Name: 
 

Practice Genetics



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

 1) 

What do we mean when we use the terms monohybrid cross and dihybrid cross?
A)
A monohybrid cross involves a single parent, whereas a dihybrid cross involves two parents.
B)
A monohybrid cross produces a single progeny, whereas a dihybrid cross produces two progeny.
C)
A dihybrid cross involves organisms that are heterozygous for two characters and a monohybrid cross involves only one.
D)
A monohybrid cross is performed for one generation, whereas a dihybrid cross is performed for two generations.
E)
A monohybrid cross results in a 9:3:3:1 ratio whereas a dihybrid cross gives a 3:1 ratio.
 

 2) 

How many unique gametes could be produced through independent assortment by an individual with the genotype AaBbCCDdEE?
A)
4
B)
8
C)
16
D)
32
E)
64
 

 3) 

A sexually reproducing animal has two unlinked genes, one for head shape ( H) and one for tail length (T). Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism?
A)
tt
B)
Hh
C)
HhTt
D)
T
E)
HT
 

 4) 

When crossing an organism that is homozygous recessive for a single trait with a heterozygote, what is the chance of producing an offspring with the homozygous recessive phenotype?
A)
0%
B)
25%
C)
50%
D)
75%
E)
100%
 

 5) 

Black fur in mice (B) is dominant to brown fur ( b). Short tails (T) are dominant to long tails ( t). What fraction of the progeny of crosses BbTt ´ BBtt will be expected to have black fur and long tails?
A)
1/16
B)
3/16
C)
3/8
D)
1/2
E)
9/16
 

 6) 

In certain plants, tall is dominant to short. If a heterozygous plant is crossed with a homozygous tall plant, what is the probability that the offspring will be short?
A)
1
B)
1/2
C)
1/4
D)
1/6
E)
0
 

 7) 

In the cross AaBbCc ´ AaBbCc, what is the probability of producing the genotype AABBCC?
A)
1/4
B)
1/8
C)
1/16
D)
1/32
E)
1/64
 

 8) 

Given the parents AABBCc ´ AabbCc, assume simple dominance for each trait and independent assortment. What proportion of the progeny will be expected to phenotypically resemble the first parent?
A)
1/4
B)
1/8
C)
3/4
D)
3/8
E)
1
 

 9) 

In cattle, roan coat color (mixed red and white hairs) occurs in the heterozygous ( Rr) offspring of red (RR) and white (rr) homozygotes. Which of the following crosses would produce offspring in the ratio of 1 red:2 roan:1 white?
A)
red ´ white
B)
roan ´ roan
C)
white ´ roan
D)
red ´ roan
E)
The answer cannot be determined from the information provided.
 
 
The following questions refer to the pedigree chart in Figure 14.2 for a family, some of whose members exhibit the dominant trait, W. Affected individuals are indicated by a dark square or circle.

nar001-1.jpg
 

 10) 

What is the genotype of individual II–5?
A)
WW
B)
Ww
C)
ww
D)
WW or ww
E)
ww or Ww
 

 11) 

What is the likelihood that the progeny of IV–3 and IV–4 will have the trait?
A)
0%
B)
25%
C)
50%
D)
75%
E)
100%
 

 12) 

What is the probability that individual III–1 is Ww?
A)
3/4
B)
1/4
C)
2/4
D)
2/3
E)
1
 
 
Use the following pedigree (Figure 14.3) for a family in which dark-shaded symbols represent individuals with one of the two major types of colon cancer. Numbers under the symbols are the individual’s age at the time of diagnosis.

nar002-1.jpg
 

 13) 

What is the genotype of the deceased individual in generation II?
A)
homozygous for a gene for colon cancer
B)
homozygous for both cancer alleles from his mother
C)
heterozygous for a gene for colon cancer
D)
affected by the same colon cancer environmental factor as his mother
E)
carrier of all of the several known genes for colon cancer
 

 14) 

In each generation of this family after generation I, the age at diagnosis is significantly lower than would be found in nonfamilial (sporadic) cases of this cancer ( ~ 63 years). What is the most likely reason?
A)
Members of this family know to be checked for colon cancer early in life.
B)
Hereditary (or familial) cases of this cancer typically occur at earlier ages than do nonfamilial forms.
C)
This is pure chance; it would not be expected if you were to look at a different family.
D)
This cancer requires mutations in more than this one gene.
E)
Affected members of this family are born with colon cancer, and it can be detected whenever they are first tested.
 

