BIOL-2011EL Chapter Notes - Chapter 7: Malate Dehydrogenase, Centimorgan, Synapsis

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Copyright © 2014 Pearson Education, Inc.
Essentials of Genetics, 8e (Klug)
Chapter 7 Linkage and Chromosome Mapping in Eukaryotes
1) When two genes fail to assort independently, the term normally applied is ________.
A) discontinuous inheritance
B) Mendelian inheritance
C) linkage
D) tetrad analysis
E) dominance and/or recessiveness
Answer: C
Section: Introduction
2) Assume that a cross is made between AaBb and aabb plants and that the offspring fall into
approximately equal numbers of the following groups: AaBb, Aabb, aaBb, aabb. These results
are consistent with ________.
A) independent assortment – equal proportions of each is the key terms
B) alternation of generations
C) complete linkage
D) incomplete dominance
E) hemizygosity
Answer: A
Section: 7.1
3) Assume that a cross is made between AaBb and aabb plants and that all the offspring are
either AaBb or aabb. These results are consistent with ________.
A) complete linkage
B) alternation of generations
C) codominance
D) incomplete dominance
E) hemizygosity
Answer: A
Section: 7.2
4) Assume that a cross is made between AaBb and aabb plants and that the offspring occur in the
following numbers: 106 AaBb, 48 Aabb, 52 aaBb, 94 aabb. These results are consistent with
________.
A) sex-linked inheritance with 30% crossing over
B) linkage with 50% crossing over
C) linkage with approximately 33 map units between the two gene loci
D) independent assortment
E) 100% recombination
Answer: C
Section: 7.2
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Copyright © 2014 Pearson Education, Inc.
5) The phenomenon in which one crossover decreases the likelihood of crossovers in nearby
regions is called ________.
A) chiasma
B) negative interference
C) reciprocal genetic exchange
D) positive interference
E) mitotic recombination
Answer: D
Section: 7.4
6) Methods for determining the linkage group and genetic map in humans involve ________.
A) DNA markers
B) twin spots and tetrad analysis
C) tetrad analysis and bromodeoxyuridine
D) zygotene and pachytene DNA synthesis
E) chiasmatype and classical analyses
Answer: A
Section: 7.5
7) In the early 1900s, two scientists noted that there were many more genes than chromosome
pairs, thus setting the stage for the suggestion that some gene loci might be linked during meiotic
processes. Who were these two scientists?
Answer: Walter Sutton and Theodor Boveri
Section: Introduction
8) What is the expected evolutionary significance of genetic recombination?
Answer: production of genetic variation
Section: Introduction
9) Under what circumstance might two loci be on the same chromosome but behave as if
independently assorting in crosses?
Answer: If the genes are far apart, they may show independent assortment.
Section: 7.1
10) At what stage of the meiotic cell cycle and during what chromosomal configuration does
crossing over occur?
Answer: at the four-strand stage of meiosis, after synapsis of homologous chromosomes,
and before the end of prophase I
Section: 7.1
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Copyright © 2014 Pearson Education, Inc.
11) Diagram chromosomal events that will ultimately result in the segregation of alleles (A and
a) during meiosis II rather than meiosis I.
Answer:
Section: 7.2
12) What is the relationship between the degree of crossing over and the distance between two
genes?
Answer: It is direct: as the distance increases, the frequency of recombination increases.
Section: 7.2
13) The genes for mahogany eyes and ebony body are approximately 25 map units apart on
chromosome III in Drosophila. Assume that a mahogany-eyed female was mated to an ebony-
bodied male and that the resulting F1 phenotypically wild-type females were mated to
mahogany, ebony males. Of 1000 offspring, what would be the expected phenotypes, and in
what numbers would they be expected?
Answer: mahogany = 375; ebony = 375; wild-type = 125; mahogany-ebony = 125
Section: 7.3
14) Assume that there are 12 map units between two loci in the mouse and that you are able to
microscopically observe meiotic chromosomes in this organism. If you examined 200 primary
oocytes, in how many would you expect to see a chiasma between the two loci?
Answer: 48
Section: 7.3
15) Phenotypically wild-type F1 female Drosophila, whose mothers had light eyes (lt) and
fathers had straw (stw) bristles, produced the following offspring when crossed to homozygous
light-straw males:
Phenotype Number
light-straw 22
wild-type 18
light 990
straw 970
Total: 2000
Compute the map distance between the light and straw loci.
Answer: 2 map units
Section: 7.3
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Document Summary

Chapter 7 linkage and chromosome mapping in eukaryotes: when two genes fail to assort independently, the term normally applied is ________, discontinuous inheritance, mendelian inheritance, linkage, tetrad analysis, dominance and/or recessiveness. Section: introduction: assume that a cross is made between aabb and aabb plants and that the offspring fall into approximately equal numbers of the following groups: aabb, aabb, aabb, aabb. These results are consistent with ________: independent assortment equal proportions of each is the key terms, alternation of generations, complete linkage, incomplete dominance, hemizygosity. Section: 7. 1: assume that a cross is made between aabb and aabb plants and that all the offspring are either aabb or aabb. These results are consistent with ________: complete linkage, alternation of generations, codominance, incomplete dominance, hemizygosity. Section: 7. 2: assume that a cross is made between aabb and aabb plants and that the offspring occur in the following numbers: 106 aabb, 48 aabb, 52 aabb, 94 aabb.

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