BIOL-2011EL Chapter Notes - Chapter 4: Cream Gene, Genomic Imprinting, Dihybrid Cross

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Copyright © 2014 Pearson Education, Inc.
Essentials of Genetics, 8e (Klug)
Chapter 4 Modification of Mendelian Ratios
1) A mutation in a gene often results in a reduction of the product of that gene. The term for this
type of mutation is ________.
A) codominance
B) incomplete dominance
C) gain of function
D) multiple allelism
E) loss of function or null (in the case of complete loss)
Answer: E
Section: 4.1
2) With incomplete dominance, a likely ratio resulting from a monohybrid cross would be
________.
A) 3:3
B) 1:2:2:4
C) 1:2:1
D) 9:3:3:1
E) 3:1
Answer: C
Section: 4.3
3) The presence of more than two alternative forms of a given gene would be called ________.
A) multiple alleles
B) alternation of generations
C) codominance
D) incomplete dominance
E) hemizygosity
Answer: A
Section: 4.5
4) A condition in which one gene pair masks the expression of a non-allelic gene pair is called
________.
A) codominance
B) epistasis
C) dominance
D) recessiveness
E) additive alleles
Answer: B
Section: 4.8
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Copyright © 2014 Pearson Education, Inc.
5) Typical ratios resulting from epistatic interactions in dihybrid crosses would be ________.
A) 9:3:3:1, 1:2:1
B) 1:1:1:1, 1:4:6:4:1
C) 9:3:4, 9:7
D) 1:2:2:4:1:2:1:2:1, 1:2:1
E) 3:1, 1:1
Answer: C
Section: 4.8
6) With which of the following would hemizygosity most likely be associated?
A) codominance
B) incomplete dominance
C) trihybrid crosses
D) X-linked inheritance
E) sex-limited inheritance
Answer: D
Section: 4.11
7) Because of the mechanism of sex determination, males of many species can be neither
homozygous nor heterozygous. Such males are said to be ________.
A) dominant
B) hemizygous
C) recessive
D) complementary
E) None of the answers listed is correct.
Answer: B
Section: 4.11
8) How many different alleles can a gene have?
Answer: Theoretically, an extremely large number of possibilities exist. Various bases
could change, giving a variety of alleles, and combinations of those changed bases could
provide additional variety.
Section: 4.1
9) Assume that a dihybrid cross (AaBb X AaBb) is made in which the gene loci are autosomal,
independently assorting, and incompletely dominant. What phenotypic ratio would you expect
from such a cross? Just provide the ratio, not the phenotypes.
Answer: 1:2:1:2:4:2:1:2:1
Section: 4.3
10) Assume that a cross is made between two organisms that are both heterozygous for a gene
that shows incomplete dominance. What phenotypic and genotypic ratios are expected in the
offspring?
Answer: 1:2:1
Section: 4.3
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Copyright © 2014 Pearson Education, Inc.
11) Assume that a dihybrid cross is made in which the genes' loci are autosomal, independently
assorting, and incompletely dominant. How many different phenotypes are expected in the
offspring?
Answer: 9
Section: 4.3
12) The trait of medium-sized leaves in iris is determined by the genetic condition PP'. Plants
with large leaves are PP, whereas plants with small leaves are P'P'. A cross is made between two
plants each with medium-sized leaves. If they produce 80 seedlings, what would be the expected
phenotypes, and in what numbers would they be expected? What is the term for this allelic
relationship?
Answer: 20 (large leaves), 40 (medium leaves), 20 (small leaves); incomplete dominance
Section: 4.4
13) The trait for medium-sized leaves in iris is determined by the genetic condition PP'. Plants
with large leaves are PP, whereas plants with small leaves are P'P'. The trait for red flowers is
controlled by the genes RR, pink by RR', and white by R'R'. A cross is made between two plants
each with medium-sized leaves and pink flowers. If they produce 320 seedlings, what would be
the expected phenotypes, and in what numbers would they be expected? Assume no linkage.
Answer: 20 large, red
40 medium, red
20 small, red
40 large, pink
80 medium, pink
40 small, pink
20 large, white
40 medium, white
20 small, white
Section: 4.4
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Document Summary

Chapter 4 modification of mendelian ratios: a mutation in a gene often results in a reduction of the product of that gene. The term for this type of mutation is ________: codominance, incomplete dominance, gain of function, multiple allelism, loss of function or null (in the case of complete loss) Section: 4. 1: with incomplete dominance, a likely ratio resulting from a monohybrid cross would be. Section: 4. 3: the presence of more than two alternative forms of a given gene would be called ________, multiple alleles, alternation of generations, codominance, incomplete dominance, hemizygosity. Section: 4. 5: a condition in which one gene pair masks the expression of a non-allelic gene pair is called. ________: codominance, epistasis, dominance, recessiveness, additive alleles. 1: typical ratios resulting from epistatic interactions in dihybrid crosses would be ________, 9:3:3:1, 1:2:1, 1:1:1:1, 1:4:6:4:1, 9:3:4, 9:7, 1:2:2:4:1:2:1:2:1, 1:2:1, 3:1, 1:1.

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