 15) 

From this pedigree, how does this trait seem to be inherited?
A)
from mothers
B)
as an autosomal recessive
C)
as a result of epistasis
D)
as an autosomal dominant
E)
as an incomplete dominant
 

 16) 

The affected woman in generation IV is thinking about her future and asks her oncologist (cancer specialist) whether she can know whether any or all of her children will have a high risk of the same cancer. The doctor would be expected to advise which of the following?
I.     genetic counseling
II.   prenatal diagnosis when/if she becomes pregnant
III.  testing to see whether she has the allele
IV.  testing to see whether her future spouse or partner has the allele
A)
I only
B)
II only
C)
I and II only
D)
I, II, and III only
E)
III and IV only
 
 
Use the following information to answer the questions below.

Two true-breeding stocks of pea plants are crossed. One parent has red, axial flowers and the other has white, terminal flowers; all F1 individuals have red, axial flowers. The genes for flower color and location assort independently.
 

 17) 

If 1,000 F2 offspring resulted from the cross, approximately how many of them would you expect to have red, terminal flowers?
A)
65
B)
190
C)
250
D)
565
E)
750
 

 18) 

Among the F2 offspring, what is the probability of plants with white axial flowers?
A)
9/16
B)
1/16
C)
3/16
D)
1/8
E)
1/4
 
 
Use the following information to answer the questions below.

Radish flowers may be red, purple, or white. A cross between a red-flowered plant and a white-flowered plant yields all-purple offspring. The part of the radish we eat may be oval or long, with long being the dominant characteristic.
 

 19) 

If true–breeding red long radishes are crossed with true–breeding white oval radishes, the F1 will be expected to be which of the following?
A)
red and long
B)
red and oval
C)
white and long
D)
purple and long
E)
purple and oval
 

 20) 

In the F2 generation of the above cross, which of the following phenotypic ratios would be expected?
A)
9:3:3:1
B)
9:4:3
C)
1:1:1:1
D)
1:1:1:1:1:1
E)
6:3:3:2:1:1
 

 21) 

The flower color trait in radishes is an example of which of the following?
A)
a multiple allelic system
B)
sex linkage
C)
codominance
D)
incomplete dominance
E)
epistasis
 

 22) 

Males are more often affected by sex–linked traits than females because
A)
male hormones such as testosterone often alter the effects of mutations on the X chromosome.
B)
female hormones such as estrogen often compensate for the effects of mutations on the X chromosome.
C)
X chromosomes in males generally have more mutations than X chromosomes in females.
D)
males are hemizygous for the X chromosome.
E)
mutations on the Y chromosome often worsen the effects of X–linked mutations.
 

 23) 

In cats, black fur color is caused by an X–linked allele; the other allele at this locus causes orange color. The heterozygote is tortoiseshell. What kinds of offspring would you expect from the cross of a black female and an orange male?
A)
tortoiseshell females; tortoiseshell males
B)
black females; orange males
C)
orange females; orange males
D)
tortoiseshell females; black males
E)
orange females; black males
 

 24) 

What does a frequency of recombination of 50% indicate?
A)
The two genes are likely to be located on different chromosomes.
B)
All of the offspring have combinations of traits that match one of the two parents.
C)
The genes are located on sex chromosomes.
D)
Abnormal meiosis has occurred.
E)
Independent assortment is hindered.
 

 25) 

Recombination between linked genes comes about for what reason?
A)
Mutation on one homolog is different from that on the other homolog.
B)
Independent assortment sometimes fails because Mendel had not calculated appropriately.
C)
When genes are linked they always "travel" together at anaphase.
D)
Crossovers between these genes result in chromosomal exchange.
E)
Nonrecombinant chromosomes break and then re–join with one another.
 

