
likely to be controlled by a single gene. Because it is a range, you would expect many alleles to control
the gene. Polygenic Inheritance.
 Is it possible for a son to inherit an allele on an X chromosome from his father? NO Explain why or why
not. There is no other way for a son to get the y chromosome excepts from his father, and his father
can only donate one sex chromosome.
 Explain how you can tell the sex of a person by looking at that person’s karyotype (chromosomal
structure). Two x chromosomes are the same size and banding pattern. The x and the Y would be
different.
 A person with blood type AB has the alleles IA and IB. A person with blood type O has the alleles ii. Is it
possible for a person with blood type AB to have a child with blood type O? Explain why or why not.
No. The AB person must donate a dominant allele. That person cannot donate a recessive allele to
make a homozygous recessive.
 Why is sexual reproduction an evolutionary advantage? It allows for greater variation. Variation is
good if the environment changes.
SIMPLE DOMINANT & RECESSIVE TRAITS
Let's say that in seals, the gene for the length of the whiskers has two alleles. The dominant allele (W)
codes long whiskers & the recessive allele (w) codes for short whiskers.
What percentage of offspring would be expected to have short whiskers from the cross of two long-whiskered
seals, one parent is homozygous dominant and the other one is heterozygous?
All offspring would be dominant, WW or Ww
 If one parent seal is pure long-whiskered and the other is short-whiskered, what percent of offspring
would have short whiskers?
None. They would all be Ww
In dogs, there is a hereditary deafness caused by a recessive gene, “d.” A kennel owner has a male dog that
she wants to use for breeding purposes if possible. The dog can hear, so the owner knows his genotype is
either DD or Dd. If the dog’s genotype is Dd, the owner does not wish to use him for breeding so that the
deafness gene will not be passed on. This can be tested by breeding the dog to a deaf female (dd).
 Draw the Punnett squares to illustrate these two possible crosses. In each case, what percentage/how
many of the offspring would be expected to be hearing? Deaf?
DD x dd – All offspring are dominant phenotype. (Dd)
Dd x dd – ½ offspring are dominant phenotype, ½ are recessive phenotype (Dd/dd)
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How could you tell the genotype of this male dog?
If all offspring are not deaf, then the dog is DD
If half the offspring are deaf, then the dog is Dd
 Also, using Punnett square(s), show how two hearing dogs could produce deaf offspring.
Dd x Dd – ¼ of the offspring will be dd and deaf.
In humans, brown eyes (B) are dominant over blue (b). A brown-eyed man marries a blue-eyed woman and
they have three children, two of whom are brown-eyed and one of whom is blue-eyed.
 Draw the Punnett square that illustrates this marriage.
Bb x bb – 3 brown, 1 blue
 What is the man’s genotype? Bb
 What are the genotypes of the children? BB or Bb (brown) and bb (blue)
CODOMINANT TRAITS
In humans, wavy hair (CS) results by the co-dominant situation of curly hair (C) and straight hair (S).
 What are the possible results if a curly-haired man and wavy-haired woman have children?
CC x CS – ½ curly, ½ wavy
Cattle can be red (RR = all red hairs), white (WW = all white hairs), or roan (RW = red & white hairs
together).
 Predict the phenotypic ratios of offspring when a homozygous white cow is crossed with a roan bull.
RW x WW – ½ white, and ½ roan
 What should the genotypes & phenotypes for parent cattle be if a farmer wanted only cattle with red
fur?
RR x RR
INCOMPLETE DOMINANCE
A cross between a blue blahblah bird (I made this bird up) & a white blahblah bird produces offspring that
are silver. The color of blahblah birds is determined by just two alleles.
 What are the genotypes of the parent blahblah birds in the original cross?
BB x WW
 What is/are the genotype(s) of the silver offspring?
BW
 What would be the phenotypic ratios of offspring produced by two silver blahblah birds?
1 BB, 2 BW, 1WW
The color of fruit for plant "X" is determined by two alleles. When two plants with orange fruits are crossed
the following phenotypic ratios are present in the offspring: 25% red fruit, 50% orange fruit, 25% yellow
fruit.
 What are the genotypes of the parent orange-fruited plants?
RY
Multiple alleles
 Could a man with type B blood and a woman with type AB produce a child with type O blood?
NO
A man with Type A blood marries a woman with type B blood. Their child has type O blood.
 What are the genotypes for these individuals?
IAi & IBi
 What other genotypes, and in what frequencies, would you expect to find in offspring produced from
this marriage?
1 IAIB, 1 IAi, 1 IBi, & 1 ii
A woman with Type O blood and a man who is Type AB have are expecting a child.
 What are the possible blood types of the kid?
A or B
 What are the possible blood types of a child whose parents are both heterozygous for "B" blood type?
B or O
 Determine the possible genotypes & phenotypes with respect to blood type for a couple who's blood
types are homozygous A & heterozygous B.
2 IAIB, 2 IAi. ½ AB, ½ A
SEX-LINKED
Hemophilia is a recessive trait located on the X chromosome.
A woman who is a carrier for hemophilia marries a hemophiliac man. What are the phenotypes of their
children? How would you council this couple if they are considering having children?
XHXh x XhY
½ of their children would be hemophiliac. 1 of every 2 females and 1 of every 2 males would have
hemophilia.
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On your first day interning in the office of a human geneticist, a man with purple ears walks in. You
questioned the man and wrote down the following family history.
The man's mother and one of his sisters also had purple ears, but his father, his brother, and two other
sisters had normal ears. The man and his normal-eared wife had seven children, including four boys
and three girls. Two girls and two boys had purple ears.
Draw the family pedigree and indicate what form of inheritance that the purple-ear trait most likely
follows.
This is a simple recessive trait.
a. Could this trait be inherited as a simple autosomal recessive?
b. Could this trait be inherited as a simple autosomal dominant?
c. Could this trait be inherited as a simple x linked recessive?
d. Could this trait be inherited as a simple x linked dominant?
YES
YES
YES
YES
NO
NO
NO
NO