 26) 

Mitochondrial DNA is primarily involved in coding for proteins needed for electron transport. Therefore, in which body systems would you expect most mitochondrial gene mutations to be exhibited?
A)
the immune system and the blood
B)
the excretory and respiratory systems
C)
the skin and senses
D)
the nervous and muscular systems
E)
the circulation system
 

 27) 

The following is a map of four genes on a chromosome.

mc027-1.jpg

Between which two genes would you expect the highest frequency of recombination?
A)
A and W
B)
W and E
C)
E and G
D)
A and E
E)
A and G
 

 28) 

mc028-1.jpg

The pedigree in Figure 15.3 shows the transmission of a trait in a particular family. Based on this pattern of transmission, the trait is most likely
A)
mitochondrial.
B)
autosomal recessive.
C)
sex–linked dominant.
D)
sex–linked recessive.
E)
autosomal dominant.
 
 
Refer to the following information to answer the questions below.

A man who is an achondroplastic dwarf with normal vision marries a color–blind woman of normal height. The man’s father was 6 feet tall, and both the woman’s parents were of average height. Achondroplastic dwarfism is autosomal dominant, and red-green color blindness is X–linked recessive.
 

 29) 

How many of their daughters might be expected to be color–blind dwarfs?
A)
all
B)
none
C)
half
D)
one out of four
E)
three out of four
 

 30) 

What proportion of their sons would be color–blind and of normal height?
A)
none
B)
half
C)
one out of four
D)
three out of four
E)
all
 

 31) 

They have a daughter who is a dwarf with normal color vision. What is the probability that she is heterozygous for both genes?
A)
0%
B)
25%^
C)
50%
D)
75%
E)
100%
 
 
Use the following information to answer the questions below.

A plantlike organism on the planet Pandora can have three recessive genetic traits: bluish leaves, due to an allele ( a) of gene A; a feathered stem, due to an allele (b) of gene B; and hollow roots due to an allele (c) of gene C. The three genes are linked and recombine as follows:

A geneticist did a testcross with an organism that had been found to be heterozygous for the three recessive traits and she was able to identify progeny of the following phenotypic distribution (+ = wild type):

nar006-1.jpg
 

 32) 

Which of the following are the phenotypes of the parents in this cross?
A)
2 and 5
B)
1 and 6
C)
4 and 8
D)
3 and 7
E)
1 and 2
 

 33) 

In which progeny phenotypes has there been recombination between genes  A and B?
A)
1, 2, 5, and 6
B)
1, 3, 6, and 7
C)
2, 4, 5, and 8
D)
2, 3, 5, and 7
E)
in all 8 of them
 

 34) 

If recombination is equal to distance in centimorgans (cM), what is the approximate distance between genes A and B?
A)
1.5 cM
B)
3 cM
C)
6 cM
D)
15 cM
E)
30 cM
 

 35) 

What is the greatest benefit of having used a testcross for this experiment?
A)
The homozygous recessive parents are obvious to the naked eye.
B)
The homozygous parents are the only ones whose crossovers make a difference.
C)
Progeny can be scored by their phenotypes alone.
D)
All of the progeny will be heterozygous.
E)
The homozygous recessive parents will be unable to cross over.
 

 36) 

The greatest distance among the three genes is between a and c. What does this mean?
A)
Gene a is closest to b.
B)
Genes are in the order: a–b–c.
C)
Gene a is not recombining with c.
D)
Gene a is between b and c.
E)
Distance ab is equal to distance ac.
 

Essay
 

 1) 

Chi Squared Review Quiz

In fruit flies, red eyes and vestigial (stubby) wings are recessive traits.  Suppose a fruit fly geneticist performed the following cross:
Cross # 1
Homozygous recessive crossed with true breeding dominant phenotype
Cross #2
Homozygous recessive crossed with offspring of Cross #1 (F1 generation).
The following results were observed in the F2 generation;
      420 wild type eyes and wings (black eyes, long wings)
      410 red eyed, vestigial winged flies
      83 black eyed, vestigial winged flies
      87 red eyed, normal winged flies.

Statistically are these results as expected (given dominant and recessive hereditary patterns)?
If not, what could have happened?

Link to Chi Squared Critical Values;
http://jungminded.weebly.com/uploads/1/3/5/8/13582285/1305496_orig.png

Chi Squared formula;
x2 = summation of (observed -expected) 2 / expected

EC - Who or which lab might have first performed this cross and analysis??
 



 
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